GE PowerVac GEK-86132G User manual

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GEK-86132G Instructions
g
PowerVac ® Vacuum Circuit Breaker
with ML-18 or ML-18H Mechanism
__
_______________________________________________________________________________

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PowerVac ®Vacuum Circuit Breaker
With ML-18 or ML-18H Mechanism
Table of Contents
Description Page
SECT ON 1 ntroduction.............................................. 4
1.1 Safety .............................................................................. 4
1.2 Maintenance ................................................................... 4
SECT ON 2 Description................................................ 5
2.1 General............................................................................ 5
2.2 Summary Description ...................................................... 5
SECT ON 3 Receiving, Handling and
Storage...................................................... 5
3.1 Receiving ........................................................................ 5
A. quipment Packages................................................. 5
B. Inspecting for Damage .............................................. 5
C. Filing a Claim ............................................................. 5
3.2 Handling .......................................................................... 5
3.3 Storage............................................................................ 5
SECT ON 4 Features....................................................... 6
4.1 Safety Precautions........................................................... 6
4.2 Interlocks......................................................................... 6
4.2.1 Rating Interference Plate................................................. 6
4.2.2 Closing Spring Interlock ................................................... 7
4.2.3 Negative Interlock............................................................ 7
4.2.4 Positive Interlock Bar....................................................... 7
4.2.5 Closing Spring Gag Interlock............................................ 7
SECT ON 5 Operation ................................................... 8
5.1 General............................................................................ 8
5.2 Close Spring Charging ..................................................... 8
5.3 Closing Operation............................................................ 8
5.4 Opening Operation.......................................................... 9
5.5 Trip-free Operation.......................................................... 9
SECT ON 6 Control Circuit........................................ 9
SECT ON 7 Mechanical Checking and
Slow Closing......................................... 9
7.1 Visual Inspection.............................................................. 9
7.2 Closing Spring Charging ..................................................10
7.3 Closing Spring Gag ..........................................................10
7.4 Slow Closing....................................................................10
7.5 Gag Plate Removal..........................................................10
SECT ON 8 Dimensional Checks..........................11
8.1 Primary Contact rosion ..................................................11
8.2 ML-18 Wipe Spring Compression....................................11
8.3 ML-18H Wipe Spring Compression .................................11
8.4 Contact Gap ....................................................................11
8.5 Coil Plunger Gap..............................................................11
8.6 Control Switch Adjustment..............................................12
8.6.1 LCS and SM/LS Switch Adjustment.................................12
8.6.2 CL/MS Switch Adjustment ..............................................12
8.6.3 IL/MS Switch Adjustment................................................13
Description Page
SECT ON 9 Electrical Checks .................................. 14
9.1 lectrical Operation......................................................... 14
9.2 High Potential Test.......................................................... 14
9.2.1 Primary Circuit................................................................. 14
9.2.2 Secondary Circuit ............................................................ 14
9.3 Primary Circuit Resistance .............................................. 14
9.4 Vacuum Interrupter Integrity Test.................................... 14
9.5 Insulation Test................................................................. 15
SECT ON 10 Checking and nstalling
Breakers................................................. 16
SECT ON 11 Maintenance......................................... 17
11.1 General ........................................................................... 17
11.1.1 PowerVac Interrupter ...................................................... 17
11.1.2 Trouble Reporting ........................................................... 17
11.2 Service Conditions .......................................................... 17
11.3 Fault Interruptions ........................................................... 17
11.4 Contact rosion............................................................... 17
11.5 Transfer Finger Wear ...................................................... 17
11.6 Mechanism ..................................................................... 17
11.7 Primary Insulation Parts................................................... 17
11.8 Lubrication ...................................................................... 18
11.9 Recommended Maintenance.......................................... 18
SECT ON 12 Timing........................................................ 19
SECT ON 13 Opening and Closing Speed ... 20
SECT ON 14 Repair and Replacement............ 21
14.1 General ........................................................................... 21
14.2 Replacement of Interrupter Assemblies ......................... 21
14.3 Primary Disconnect Fingers ............................................ 21
14.4 Mechanism ..................................................................... 21
14.5 Control Switches............................................................. 21
14.6 Trip Coil Replacement..................................................... 21
14.7 Closing Coil Replacement............................................... 22
14.8 Auxiliary Switch Replacement......................................... 22
14.9 Motor Replacement........................................................ 22
14.10 “Y” Relay Replacement................................................... 22
SECT ON 15 Renewal Parts ..................................... 23
15.1 Ordering Instructions....................................................... 23
SECT ON 16 Mechanical Adjustment.............. 23
16.1 General ........................................................................... 23
16.2 Wipe Adjustment ............................................................ 23
16.3 Contact Gap Adjustment................................................. 23
16.4 Trip Coil Plunger.............................................................. 24
16.5 Close Coil Plunger........................................................... 24
16.6 Close Latch Stop Bolt...................................................... 24
16.7 Closing Spring Discharge Interlock .................................. 24
16.8 Negative Interlock ........................................................... 24
NDEX ........................................................................................ 37
Trouble Reporting Form................................................................ 39

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List of llustrations
Figure Page
1 Front view of PowerVac® breaker with front cover ................... 6
2 Rating interference plate........................................................... 6
3 Front view of PowerVac breaker without front cover ................ 8
4 Manual charging........................................................................ 9
5 Gag plate installation .................................................................10
6 Operating rod assembly ............................................................10
7 Contact gap...............................................................................11
8 Breaker turned on right side......................................................11
9 Close coil plunger gap ...............................................................12
10 Trip coil plunger gap..................................................................12
11 Control switches .......................................................................13
12 Sample operating speed graphs................................................19
13 Contact gap adjustment ............................................................20
14 Auxiliary switch position ............................................................22
15 Spring discharge interlock .........................................................24
16 Toggle linkage positions of the ML-18 mechanism ...................25
17 Schematic of ML-18 mechanism...............................................27
18 Typical wiring diagram for ML-18 mechanism...........................29
19 PowerVac® breaker left-front view ............................................30
20 PowerVac® breaker right-rear view ...........................................30
21 Trip coil and linkage...................................................................31
22 Close coil linkage.......................................................................32
23 Bottom view of the ML-18 mechanism.....................................33
24 Flex cable connections..............................................................34
25 Negative interlock .....................................................................34
26 Close latch stop.........................................................................35
27 Wipe spring...............................................................................35
Table Page
1 Control Device and Voltage..................................................... 18
2 Measurements ....................................................................... 36
3 Adjustments............................................................................ 36
THESE INSTRUCTIONS ARE INTENDED FOR USE BY QUALIFIED PERSONNEL FOR INSTRUCTION AND MAINTENANCE PURPOSES.
REPRODUCTION IN WHOLE OR IN PART IS NOT PERMITTED WITHOUT THE EXPRESS PERMISSION OF GENERAL ELECTRIC.

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PowerVac
®Vacuum Circuit Breaker
With ML-18 or ML-18H Mechanism
SECT ON 1— ntroduction
This manual provides the information needed by the user to
properly install, operate and maintain the ML-18 or ML-18H
PowerVac® Breaker.
The PowerVac® vacuum breaker is a horizontal drawout,
removable and interchangeable interrupting element for use
in metalclad switchgear to provide protection and control of
electrical apparatus and power systems. To the extent
required applicable ANSI, I and N MA Standards are met.
No such assurances are given with respect to local codes and
ordinances, as they vary greatly.
1.1—Safety
ach user must maintain a safety program for the protection
of personnel, as well as other equipment, from the potential
hazards associated with electrical equipment.
The following requirements are intended to augment the
user's safety program, but NOT supplant the user's
responsibility for devising a complete safety program. The
following basic industry practiced safety requirements are
applicable to all major electrical equipment such as switchgear
or switchboards. G neither condones nor assumes any
responsibility for practices which deviate from the following:
1. ALL CONDUCTORS MUST B ASSUM D TO B
N RGIZ D UNL SS TH IR POT NTIAL HAS B N
M ASUR D AS GROUND AND AD QUAT CAPACITY
GROUNDING ASS MBLI S HAV B N APPLI D TO
PR V NT N RGIZING. Many accidents have been
caused by unplanned energization from non-recognized
back feeds, equipment malfunctions, and from a wide
variety of sources.
2. VACUUM CIRCUIT BR AK RS AR NOT TO B
CONSID R D AS AN ISOLATING M ANS FOR
PROVIDING SAF TY TO P RSON L UNL SS
WITHDRAWN TO FULLY “DISCONN CT D/T ST”
POSITION. In the “CONN CT D” position with the
interrupter contacts separated (breaker open), small
leakage current with high voltages can flow across the
gap. In addition, leakage current can flow across the
bottle or interrupter assembly if dirty or high humidity is
providing a path for tracking.
3. It is strongly recommended that all equipment be
completely de-energized, verified to be “dead”, then
grounded with adequate capacity grounding assemblies
prior to any maintenance. The grounding cable
assemblies must be able to withstand energizing fault
levels so that protective equipment may clear the circuit
safely. Additional discussion on this concept is covered in
Chapter 20 of ANSI/NFPA 70B, lectrical quipment
Maintenance.
4. Although interlocks to reduce some of the risks are
provided, the individual's actions while performing service
or maintenance are essential to prevent accidents. ach
person's knowledge; mental awareness; and planned and
executed actions often determine if an accident will
occur. The most important method of avoiding accidents
is for all associated personnel to carefully apply a
thorough under-standing of the specific equipment from
the viewpoints of its purpose, its construction, its
operation and the situations which could be hazardous.
All personnel associated with installation, operation and
maintenance of electrical equipment, such as power circuit
breakers and other power handling equipment, must be
thoroughly instructed, with periodic retraining, regarding
power equipment in general as well as the particular model of
equipment with which they are working.
Instruction books, actual devices and appropriate safety and
maintenance practices such as OSHA publications, National
lectric Safety Code (ANSI C2), National lectric Code, and
National Fire Protection Association (NFPA) 70B lectrical
quipment Maintenance must be closely studied and
followed. During actual work, supervision should audit
practices to assure conformance.
1.2—Maintenance
xcellent maintenance is essential for reliability and safety of
any electrical equipment. Maintenance programs must be
tuned to the specific application, well planned and carried out
consistent with both industry experience and manufacturer's
recommendations. Local environment must always be
considered in such programs, including such variables as
ambient temperatures, extreme moisture, number of
operations, corrosive atmosphere or major insect problems
and any other unusual or abusive condition of the application.
One of the critical service activities, sometimes neglected,
involves the calibration of various control devices. These
monitored conditions in the primary and secondary circuits,
sometimes initiating emergency corrective action such as
opening or closing circuit breakers. In view of the vital role of
these devices, it is important that a periodic test program be
followed. As was outlined above, it is recognized that the
interval between periodic checks will vary depending upon
environment, the type of device and the user's experience.
It is the G recommendation that, until the user has
accumulated enough experience to select a test interval
better suited to the individual requirements, all significant
calibrations be checked at an interval of one to two years.
To accomplish this, some devices can be adequately tested
using test sets. Specific calibration instructions on particular
devices typically are provided by supplied instruction books.
Instruction books supplied by manufacturers address
components that would normally require service or
maintenance during the useful life of the equipment.
However, they can not include every possible part that could
under adverse environments. Maintenance personnel must
be alert to deterioration of any part of the supplied
switchgear, taking actions, as necessary to restore it to
serviceable status.
Industry publications of recommended maintenance practices
such as ANSI/NFPA 70B, lectrical quipment Maintenance,

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should be carefully studied and applied in each user's
formation of planned maintenance.
Some users may require additional assistance from G in the
planning and performance of maintenance. Local G Sales
can be contracted to either undertake maintenance or to
provide technical assistance such as the latest publications.
The performance and safety of all equipment may be
compromised by the modification of supplied parts or their
replacement by non-identical substitutes. All such design
changes must be qualified to the original manufacturers
specifications.
The user should methodically keep written maintenance
records as an aid in future service planning and equipment
reliability improvement. Unusual experiences should be
promptly communicated to G. .
SECT ON 2—Description
2.1—General
This section contains a description of the PowerVac® vacuum
circuit breaker. It also describes the functions of the electrical
and mechanical systems.
2.2—Summary Description
The PowerVac® vacuum circuit breaker uses sealed vacuum
power interrupters to establish and interrupt a primary circuit.
Primary connections to the associated metalclad switchgear
are made by horizontal bars and disconnect fingers,
electrically and mechanically connected to the vacuum
interrupters. Molded interrupter supports, one per phase on a
three-phase circuit breaker, provide mountings for the primary
bars, interrupters, current transfer fingers, and heat
dissipation fins (where used). The operating mechanism
provides direct motion at each phase location in order to
move the movable contact of the vacuum interrupters from an
open position to a spring-loaded closed position and then back
to the open position on command.
The ML-18 and ML-18H mechanisms are of the stored-energy
type and use a gear motor to charge a closing spring. During a
closing operation, the energy stored in the closing spring is
used to close the vacuum interrupter contacts, compress the
wipe springs which load the contacts, charge the opening
spring, and overcome bearing and other friction forces, The
energy then stored in the wipe springs and opening spring will
open the contacts during an opening operation.
Closing and opening operations are controlled electrically by
the metalclad switchgear or remote relaying. Mechanical
control is provided by manual close and trip buttons on the
circuit breaker. The closing spring may be manually charged,
and a method for slow-closing the primary contacts is
available. The mechanism will operate at the ac or dc voltage
indicated on the circuit breaker nameplate.
Mechanical and electrical interlocks are provided and are
described in Section 4.2, Interlock.
SECT ON 3—Receiving, Handling and Storage
3.1—Receiving
A. Equipment Packages
very package leaving the factory is plainly marked with the
case number, requisition number, and customer’s order
number. If the equipment has been split for shipment, the
section numbers of the equipment enclosed in each shipping
package are identified.
NOTE: To avoid loss of any parts when unpacking, the
contents of each container should be carefully checked
against the packing list before discarding the packing material.
Contents of each shipping package are listed on the Master
Packing List. In addition, this list includes the number of the
shipping crate in which miscellaneous parts needed to install
and operate equipment (such as hardware, contact lubricant,
touch-up paint, breaker closing devices, etc.) are located.
Normally, such devices are packed in a cardboard carton and
the carton secured in an empty switchgear compartment. If
such items are packed in a switchgear section instead of a
separate crate, the list will indicate appropriate section
number in which they are stored. Large items (such as
breaker lift trucks used with indoor and outdoor equipment)
will always be shipped in separate crates or cartons.
B. nspecting for Damage
All equipment leaving the factory is carefully inspected and
packed by personnel experienced in the proper handling and
packing of electrical equipment. Upon receipt of any
equipment, immediately perform a visual inspection to
ascertain if any damage has been sustained in shipping or if
there are any loose parts.
C. Filing a Claim
If any damage is evident, or indication of rough handling is
visible, file a claim for damage at once with the transportation
company and notify the nearest General Electric Company
Sales Office immediately. Information on damaged parts, part
number, case number, requisition number, etc., should
accompany the claim.
3.2—Handling
When lifting the breaker, use of the specially designed lift
truck is recommended. It is necessary to use the lift truck
when placing a breaker into or removing it from the metalclad
switchgear unless the breaker is equipped with a roll-in
undercarriage (bottom only) . If it is necessary to lift the
breaker with a hoist use four 1/2 inch diameter hooks rated at
least 500 pounds each. Lifting locations are provided in the
side frame members. Use a spreader wider than the breaker
to prevent slings from contacting the interrupter supports.
3.3—Storage
It is recommended that the breaker be put immediately in its
permanent location. If this is not possible, the following
precautions must be taken to assure proper breaker storage.

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1. The breaker should be protected against condensation,
preferably by storing it in a warm dry room of moderate
temperature such as 40° - 100°F. Circuit breakers for
outdoor metalclad switchgear should be stored in the
equipment only when power is available and the heaters
are in operation to prevent condensation.
2. The breaker should be stored in a clean location, free
from corrosive gases or fumes; particular care, for
example, should be taken to protect the equipment from
moisture and cement dust, as this combination is present
at construction sites and has a very corrosive effect on
many parts.
3. Rollers, latches, etc., of the operating mechanism should
be coated with 0282A2048P009 grease to prevent
rusting.
If the breaker is stored for any length of time, it should be
inspected periodically to see that rusting has not started and
to ensure good mechanical condition. Should the breaker be
stored under unfavorable atmospheric conditions, it should be
cleaned and dried out before being placed in service.
SECT ON 4—Features
4.1—Safety Precautions
This circuit breaker uses powerful springs for energy storage.
WARNING: DO NOT WORK ON TH INT RRUPT RS OR TH
M CHANISM UNL SS TH CIRCUIT BR AK R IS IN TH
“OP N” POSITION AND BOTH TH CLOSING AND OP NING
SPRINGS AR ITH R “DISCHARG D” OR GAGG D AND ALL
L CTRICAL POW R IS R MOV D.
These precautions are required to prevent accidental operation.
Anyone working on the circuit breaker should be familiar with
the contents of this instruction book.
Figure 1 Front view of PowerVac breaker
with front cover
1. Front cover 6. Manual charge lever
2. Cover mounting bolts 7. Counter
3. Manual trip button 8. Spring charge indication
4. Manual close button 9. Closing spring gag access
5. Nameplate 10. Open/Close indicator
The circuit breaker has been shipped in the “CLOS D” position.
After removing packing material, open the breaker by pushing in
firmly on the manual trip button (item 3, Figure 1), while
keeping hands away from moving parts, and verify that the
operation counter advances one count.
Closing and opening springs are now in their discharged
positions. Check this by first pressing the manual close button,
then the manual trip button. The indicator flags on the front of
the breaker should show “OP N” and “DISCHGD”. All
mechanical and electrical checks should be completed before
putting breakers in service.
4.2— nterlocks
ach PowerVac® vacuum circuit breaker is provided with the
following interlocks:
4.2.1 Rating nterference Plate
This interlock (item1, Figure 2) permits only a breaker with a
matching continuous current, voltage and interrupting rating to
be inserted into a metalclad compartment of identical rating.
1. Rating interference plate
2. Lifting locations (3/4” dia. hole at all four corners)
An option available is the combination 1200/2000 ampere
breaker, which can be used in either a 1200 or 2000 ampere
compartment. The rating interference plate must be adjusted to
match the current rating of the compartment. This adjustment is
done by positioning the outer interference plate so that the
edge of the plate lines up with the current indicated on the label
attached to the breaker just above the rating interference plate.
Figure 2 Rating interference plate
2
1
3
5
1
2
4
6
7
8
9
10
2
2 2

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4.2.2 Closing spring interlock
This racking-track operated interlock (item 4, Figure 20)
prevents racking into or out of the metalclad compartment a
breaker that has the closing spring charged. This action is
accomplished by a roller on the right side of the breaker.
Mechanism, which contacts the racking mechanism and
discharges the closing spring, unless the breaker is in the
“DISCONN CT/T ST” position or the “CONN CT” position in
the metalclad compartment. This interlock also opens the
CL/MS switch in the motor circuit to prevent electrical
charging of the closing spring when the breaker is between
the “DISCONN CT/T ST” and “CONN CT” position in the
metalclad compartment.
4.2.3 Negative nterlock
The function of this racking-track operated interlock (item5,
Figure 19) is to remove the trip latch from the trip roller
thereby preventing a closing operation. The interlock also
opens the LCS switch in the closing circuit thereby removing
the close circuit power. The negative trip interlock is
functional while the beaker is being moved between the
“DISCONN CT/T ST” and “CONN CT” position and upon
withdrawal from the metalclad compartment.
4.2.4 Positive nterlock Bar
This interlock will prevent the racking of a closed breaker into
or out of a metalclad compartment. A linkage connected to
the cross shaft extends a détente angle (item 3, Figure 19)
out through the left side of the mechanism frame when the
breaker contacts are in the closed position. If the breaker is in
the “CONN CT” or “DISCONN CT/T ST” position in the
metalclad the détente angle locks into the racking mechanism
to prevent access to the hex section of the racking screw.
4.2.5 Closing Spring Gag nterlock
The interlock is provided to prevent a breaker that has a
gagged closing spring from entering a metalclad unit. This
function is accomplished by projecting an angle (item1, Figure
19) out of the left front side of the mechanism when the
closing spring is gagged. This angle will interfere with the
racking mechanism and block entry into the metalclad unit
when the Closing Spring Gag Access Door is open.

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SECT ON 5—Operation
5.1—General
The PowerVac® vacuum circuit breaker uses sealed vacuum
power interrupters to establish and interrupt a primary circuit.
Primary connections to the associated metalclad switchgear are
made by horizontal bars and disconnect fingers, electrically and
mechanically connected to the vacuum interrupters. Molded
interrupter supports, one per phase on a three-phase circuit
breaker, provide mountings for the primary bars, interrupters,
current transfer fingers, and heat dissipation fins (where used).
The operating mechanism provides direct motion at each phase
location in order to move the lower contact of the vacuum
interrupters from an open position to a spring-loaded closed
position and then back to the open position on command.
The ML-18/18H mechanism (Figure 17) is of the stored-energy
type and uses a gearmotor to charge a closing spring. During a
closing operation, the energy stored in the closing spring is used
to close the vacuum interrupter contacts, compress the wipe
springs which load the contacts, charge the opening spring, and
overcome bearing and other friction forces, The energy then
stored in the wipe springs and opening spring will open the
contacts during an opening operation.
Closing and opening operations are controlled electrically by the
metalclad switchgear or remote relaying. Mechanical control is
provided by manual close and trip buttons on the circuit breaker.
The closing spring may be manually charged, and a method for
slow-closing the primary contacts is available. The mechanism
will operate at the ac or dc voltage indicated on the circuit
breaker nameplate.
5.2—Close Spring Charging
Figure 17 shows a front view of the ML-18 in a schematic form.
The primary contacts are open and the closing spring is charged.
The closing spring charging system consists of a closing spring
(item 1, view B) mounted on the left side of the breaker and the
electrical charging system mounted on the right side of the
breaker. Both components are fastened to the cam shaft (item
2, view B). A manual charging system (item 3, view A) is
provided so that the mechanism can be slow closed and the
closing spring can be charged if there is a loss of electrical
control power.
Spring charging is accomplished electrically by a rotating
eccentric on the output shaft of the gear motor driving pivoted
charging arms (item 4, view C) which oscillate about the
centerline of a ratchet wheel (item 5, view C). A driving pawl
(item 6, view C), mounted within the charging arms, oscillates
with the charging arms. Starting from its rear-most position, as
the charging arms rotate forward, a spring forces engagement
of the driving pawl with a tooth of the ratchet wheel. The
ratchet wheel is advanced by the rotating charging arms and
pawl assembly. Advancement of one tooth spacing is provided
for each oscillation of the system. The ratchet motion is
restricted to one direction by a spring-loaded holding pawl that
prevents the ratchet wheel from going backwards as the
charging arms oscillate back to pick up the next tooth. Thirteen
complete cycles of the charging arms are needed for a full
charge of the closing spring. The efficient, compact gear motor
accomplishes this action in about two seconds. When the
charging cycle is complete, the ratchet wheel is positioned so
that a missing tooth is adjacent to the driving pawl and any
motor over spin will not drive the ratchet wheel, thus preventing
damage to the system.
When the spring is completely charged, the assembly is
retained in that position by the close latch, until it is desired
to close the circuit breaker.
The closing coil cannot be electrically energized unless the
closing spring is completely charged. This action is prevented by
the 52/CHG switch in the closing circuit.
The manual charging system (item 3, view A) works directly on
the cam shaft where a one-way clutch (item 7, view A), driven
by a manual handle, provides rotation of the ratchet wheel.
Manual pumping of the handle advances the ratchet wheel and
the holding pawl prevents counter-rotation while the handle is
returning for another stroke. Approximately eight complete
strokes of the manual handle are required for one complete
spring-charging operation. When the spring charge indicator
(item 9, Figure 3) shows “CHARG D”, MANUAL CHARGING
MUST B DISCONTINU D TO AVOID M CHANISM DAMAG .
Figure 3 Front view of PowerVac breaker
without front cover
1. Upper interrupt connection 8. Counter
2. Interrupter support 9. Spring charge indication
3. Operating rod 10. Manual charge lever
4. Racking arm 11. Manual close button
5. Compartment track rollers 12. Secondary disconnect
6. Manual trip button handle
7. Open/Close indicator 13. Closing spring gag access
5.3—Closing Operation (Refer to Figure 17)
By either energizing the close solenoid or depressing the
manual close button, the close latch (item 8, view C) is rotated,
releasing the closing spring (item 1, view B). This
action releases the energy in the closing spring and transmits it
to the closing cam (item 9, view D) and closing roller (item 10,
view D) and causes the linkage to rise until the prop (item 11,
view D) can slip under the close roller (item 10, view D) and
hold the linkage in place. As the linkage moves, the output crank
(item 12, view D) rotates the cross shaft (item 13, view D)
which in turn rotates the phase bell cranks and compresses the
two opening springs (item 15, view ) on poles 1 and 3, this
closes the vacuum interrupters, and compresses the wipe
springs (item 16, view ) on each pole.
The rotation of the cross shaft (item 13, view D) also changes
the auxiliary switch (item 7, view D) position. The position flag
on the front panel will then indicate “CLOS D”. After the breaker
6
5
4
1
2
12
3
4
8
11
10
7
9
13

9
is closed, the charging motor is again energized and the closing
spring is charged as described under “CLOS D SPRING
CHARGING”. Spring charging is possible when the breaker is in
the closed position because the linkage is held in place by the
prop.
5.4—Opening Operation (refer to Figure 17)
By either energizing the trip solenoid or depressing the manual
trip button (item 23, view B), the trip latch (item 19, view D) is
rotated, permitting the linkage to collapse and the vacuum
interrupter contacts to open under the force of the wipe springs
(item 16, view ) and opening springs (item 15, view ). At the
end of the opening stroke, the center phase wipe spring
assembly hits a stop block on the frame that limits overtravel
and rebound. Rotation of the cross shaft from the closed to the
open position operates the auxiliary switch (item 17, view D)
which opens the trip coil circuit. If the closing spring has been
recharged, the linkage will be reset and the trip latch will be in
place on the trip roller, ready for another closing operation.
5.5—Trip-free Operation
The linkage is mechanically trip free in any location on the
closing stroke. lectrically energizing the trip coil while closing
will, after the auxiliary switch contacts change position, rotate
the trip latch and permit the circuit breaker to open fully.
The linkage will reset as in a normal open operation, and the
closing spring will recharge as described under SPRING
CHARGING.
SECT ON 6—Electric Control circuit
A typical PowerVac® circuit breaker ML-18 or ML-18H mechanism
wiring diagram is shown in Figure 16. Check the wiring diagram
supplied with the actual circuit breaker for its wiring.
The close spring-charging motor circuit is established through
the CL/MS (close latch monitor switch) switch if the close latch
is reset and the SM/LS (spring motor limit switch) if the closing
spring is discharged. When the closing spring is charged, the
SM/LS interrupts the circuit.
The IL/MS switch is connected to sense position of negative
interlock. When the breaker is racked between the connect and
disconnect position, the negative interlock roller is depressed as
a result the IL/MS switch is open and does not allow the motor
to charge the closing spring. Once the breaker is rack in the
switch closes allowing the spring charge motor to charge the
closing spring.
The close coil circuit is established through two normally closed
52Y relay contacts, and the latch-checking switch LCS, if the trip
latch is reset. An auxiliary switch contact 52b is also in series
with the close coil and closes when the breaker is
open and opens when the breaker is closed. During a close
operation, cam rotation closes the SM/LS contact allowing the
52Y relay to be energized; opening its contacts in the close coil
circuit and sealing itself in through one of its own contacts to
the close signal. This seal-in action prevents re-closing on a
sustained close command as the close signal must be removed
to drop out the Y relay, and reestablish the close circuit, thereby
providing an anti-pump feature.
Circuit breaker mounted auxiliary switch contacts not used in
the control circuit are bought out for control and indication
functions. The metalclad equipment may provide a breaker
operated stationary auxiliary switch for additional contacts
(3, 6 or 10 stages are available.
SECT ON 7—Mechanical Checking and Slow Closing
7.1—Visual nspection
Visually inspect the circuit breaker for any signs of damage or
loose hardware.
7.2—Closing Spring Charging
Manually charge the breaker closing spring using the charging
handle provided (item 1, Figure 4). The closing spring is charged
by a ratcheting mechanism that advances by one ratchet tooth
at a time. When the spring is fully charged and the spring load is
held by the closing latch, the spring indicator (item 3, Figure 1)
will change from “DISCHGD” to “CHARG D”, and a positive snap
will be heard as the spring travels over center.
CAUTION: AFT R TH SPRING IS COMPL T LY CHARG D,
AS INDICAT D IN FIGUR 4, FURTH R FORCING CHARGING
HANDL MAY CAUS DAMAG TO TH CLOSING LATCH AND
ITS ASSOCIAT D PARTS.
1. Manual charging handle
2. Close spring gag hole
(Shown in closed position)
3. Spring charge indication
1
3
2
Figure 4 Manual charging

10
1 -- Closing spring gag plate
2 -- Manual charging lever
7.3—Closing Spring Gag
Insert the closing spring gag plate (item1, Figure 5) by opening
the closing spring gag hole cover and inserting the tip of the gag
plate between the end of the spring and the spring guide and
engaging the détentes on the gag plate into the slots in the
closing spring guide. Note that when the closing spring guide is
charged for gagging, an interference angle is exposed on the
left side of the breaker (item 3, Figure 19). With the closing
spring in the gagged position, this angle will provide
interference preventing use of the lift truck and racking of the
breaker element. No attempt should be
made to alter, modify or otherwise make inoperative this safety
feature. With the gag plate in position, depress the manual
close button. This action will partially discharge the closing
spring and also partially close the vacuum interrupter contacts.
Do not energize the secondary control circuit at this time.
7.4—Slow Closing
To manually slow close the breaker contacts, install the closing
spring gag, as described above, and push the manual close
button (item 11, Figure 3).
CAUTION: FAILUR TO PUSH TH CLOS BUTTON B FOR
CONTINUING TH SLOW CLOS PROC DUR WILL CAUS
DAMAG TO TH M CHANISM.
After pushing the manual closing button, put the manual charge
handle on the manual charge lever and move the handle up and
down. The breaker will be fully closed when the spring charge
indicator shows “CHARG D”.
CAUTION: WITH TH GAG PLAT INSTALL D, TH BR AK R
CLOS D, AND OP NING SPRINGS CHARG D, TH BR AK R
CAN B TRIPP D AT FULL SP D.
7.5—Gag Plate Removal
To remove the gag plate, the closing spring must be fully
charged. If the spring charge indicator does not show
“CHARG D” in the window, manually charge the spring until
it does. Lift up and push in on the gag plate to clear the
détentes on the gag plate from the slots in the closing spring
guide. While holding the gag plate up, remove it from the
opening. Close the gag hole cover. For safety, first close the
breaker by depressing the manual “CLOS ” button and then
depress the manual “TRIP” button. All stored energy is now
removed from the breaker.
Figure 6 Operating rod a embly
1. Wipe spring 5. Lock washer 9. Clamp screws
2. Wipe indicator (ML 18 only) 6. Hexagon projection 10. Interrupter movable contact rod
3. rosion disk 7. Operating rod insulator 11. Reference arm
4. Lock nut 8. Coupling clamp
Figure 5 Gag plate
10
11
9
8
7
6
5
4
3
2
1
2
1

11
SECT ON 8—Dimensional Checks
With the breaker closed and the gag plate installed, perform
the following dimensional checks.
8.1—Primary Contact Erosion
In the closed position, the erosion disk (item 3, Figure 6)
below the operating rod insulator is aligned with a reference
arm (item11, Figure 6) on new interrupters. As contact
erosion occurs, the erosion disk will move upward from
alignment with that reference arm. When erosion reaches 1/8
inch, the PowerVac® interrupters should be replaced. DO NOT
R -ADJUST TH ALIGNM NT OF TH ROSION INDICATOR
ARM XC PT WH N INSTALLING A N W VACUUM
INT RRUPT R.
8.2—ML-18 Wipe Spring Compression
With the breaker closed and the closing spring gagged,
measure with a feeler gauge and record the distance
between the top of the wipe indicator and the bottom of the
erosion disk for each phase (see Figure 27, Dimension W).
Trip the breaker with the closing spring gag plate still installed
and measure and record the distance between the wipe
indicator and erosion disk. Subtract the closed position
measurement from the open position measurement. The
result is the amount of wipe on each individual pole. The wipe
is to be greater than 0.075 inch. Adjustment is not required
until wipe is 0.075 inch or less. If adjustment is required see
WIP ADJUSTM NT in M CHANICAL ADJUSTM NT section.
The ML-18 and ML-18H mechanisms are furnished with very
low gradient wipe springs so that adjustment is not a
precision operation and considerable loss of wipe can be
tolerated without affecting performance.
8.3—ML-18H Wipe Spring Compression
With the breaker closed and the closing spring gagged,
Figure 7 Contact gap
measure with a feeler gauge and record the distance
between the bellville washer and the trunion between the bell
crank arms.
8.4—Contact Gap
The method of measuring the contact gap is as follows: With
the breaker in the open position, the closing springs charged,
and the closing spring gag plate installed, apply a piece of
masking tape to the surface of the operating rod insulator as
shown in Figure 7. Using a reference block, make a mark on
the tape near the top on all three poles. It is also advisable to
put a reference mark on the tape to identify to which pole the
tape is applied. Remove the closing spring gag plate and
close the breaker. Using the same procedure as above, re-
mark the tape. This new mark will be near the bottom of the
tape. Trip the breaker, remove the tapes and re-apply them to
a flat surface. Measure the distance between the two lines.
A caliper will give an accurate reading of the contact gap,
Dimension G: The gaps must be between the 0.60 inch
maximum at the center pole and 0.54 inch minimum at the
outer poles. It is not necessary that all readings correspond. A
properly adjusted breaker will have more gap and wipe on the
center pole than on the outside poles.
8.5—Coil Plunger Gap
The close coil and trip coil plunger gap dimensional checks are
made in the operating mechanism which is accessible from
the bottom. To accommodate these checks, the breaker
should be turned on its right side resting on two-by-four wood
blocks. DO NOT use the portable breaker lift truck.
CAUTION: DO NOT R ST UPON OR ALLOW ANYTHING TO
COM IN CONTACT WITH TH CLOSING SPRING
DISCHARG ROLL R (item 4,Fig. 20) ON TH RIGHT SID
OF TH M CHANISM.
1. 2X4 wood block
Figure 8 Breaker turned on right ide
1

12
8.5.1—Close Coil Plunger Gap
The close coil plunger gap and correct setting is shown in
Figure 9. The operation check and adjustment procedure for
the coil plunger will start with the close spring discharged,
and verification that the plunger moves freely over its full
stroke inside the coil. To check the closing coil plunger gap
the breaker should be open and the closing spring charged
and gagged. The measurement is made by first depressing
the close plunger button until resistance is felt, this accounts
for the free travel of the armature. The gap “T” measurement
is best made using a ‘go/no-go’ gauge. Refer to figure 9 for
gauge details. With the armature depressed until resistance is
felt the ‘go’ gauge must fit between the coil housing and the
surface of the black PVC cap covering the steel plunger base.
With the armature in the same position the ‘no-go’ gauge
must not fit between the coil housing and the plunger base.
The adjusting nut shown in Figure 9 is used to change this
measurement.
ML-18 Breakers with type designation
-0, -1 & -2 T= 0.25” to 0.30”
ML-18 Breakers with type designation
-3. T= 0.35” to 0.40”
ML-18H Breakers with type designation
-0. T= 0.35” to 0.40”
Figure 9 Clo e coil plunger gap
8.5.2—Trip Coil Plunger Gap
The trip coils #1 and #2 plunger gap and correct setting is
shown in Figure 10. The operation check and adjustment
procedure for the coil plunger will start with the breaker in the
open position and the closing spring in the charged condition
and verification that the plunger moves freely over its full
stroke inside the coil. This verification is also required for the
second trip coil when supplied. To check the trip coil plunger
gap the breaker must be closed with the closing spring
discharged. The measurement is made by first depressing
the trip plunger button until resistance is felt, this accounts for
the free travel of the armature. The gap ‘T’ measurement is
best made using a ‘go/no-go’ gauge with the ‘go’ end having
a thickness of .200 inches and the ‘no-go’ end with a
thickness of .251 inches. With the armature depress until
resistance is felt the “go” gauge must fit between the coil
housing and the surface of the red PVC cap covering the steel
plunger base. With the armature in the same position the “no-
go” gauge must not fit between the coil housing and the
plunger base. The adjusting nut shown in Figure 10 is used to
change this measurement. The same procedure is used for
measurement and adjustment of trip coil #2.
Plunger Gap T =. 250+.000/-.050
Figure 10 Trip coil plunger gap
8.6—Control Switch Adjustment
Adjustment of various control switches is done as follows.
8.6.1 LCS and SM/LS Switch Adjustment
The breaker is to be in the open position with the opening and
closing spring discharged. This results in the control switch
plungers being in the depressed position. The switches to be
checked are shown in Figure 11. On the LCS and the SM/LS
&CHG switch, the plunger rod is to be flush or slightly
recessed (1/32”) within the rear of switch body. This is a
visual check.
8.6.2 CL/MS Switch Adjustment
The adjustment of the CL/MS on ML-18 models with type-3
designations and ML-18H models with Type-0 designation is
set at the factory and no adjustment is required. Replacement
of the CL/MS switch or removal of the angle mounting
bracket will require re-adjustment of this switch for correct
operation of breaker’s track interlock and close latch. The
adjustment will insure that the switch contacts will not close
before the close latch is in its re-set position. To achieve this
condition shims are required between the CL/MS switch
housing and the plunger spacer. Insert shims until the CL/MS
contacts do not close when the close latch is in the reset
position. Then remove .005inch shim to allow the switch
contacts to close just as the close latch reaches the re-set
position. This will provide the proper timing between the
CL/MS switch and the close latch.
The adjustment of the CL/MS on ML-18 models with type –0,
-1 and -2 designations is set at the factory. Should adjustment

13
be required, adjust the wiring terminals and set the plunger
dimension from .99 to 1.01 from its mounting bracket as
shown in Fig.11.
8.6.3 L/MS Switch adjustment
The nut should be adjusted to fully extend the plunger.
AUX L ARY
SW TCH
STACK SW TCH
NEGAT VE
NTERLOCK
BAR
L/MS SW TCH
SH M PLACEMENT
CLMS SW TCH
ML 18 TYPE –0, -1, & -2
CLMS SW TCH
ML 18 TYPE –3
ML 18 H TYPE -0
Figure 11 Control Switche
LCS SW TCH

14
SECT ON 9—Electrical Checks
lectrical checking consists of electrical breaker operation
primary and secondary wiring high-potential testing (if
required), primary circuit resistance (if required), PowerVac®
interrupter high-potential testing, and insulation resistance to
ground.
9.1—Electrical Operation
To check the electrical operation, attach a secondary test
coupler to the circuit breaker connector. Check the control
voltage on the nameplate and close and open the breaker
several times.
CAUTION: R P AT D OP RATIONS AT A RAT XC D-
ING TWO P R MINUT MAY CAUS CHARGING MOTOR
OV RH ATING AND FAILUR .
Leave the circuit breaker in an open and spring discharged
condition after checks are complete and refer to metalclad
instruction book G K-39672 before inserting the circuit
breaker into a metalclad unit. Reinstall the front cover if it
has been removed.
9.2—High-Potential Test
If high potential tests to check the integrity of the primary
insulation is required, the AC high potential test described
below is strongly recommended. DC high potential testing is
not recommended. The following procedure must be adhered
to.
CAUTION: IF DC HIGH POT NTIAL T STING IS R QUIR D,
TH DC HIGH POT NTIAL MACHIN MUST NOT PRODUC
P AK VOLTAG S XC DING 50 kV.
NOTE: Always recheck with an AC tester if initial results are
questionable.
9.2.1 Primary Circuit
The breaker should be hipotted with the breaker closed.
An AC hipot machine capable of producing the test voltages
shown below may be used to hipot the breaker phase to
phase and phase to ground.
BREAKER VOLTAGE AC TEST VOLTAGE
4.16 KV 14 KV
7.2 KV 27 KV
13.8 KV 27 KV
The machine should be connected with its output potential at
zero and the voltage increased at 500 volts per second to the
test voltage and that voltage maintained for 60 seconds. The
voltage should then be returned to zero and the test leads
removed from the circuit and the breaker discharged to ground.
NOTE: Do not exceed the test voltage indicated for the
applicable breaker voltage rating. If the test should experience
a failure, STOP, turn off the test set and discharge the breaker
circuit.
1. Check the test set up and leads for connection errors.
2. Wipe down the breaker to remove any moisture, dust and
contamination.
3. Retest the breaker at the proper test voltage.
9.2.2 Secondary Circuit
Prior to hipotting the breaker secondary circuit, disconnect
the motor leads and thread a wire connecting all secondary
disconnect pins, except #24, the ground pin. Connect the
hipot machine from this wire to ground. Increase the voltage
to 1125 volts (rms) 60 Hz and maintain for 60 seconds.
Reduce the voltage to zero and remove the hipot machine
from the circuit. Remove the wire connecting the secondary
disconnect pins and reconnect the motor leads.
9.3—Primary Circuit Resistance
A resistance check of the primary circuit may be made
with the breaker closed. Use a low resistance measuring
instrument rated 100 amperes which measures in microhms.
The 100 ampere reading should be 30 to 60 microhms for a
1200 amp. Breaker, 25 to 50 for a 2000 ampere breaker. and
5 to 25 microhms for a 3000 ampere breaker when connected
across the primary bars on the breaker side of the disconnect
fingers. Do not connect directly to the disconnect fingers as
errors may occur due to finger spring pressure.
9.4—Vacuum nterrupter ntegrity Test
NOTE: Use of a DC hipot is not recommended, but can be
used for quick field checks only. DC testers frequently yield
false negative test results due to the capacitive component of
the vacuum interrupter during DC testing. In addition, most
lightweight DC testers have a very low leakage current trip
setting. Always recheck with an AC tester if initial results are
questionable. Prior to performing any vacuum interrupter
integrity test, the outside (external surface) of the vacuum
interrupters should be wiped clean of any contaminates with a
non-linting cloth or industrial type wiper. This is critical: the
entire external surface is to be completely free of all dirt,
debris, dust, oil, etc.
CAUTION: X-RADIATION WILL B PRODUC D IF AN
ABNORMALLY HIGH VOLTAG IS APPLI D ACROSS A PAIR
OF L CTROD S IN A VACUUM. X-RADIATION WILL
INCR AS AS VOLTAG INCR AS S AND/OR AS CONTACT
S PARATION D CR AS S. ONLY T ST A CORR CTLY-
ADJUST D CIRCUIT BR AK R.
DURING A HIGH POT NTIAL OR A VACUUM INT GRITY
T ST, ANY X-RADIATION WHICH MAY B PRODUC D WILL
NOT B HAZARDOUS AT A DISTANC SAF FOR HIGH
POT NTIAL T STING, IF TH T ST IS CONDUCT D AT TH
R COMM ND D VOLTAG AND WITH TH NORMAL OP N
CIRCUIT BR AK R GAP.
DO NOT APPLY VOLTAG THAT IS HIGH R THAN TH
R COMM ND D VALU . DO NOT US CONTACT S PA-
RATION THAT IS L SS THAN TH R COMM ND D OP N-
POSITION BR AK R CONTACT GAP.
A vacuum integrity test of the interrupter is required to ensure
that no loss of vacuum has occurred. The vacuum integrity
test is performed using an AC hi-potential tester. This test of
the vacuum interrupter will determine its internal dielectric
condition and vacuum integrity. With the breaker open,

15
individually check each interrupter by connecting the hi-pot
machine “Hot” lead to the primary bus bar and the ground lead
to the load side bus bar. If the machine has a center point
ground, the connections can be made either way. Apply 36 kV
(rms) 60 Hz at 500 vps and hold for 10 seconds. If no
breakdown occurs, the interrupter is in acceptable condition.
After the high potential voltage is removed, discharge any
electrical charge that may be present through the internal
ground of the test machine or by a grounded cable to one of
the phase bus bars.
If a failure of a vacuum bottle should incur during the integrity
test, the test procedure should be reviewed and the pole
piece cleaned. G failure rate for vacuum bottles is 0.0007 per
field unit.
Note the voltage level at failure on the first test, and retest
the phase pole piece. If the pole piece passes test, the
vacuum bottle is acceptable - STOP
STOPSTOP
STOP. If the test fails again but
at a higher voltage level than was observed in the first test,
clean the pole piece and retest. If a failure of the integrity test
occurs a third time, consider the vacuum bottle to have lost
vacuum and replace the complete pole piece as described
under Repair of Interrupter Assembly.
CAUTION: MANY DC HIGH POT NTIAL MACHIN S AR
HALFWAV R CTIFI RS. THIS TYP OF HIPOT T ST R
MUST NOT
NOTNOT
NOT B US D TO T ST VACUUM INT RRUPT RS.
TH CAPACITANC OF TH POW RVAC BOTTL S IS V RY
LOW AND TH L AKAG IN TH R CTIFI R AND ITS DC
VOLTAG M ASURING QUIPM NT IS SUCH THAT TH
PULS FROM TH HALFWAV R CTIFI R MAY B IN TH
N IGHBORHOOD OF 120 kV WH N TH M T R IS
ACTUALLY R ADING 40 kV. IN THIS CAS , SOM P R-
F CTLY GOOD BOTTL S CAN SHOW A R LATIV LY HIGH
L AKAG CURR NT SINC IT IS TH P AK VOLTAG OF 120
kV THAT IS PRODUCING RRON OUS BOTTL L AKAG
CURR NT. IN ADDITION, ABNORMAL X-RADIATION WILL
B PRODUC D.
Although a AC hi-potential test is recommended for checking
the vacuum integrity, a DC hi-potential test can also be
conducted on the vacuum interrupter. If a DC Hi-potential test
set is to be used, test voltage should not exceed 50kV DC,
and should be applied for 10 seconds. Interrupters must be
cleaned as previously discussed. If failure occurs, reverse the
polarity and retest. If the interrupter passes the second test,
STOP. The interrupter is acceptable. If the interrupter fails the
second test, we recommend a final test with an AC Hi pot
before replacement.
No attempt should be made to try to compare the condition
of one vacuum interrupter with another nor to correlate the
condition of any interrupter to low values of dc leakage
current. There is no significant correlation. After the high
potential voltage is removed, discharge any electrical charge
that may be retained.
An acceptable AC high potential machine is available from: G
Company, Burlington, Iowa, Catalog Number 282A2610P001.
Acceptable AC high potential machines are:
Hipotronics Model 7BT 60A
Hipotronics Model 60HVT
James G. Biddle Catalog 222060
Phoenix Model 660-10P
Acceptable DC high potential machines are:
Hipotronics Model 860PL
Hipotronics Model 880PL
G /Programma VIDAR
9.5— nsulation Tests
The primary circuit insulation on the breaker may be checked
phase to phase and phase to ground using a 2500 Volt or
other suitable megohmeter.
Since definite limits cannot be given for satisfactory insulation
values, a record should be kept of the megohmeter readings
as well as temperature and humidity readings. This record
should be used to detect any weakening of the insulation
from one check period to the next. Generally, readings should
equal or exceed 10,000 megohms.
To measure the breaker secondary circuit insulation
resistance, disconnect the motor leads and thread a wire
connecting together all secondary disconnect pins except
#24, the ground pin. The measurement is made by
connecting a 500 Volt megohmeter from the wire to ground.

16
SECT ON 10—Checking and nstalling Breakers
CAUTION: IN THE DISCONNECTED/TEST POSITION IF TH
COMPARTM NT S CONDARY CON- TROL CIRCUITS AR
N RGIZ D, TH FOLLOWING PROC DUR MUST B
FOLLOW D TO PR V NT ARCING AND BURNING OF TH
MOTOR CIRCUIT PINS IN TH S CONDARY CONTACT
BLOCKS: ITH R CHARG TH CLOSING SPRING
MANUALLY, OR PUSH IN AND HOLD TH MANUAL CLOS
BUTTON TO OP N TH MOTOR CIRCUIT, TH N PULL
DOWN TH HANDL AND XT ND TH BR AK R
S CONDARY CONTROL CONTACT BLOCK TO FIRMLY
NGAG WITH ITS MATING S CONDARY CONTROL
CONTACT BLOCK IN TH COMPARTM NT. R L AS
CLOS BUTTON TO ACTIVAT SPRING CHARGING MOTOR.
CAUTION: IF CONTROL POW R IS AVAILABL , CLOS
TH CIRCUIT BR AK R USING TH CONTROL SWITCH ON
TH COMPARTM NT DOOR. THIS OP RATION WILL
CH CK TH ADJUSTM NT OF TH 52/LCS SWITCH. IF TH
BR AK R WILL NOT CLOS L CTRICALLY, R CH CK TH
52/LCS ADJUSTM NT. IF CONTROL POW R IS NOT AVAIL-
ABL , PUSH TH MANUAL CLOS BUTTON AND
R CHARG TH CLOSING SPRING MANUALLY. SPRING
CHARGING WILL OCCUR AUTOMATICALLY IF CONTROL
POW R IS CONN CT D.
Verify that spacing between the lower inside edges of the
breaker roller track in the metalclad compartment is 29.807”
min. to 29.857” max. Check that the breaker is OP N and that
the closing spring is DISCHARG D. Install the PowerVac®
circuit breaker into the DISCONN CT/T ST position in the
metalclad compartment.
NOTE: When inserting the breaker and prior to racking, the
operator must ensure that both the right and left side racking
arms are engaged on the drive blocks. Racking arms must be
fully engaged for breaker to rack in properly. Failure to do so
could result in jamming of the racking arms with the guide rail.
With the breaker in the CLOS D condition, attempt to install
the racking crank. The racking crank should be blocked by the
POSITIV INT RLOCK. Trip the breaker and install the racking
crank and rack the breaker toward the connected position.
During the first five turns, usually between the third and
fourth turns, the spring discharge interlock will discharge the
closing spring. The contacts of the circuit breaker should
remain open. (If adjustment is required see M CHANICAL
ADJUSTM NTS sections 16.7 and 16.8.) Rack the breaker
into the CONN CT D position and charge the closing spring.
If secondary control power is available the closing spring will
charge automatically. Assure that the breaker is in the OP N
condition.
Rack the breaker from the CONN CT D back to the
DISCONN CT position. During the first three turns, the spring
discharge interlock should discharge the closing spring and
the breaker contacts should remain OP N. (If adjustment is
required see M CHANICAL ADJUSTM NTS sections 16.7 and
16.8.)
With the breaker in the disconnect position and the closing
spring discharged, rack the breaker in 5-7 turns. With control
power on, plug in secondary disconnect. Spring charge motor
should not operate.

17
SECT ON 11—Maintenance
WARNING: B FOR ANY MAINT NANC WORK IS
P RFORM D, MAK C RTAIN THAT ALL CONTROL
CIRCUITS AR D - N RGIZ D AND THAT TH BR AK R IS
R MOV D FROM TH M TALCLAD UNIT. DO NOT WORK
ON TH BR AK R OR M CHANISM WHIL IT IS IN TH
CLOS D POSITION WITHOUT TAKING PR - CAUTIONS TO
PR V NT ACCID NTAL TRIPPING BY BLOCKING TH TRIP
LATCH. DO NOT WORK ON TH BR AK R WHIL TH
CLOSING SPRING IS CHARG D UNL SS IT IS S CUR D IN
THAT POSITION BY TH CLOSING-SPRING GAG.
11.1—General
PowerVac® circuit breakers have been designed to be as
maintenance-free as practicable. They include features such
as sealed vacuum interrupters and long-life synthetic greases
which contribute to many years of trouble-free performance
with a minimum amount of maintenance.
11.1.1 PowerVac® nterrupter
The PowerVac® interrupter used in this breaker is a reliable,
clean interrupting element. Since the contacts are contained
in a vacuum chamber, they remain clean and require no
maintenance at any time. The metallic vapors eroded from the
contact surfaces during high current interruption remain in the
chamber and are deposited on metal shields thus insuring a
high dielectric value of the vacuum and the walls of the
interrupter.
11.1.2 Trouble Reporting
Although all reputable manufacturers design their products to
perform satisfactorily with a minimum of problems, the I
Switchgear Committee, an organization of both users and
manufacturers, recognize the need for a common trouble
reporting format. A reproducible copy of this form is included
inside the rear cover of this book and is recommended for use
with any manufacturer’s circuit breakers.
The intent is for each maintenance organization to keep
specific problem files with this information documented.
If the problem is serious or repetitive, a summary should be
sent to the appropriate manufacturer for action. The level of
detail included on the form is considered very desirable so
that the manufacturer’s investigator may more thoroughly
understand and solve the reported problem.
11.2—Service Conditions
The frequency of required maintenance depends on
the severity of the service conditions of the switchgear
application. If the service conditions are mild, the interval
between maintenance operations may be extended to 10
years or 10,000 no load or 5,000 normal load switching
operations. Mild service conditions are defined as an
environment in which the switchgear is protected from the
deleterious effects of conditions such as:
Salt spray
Changes in temperature that produce condensation
Conductive and/or abrasive dust
Damaging chemicals and fumes
Vibration or mechanical shock
High relative humidity (90%)
Temperature extremes (below –30° C or above +40° C)
11.3—Fault nterruptions
The erosion rate of the primary contacts in the vacuum
interrupters is very low for normal load switching operations.
However, fault current interruptions at or near the breaker
rating may result in appreciable contact erosion. With frequent
fault interruptions it is necessary to perform maintenance
based on the number of interruptions. After 15 full fault
interruptions the following should be performed:
1. Contact erosion check.
2. Wipe and gap check
3. Vacuum interrupter integrity test.
11.4—Contact Erosion
Check in the breaker-closed condition per PRIMARY
CONTACT ROSION section 8.1. When erosion reaches
.125 inch, the interrupter should be replaced.
11.5—Transfer Finger Wear
With the breaker open, examine the moving contact rod
projecting below the transfer fingers (item 10, Figure 6).
Wipe off the lubricant in order to see the metal surface
condition. The finger locations should present a burnished
silver contact without copper appearance at more than one
location. If copper is visible at more than one location per pole
or the silver plating is torn, the interrupter assembly should be
replaced. Re-lubricate with 0282A2048P009.
11.6—Mechanism
Check all items covered in INSTALLATION and readjust or
tighten hardware as required. Lubricate as recommended
under LUBRICATION.
11.7—Primary nsulation Parts
Using dry, non-linting cloth or industrial-type wipers, clean
accessible insulation surfaces on the interrupter supports
and operating rod insulators. In service locations where
contamination is heavy or external flashovers, have occurred
during interrupter high-potential testing, remove the
interrupter assemblies per the procedure in R PAIR AND
R PLAC M NT and clean the inside surfaces of the
interrupter supports and the outer insulation surfaces of the
PowerVac® interrupters. Before beginning cleaning process
discharge the static charge on the interrupter with midband
ring(Fig 24). Removal and reassembly of interrupter
assemblies will normally not require adjustment due to the

18
design of the interrupter operating rod insulator connection.
They should be returned to the same location from which they
were removed.
11.8—Lubrication
Proper lubrication is important for maintaining reliable circuit
breaker performance. The ML-18 and ML-18H mechanisms
use bearings which have a synthetic lining in some locations.
These bearings do not require lubrication to maintain low
friction, but lubrication does not harm them and oiling lightly is
recommended. Sleeve bearings are used in some linkage
locations and needle or roller bearings are used for low friction
on trip shaft and close shaft.
Bearings are lubricated during factory assembly with grease
and oil, but all lubricants have a tendency to deteriorate with
age. Providing a fresh lubricant supply at periodic intervals is
essential to proper breaker operation, especially where
frequent operation may have forced lubricant out of the
bearing surfaces. Apply a few drops of light synthetic machine
oil such as Mobile 1 at each bearing. Apply a coat of
0282A2048P009 grease on the four corners of the closing
spring guide where it enters inside the spring.
Metal-to-metal contact surfaces should be cleaned and
lubricated with 0282A2048P009 grease to provide cleanliness
and prevent oxidation.
lectrical primary contact surfaces also require periodic
lubrication to inhibit oxidation and minimize friction. At each
inspection and maintenance interval, do the following:
1. Wipe clean and coat lightly with grease
(0282A2048P009) all silvered primary contact surfaces
such as the movable contact rod of the interrupter and
the primary disconnect fingers.
2. Clean and coat lightly with grease the pins of the
secondary disconnect coupler.
11.9—Recommended Maintenance
The following operations should be performed at each
maintenance check:
1. Perform a visual inspection of the breaker. Check for
loose or damaged parts.
2. Perform slow closing operation described under
M CHANICAL CH CKING AND SLOW CLOSING.
3. Check the erosion indicator and the wipe and gap as
described under DIM NSIONAL CH CKS.
4. Perform the vacuum interrupter integrity test as
described under L CTRICAL CH CKS.
5. Lubricate the breaker operating mechanism as described
under LUBRICATION.
6. Check the electrical operation using the test cabinet (if
available) or the test position in the metalclad switchgear.
CAUTION: R P AT D OP RATIONS AT A RAT XC DING
TWO P R MINUT MAY CAUS CHARGING MOTOR
OV RH ATING AND SUBS QU NT MOTOR FAILUR .
7. xamine the movable contact rod of the vacuum
interrupter. With the breaker open, wipe the lubricant off
the rod and examine the silver surface. The rod should
have a burnished appearance without copper appearing
through the silver. If copper is visible at more than one
location per pole, or if the silver plating is torn, the
interrupter assembly should be replaced. Re-lubricate
movable contact rod with 0282A2048P009 grease
8. If desired, perform the additional electrical tests (Megger,
Primary and Secondary High Potential, and Primary Circuit
Resistance). See L CTRICAL CH CKS.
Closing coil
current Tripping coil current Fuse size close CKT. Protection
Control
Voltage
Source
Closing
range
Tripping
Range
W/O
FBT
With
FBT
5 cycles 3 cycles
Motor
nrush
current
Motor
Windup
current W/O
FBT
With
FBT
48 VDC 38-56 28-56 13.7 - 17 17 34 17 30 -
125 VDC 100-140 70-140 6 35.7 5.9 10.5 23 8 20 30
250 VDC 200-280 140-280 2.4 12 4.7 10.8 18 3.8 15 20
120 VAC 104-127 295-360 VDC* 6 - 3.7 3.7 35 15 20 -
240 VAC 208-254 295-360 VDC* 2.4 - 3.7 3.7 20 6 20 30
*Capacitor trip, 120/240 VAC requires the capacitor trip to operate a 340 trip coil.
Tabl 1. Control D vic s and Voltag s

19
SECT ON 12—Timing
Timing and speed checks are optional and also depend on the
level of maintenance performed. Generally these tests are not
required for normal maintenance. If a new mechanism has
been installed or extensive repair, replacement or major
disassembly has been performed, it is recommended that
these tests be performed.
To determine contact velocity, a travel recorder and
oscillograph are required. Optional travel recorders can be
obtained through your local G Sales Office by ordering part
number 0144D1235G001. A typical travel trace and
interpretation are shown in Figure 12.
Timing may be checked by monitoring control circuit voltage
and using no more than six volts DC and one ampere through
the vacuum interrupter contact to indicate closed or open
condition. Typical time ranges vary with coil voltage, but
nominal values are:
Initiation of trip signal to contact parting
32-45 Milliseconds( 5 Cycle)
25-30 Milliseconds (3 Cycle)
2 Milliseconds maximum pole spread
Initiation of close signal to contact closing
35-75 Milliseconds
2 Milliseconds maximum pole spread
Trip-free operation maybe checked by applying a
simultaneous close and trip signal, and a minimum re-close
operation may be checked by tripping a charged breaker open
while maintaining a close signal.
Instantaneous re-close time* 85-150 Milliseconds.
*Time from application of trip signal until breaker contacts
re-close.
Figure 12 Sample operating peed graph

20
SECT ON 13—Opening and Closing Speed
The opening speed is modified by moving the opening spring
adjusting nut on the opening spring assemblies. A change in
opening speed affects the closing speed. Reference Figure 13.
NOTE: Tightening of the opening spring adjusting nut will
decrease the closing time and speed while increasing opening
time and speeds. Loosening will have a reverse effect.
The operating speeds are as follows:
Operation
OperationOperation
Operation Feet Per Second
Feet Per SecondFeet Per Second
Feet Per Second
Open 5.0 nominal, 4.5 minimum
Close 3.5 nominal, 4.0 maximum
V.I. STOP CENTER PHASE
Figure 13 Contact gap adju tment