ETI PI-5000 User manual

PRIMARY INJECTION CIRCUIT BREAKER
TEST SET
INSTRUCTION MANUAL
Models
PI-2500 and PI-5000
Electrical Test Instruments, LLC.
8430 Spires Way, Suite A-F
Fredrick, MD 21701
www.ETIPrecision.com
[phone]
Fax [phone]

Electrical Test Instruments PI-2500 and PI-5000
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Copyright (C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
TABLE OF CONTENTS
SECTION I: GENERAL INFORMATION and SPECIFICATIONS
WARNING I-1
Introduction I-2
General Description I-2
Monitor and Controller MAC-20 I-5
Proposed Enhancements I-5
Advantages Compared to Other Test Sets I-6
Trademarks I-6
PI2500 Specifications I-7
PI5000 Specifications I-7
MAC-20 Specifications I-8
SECTION II: DETAILED DESCRIPTION
Theory of Operation
High Current Test Sets II-1
PI-2500 Main Circuitry II-1
PI-2500 Control Circuitry II-1
AUX-5000 Main Circuitry II-1
AUX-5000 Control Circuitry II-1
PI-2500 Indicator Control Panel Circuitry II-4
MAC-20 Monitor Controller Circuitry II-4
MAC-20 Software II-5
Major Parts Identification and Operation
MAC-20 Control Panel II-6
MAC-20 Internal Parts II-9
Figure II-1: Front Panel II-10
Indicator Control Panel II-11
Figure II-2: Retrofit Indicator Panel II-12
SECTION III: MAC-21 Monitor and Controller
MAC-21 Specifications III-1
MAC-21 Unit Circuitry III-2
MAC-21 Software III-2
MAC-21 Parts Identification and Operation III-4
MAC-21 Internal Parts III-8
Figure II-1: Front Panel III-9
Maintenance and Calibration of MAC-21 III-10
Parts List (MAC-21) III-12
Overall Schematic (MAC-21) III-13

Electrical Test Instruments PI-2500 and PI-5000
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Copyright (C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
SECTION IV: OPERATING INSTRUCTIONS
Pre-Test Installation and Setup IV-1
Basic Guidelines and Suggestions IV-3
Single Pole Molded Case Breakers IV-4
Multi-pole Molded Case Breakers IV-7
Low Voltage Power Breakers IV-10
Motor Overload Relays IV-14
Ratioing Current Transformers IV-16
SECTION V: SERVICE INFORMATION AND DOCUMENTATION
Maintenance and Calibration of PI-4000B V-1
Maintenance and Calibration of MAC-20 V-1
Parts List (PI-2500) V-4
Parts List (AUXI-5000) V-4
Parts List (Indicator Control Panel) V-5
Parts List (MAC-20) V-6
Overall Schematic (PI-2500) V-7
Overall Schematic (AUX-5000) V-7
Overall Schematic (Indicator Control Panel) V-8
Overall Schematic (MAC-20) V-9
Warranty END
Additional Schematics END

Electrical Test Instruments PI-2500 and PI-5000
Section II –Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
SECTION I
GENERAL INFORMATION

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-1
SECTION I
GENERAL INFORMATION
WARNING
WARNING - READ THIS ENTIRE MANUAL AND
THOROUGHLY FAMILIARIZE YOURSELF WITH THE UNIT
OPERATION PRIOR TO CONNECTING THE UNIT TO A
SOURCE OF POWER. HIGH CURRENT TEST SETS ARE
NORMALLY POWERED FROM HIGH CAPACITY 208 VOLT TO
575 VOLT SERVICES, AND IMPROPER CONNECTION OR
OPERATION COULD CAUSE DAMAGE TO THE TEST SET AND
EQUIPMENT UNDER TEST, AS WELL AS CREATE AN UNSAFE
CONDITION FOR PERSONS OPERATING THE SET.

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-2
INTRODUCTION
A primary injection test set such as the PI-2500 and PI-5000 is a device with
high current, low voltage AC outputs for testing direct acting low voltage circuit
breakers. Current is injected through the main contacts of the breaker to simu-
late actual fault conditions, which tests the operation of CTs, solid state, thermal,
or electromechanical trip devices, and the actual trip mechanisms and breaker
contacts.
GENERAL DESCRIPTION –PI2500
The PI-2500 is a versatile and technologically advanced primary injection test
set capable of testing circuit breakers up to 2000 amperes frame size. It incor-
porates an improved low impedance output transformer with dual primaries to
facilitate its use on power sources of 480 VAC as well as 240 and 208 VAC, and
dual secondaries to provide optimal impedance matching to a wide range of
breaker sizes. High capacity internal fan cooling allows maximum utilization of
the output transformer and faster recovery after overload conditions.
It is housed in a rugged aluminum frame enclosure with removable sides and
top for easy access to internal components. The sides are clear of protruding
components, and a full-width handle facilitates moving the unit. Locking pneu-
matic swivel castors on one end provide ease of mobility and allow the test set
to be moved on rough surfaces.
The indicator control panel and MAC-20 are mounted in a compact hood on the
top, which provides protection during transportation. A flat area on the top sur-
face can be used for convenient placement of manuals, breaker curve books,
and auxiliary instruments. The auxiliary 120 VAC GFI protected outlet is conven-
iently located on the rear of the unit and protected by a 4-ampere circuit
breaker.
The output stab connectors are slotted to accommodate special breaker stab
adaptor plates as well as being able to connect to the AUX-5000 for increased
output capacity. The rugged silver-plated copper stab adaptors supplied with
the test set are designed to be used for both vertical and horizontal stabs and
have both ½” and ¾” output plates. Standard ½”-13 stainless steel hex head
bolts with matching nuts and washers are used to connect the output stab
plates, and they may be replaced easily.
A series adaptor bar allows the output to be configured for continuous current
of 1000 amps at 15 VAC for testing breakers that require connection via cables.
A configuration switch on the output faceplate adjusts the internal CT output
for proper readings in either configuration.

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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The test set may be plugged into any 60 Hz AC voltage source of 200-250 VAC
or 400-500 VAC, and will work on 50 Hz sources of 200-210 VAC or 400-420 VAC.
The line voltage is displayed on the indicator control panel digital meter. An in-
put selector switch can be set for 208, 240, or 480 VAC inputs. An internal volt-
age sensor automatically ensures that the switch is set correctly before AC con-
trol power can be turned on, and monitors input voltage for compliance to spec-
ifications.
The Vernier uses a large wheel to adjust the output manually within the range
determined by the coarse tap, as well as a motorized control actuated by means
of a smart control switch. When the switch is pressed briefly, the Vernier moves
in a very small increment for fine control. When the switch is held, the Vernier
moves very quickly, so that the entire span may be traversed in less than five
seconds. The approximate Vernier position is displayed on an LED indicator bar
graph. For the PI-2500, the Vernier is always turned clockwise to increase out-
put.
The electronically controlled tap selection uses power contactors to set the
coarse tap. The unit powers up in the lowest tap position (1), and the setting may
be adjusted by means of a rocker switch on the indicator/control panel. If the
switch is held, the taps change at a rate of about two seconds per tap. Tap
change is not allowed when output is on. Note: Output taps 1-3 only for the PI-
2500. Output taps 4-9 are only operational when the AUX-5000 section is con-
nected to the PI-2500 section.
The indicator/control panel features two temperature indicators: one for the
output bus temperature, and the other for the overall system temperature. This
is determined by a combination of actual winding temperature, and a “virtual
temperature” which is derived from time and current duty cycle usage as mon-
itored by a “POD”, or Programmable Overload Device. Additional details are
available in a separate manual. If either temperature exceeds a safe operating
level, the interlock is asserted, and the output section is de-energized. Addi-
tional thermostatic sensors in the output transformer windings will also assert
the interlock if unsafe temperature levels are detected.
The output voltage of the test set is provided on the indicator/control panel for
monitoring by means of a separate digital voltmeter.
Primary catastrophic overload protection for the test set is accomplished with
input fuses having high interrupting current capacity. Overload of the output
system is sensed by means of the previously mentioned “POD” on the Vernier
autotransformer, and thermal sensors in the transformer winding. Thermal
switches are also installed in the transformer windings. The combination of
these devices allows full utilization of the overload capability of the test set and
eliminates costly and cumbersome fuse replacement required in other test sets.

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
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The output of the test set is controlled by means of a proven SCR controller,
which drives modular solid-state relays. This provides precise initial phase angle
control to reduce DC offset for inductive loads and more consistent pulse cur-
rents. Snubbers are incorporated to eliminate false firing and latching problems.
The phase angle is internally adjustable and is preset for optimal waveforms
with most breakers.
The measurement of output current and time is accomplished by means of the
proven MAC-20, which uses highly accurate A/D circuitry and intelligent firm-
ware to resolve true-RMS values of distorted waveforms. It also provides features
such as preset ON times for convenient jogging of output current without over-
heating the breaker or causing unwanted trips.
The entire test set has been designed for reliability, ruggedness, and ease of use.
Sophisticated electronics in the indicator/control panel and the MAC-20 provide
state of the art accuracy and convenience, while simple connections allow for
easy removal and replacement for transportation or service. All covers are re-
movable, allowing easy access to all internal components. An internal relay
panel located just under the top panel contains most of the circuitry, facilitating
service and maintenance. The rear panel may be removed for access to input
fuses, control fuses, and the SCR board. A large bottom-mounted fan provides
airflow to the transformer and output bus. The cabinet is designed with no pro-
truding components on the sides, so it can be navigated through narrow door-
ways without problems. The input jacks and voltage switch are protected by
being mounted on a recessed rear panel.
The reduced length and width of the test set allows it to be maneuvered in tight
spaces and it can be lowered into a shaft 26” x 30”, or a manhole 40” diameter.
Provisions have been made on the bottom of the frame for a lifting sling to be
attached without slipping from the corners.
GENERAL DESCRIPTION –PI5000
The PI-5000 is composed of the PI2500 as described above, and the AUX-5000
auxiliary output unit, which when combined gives the unit the capability of
testing 4000 ampere breakers, with essentially the same specifications as the
proven PI-4000B. The auxiliary unit is smaller than the PI2500, so it can also be
maneuvered easily in tight spaces or lowered into shafts and manholes that
would not be possible with a larger single piece unit.
The AUX-5000 is easily attached to the PI-2500 by means of horizontal bus
bars with stainless steel socket head cap bolts and sturdy nutplates. The AUX-
5000 is simply rolled into place to mate with the PI-2500, and then the cap
screws are tightened. It is recommended to use a stubby fine pitch ratchet
wrench or a pneumatic air ratchet, with an Allen wrench hex bit.

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
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The main electrical power and ground connections to the AUX-5000 are the
same twist-lock connectors as those on the PI-2500. Power cables stored in a
compartment in the AUX-5000 are then connected to the PI-2500. The con-
nectors are color-coded and must be connected with black to black and red to
red.
There is also a control cable which connects from the AUX-5000 to the PI-
2500.
The output of the AUX-5000 is identical to that of the PI-4000B, and accom-
modates standard breaker stabs, for continuous output of 4000 amperes. It
can also be configured in series mode for a continuous output of 2000 am-
peres. The configuration switch on the PI2500 must be set to 4000 or 2000 for
proper output readings.
The combined unit, known as the PI-5000, can only be used on 480 VAC.

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
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MONITOR AND CONTROLLER MAC-20
The MAC-20 microprocessor-based measurement and control unit features
digital readout of current and time enhanced by digital signal processing.
Pulse (memory) mode provides fast and accurate automatic evaluation of out-
put current pulses as short as one-half cycle.
The MAC-20 incorporates a precision A/D converter and special firmware for
true-RMS continuous and pulse current reading with much greater accuracy.
It also utilizes a sophisticated current sensing system for more reliable current
latch mode operation and better timing accuracy. An LED digital readout for
current in four ranges from 1000 A to 100 KA reduces the chance of operator
error.
An integral auto ranging timer with LED readout provides four digits in sec-
onds or cycles mode, with a resolution of 0.001 second or 0.5 cycle. A preset
function allows you to set a maximum ON time in seconds or cycles, for con-
venient "jogging" of output to desired current or setting time for heat runs and
long-time tests.
A current hold feature is also built in. When the desired current is displayed, a
simple touch of the MAINTAIN key activates the function, which automatically
adjusts the motorized Vernier to hold the current within 5 amperes.
The memory current displayed after a test indicates the true RMS value of the
entire pulse, no matter how long or short it was, except for instantaneous trip,
where the peak RMS value is used. After a test, it is possible to read the peak
RMS value, which indicates the amount of DC offset or distortion, or the last
displayed average RMS reading, which is useful for pickup testing.
The entire metering and control package are designed to be removed and re-
placed very easily, so that it may be transported separately.
A remote-control accessory is available which allows the Vernier to be oper-
ated by means of a small hand-held control, which also allows the test set to
be initiated.

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-7
PI-2500 SPECIFICATIONS
INPUT SUPPLY:
208/240 or 480 VAC +/- 10% (Field switchable)
SINGLE PHASE
60 HZ (50 Hz at 10% lower line voltages)
15 KVA (Continuous) at 12 KVA output (80% efficiency)
OUTPUT CURRENT & OVERLOAD CAPABILITIES:
7.6V (Par)
15.2 V (Ser)
Ovld
Duty
Max ON Time
Min OFF
Time
Max Inp Curr
(@480/240)
2000 A
1000 A
1x
100%
CONTINUOU
S
N/A
32 / 64
2800 A
1400 A
1.4x
50%
15 Minutes
15 Minutes
45 / 90
4000 A
2000 A
2x
25%
5 Minutes
15 Minutes
64 / 128
6000 A
3000 A
3x
10%
1.5 Minutes
15 Minutes
96 / 192
8000 A
4000 A
4x
6%
45 Seconds
15 Minutes
128 / 256
10000 A
5000 A
5x
4%
4 Seconds
2 Minutes
160 / 320
14000 A*
7000 A*
7x
2%
1 Second
2 Minutes
224 / (448 *)
20000 A*
10000 A*
10x
1%
0.2 Second
2 Minutes
320 / (640 *)
*Available with 480 VAC input only; Max ON Times may be less at 208 or 240 VAC
DIMENSIONS AND NET WEIGHT
Height: 41 in. (1041 mm) (includes castors and hood)
Width: 29.0in. (737 mm)
Depth: 25.0 in. (635 mm)
Weight: 515 lb. (192 kg)
STANDARD ACCESSORIES
Stabs, BS-50HV (½” bus, horizontal or vertical) 1 set
Stabs, BS-75HV (¾” bus, horizontal or vertical) 1 set
Stab adaptor assembly 1 pair
Series bars 3 pcs
Input power plugs 3 pcs
Contacts leads 1 pair
Technical manual 1 copy
OPTIONAL ACCESSORIES
Remote initiate cable
Serial Interface Cable

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-8
PI-5000 SPECIFICATIONS
INPUT SUPPLY:
480 VAC +/- 10%
SINGLE PHASE
60 HZ (50 Hz at 10% lower line voltages)
45 KVA (Continuous) at 36 KVA output (80% efficiency)
OUTPUT CURRENT & OVERLOAD CAPABILITIES:
7.6V (Par)
15.2 V (Ser)
Ovld
Duty
Max ON Time *
Min OFF Time
Max Inp Curr (@480
4000 A
2000 A
1x
100%
CONTINUOUS
N/A
96
5600 A
2800 A
1.4x
50%
15 Minutes
15 Minutes
134
8000 A
4000 A
2x
25%
5 Minutes
15 Minutes
192
12000 A
6000 A
3x
10%
1.5 Minutes
15 Minutes
288
16000 A
8000 A
4x
6%
45 Seconds
15 Minutes
384
20000 A
10000 A
5x
4%
4 Seconds
2 Minutes
480
28000 A
14000 A
7x
2%
1 Second
2 Minutes
672
40000 A
20000 A
10x
1%
0.2 Second
2 Minutes
960
DIMENSIONS AND NET WEIGHT PI-5000 AUX
Height: 35 in. (889 mm) (includes castors)
Width: 30.0 in. (762 mm)
Depth: 25.0 in. (635 mm)
Weight: 585 lb. (218kg)
DIMENSIONS AND NET WEIGHT PI-5000 (Combined PI-2500 & PI-5000AUX)
Height: 41 in. (1041 mm) (includes castors and hood)
Width: 48.0 in. (1219 mm)
Depth: 25.0 in. (610 mm)
Weight: 1100 lb. (411kg)
STANDARD ACCESSORIES
Stabs, BS-50HV (½” bus, horizontal or vertical) 1 set
Stabs, BS-75HV (¾” bus, horizontal or vertical) 1 set
Input power plugs 1 pair
Contacts leads 1 pair
Technical manual 1 copy
Remote initiate cable 1 each
OPTIONAL ACCESSORIES
Series bar
Serial Interface Cable

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-9
SECTION II
DETAILED DESCRIPTION

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-10
SECTION II
DETAILED DESCRIPTION
THEORY OF OPERATION
High Current Test Sets
High current test sets generally consist of the following:
1. One or more coarse taps accomplished by:
(a) A tapped autotransformer providing several equal steps of volt-
age or
(b) A multi-section output transformer
2. A continuously variable Vernier adjustment between coarse taps by
means of:
(a) A variable autotransformer and boost transformer, or
(b) A variable autotransformer connected to a section of the out-
put transformer.
3. An output transformer with one or more isolated low voltage, high
current secondary.
4. Power control circuitry consisting of switches, relays, protective de-
vices, etc.
5. Current measurement circuitry consisting of sensors, current meter,
and timer.
In general, a primary voltage is selected by means of a combination of coarse
tap and Vernier adjustment. This voltage is stepped down by the output trans-
former to provide the desired current into the load impedance.
PI-2500 Main Unit Circuitry
Main power is applied to the PI-2500 by means of standard high current plug
and socket connectors, which are supplied for the customer to connect to the
power source with appropriate flexible leads. A ground connector is also pro-
vided for a solid ground connection.
Primary protection is provided by high capacity 100 ampere input fuses (F1 and
F2). After that, the control section is protected by smaller 5 ampere fuses (F3 and
F4), and the power section is isolated by means of high current contactors (K1
and K2).
Transformer T6, protected by fuse F6, steps down the primary voltage by a factor
of ½, and is connected to a wide range switching power supply in the indicator

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Page II-11
control panel to provide 12 VDC. The dual primary of transformer T6 steps it
down by a factor of 1/2, and T10 steps it down by another factor of ½, and this
voltage is sensed by a voltage relay circuit and read on the control panel LED
meter. When the primary voltage is between about 200 and 270 VAC, this circuit
allows operation in 208 or 240 VAC mode. If the voltage is between about 420
and 520 VAC, operation is allowed in 480 VAC mode. Control power cannot be
turned on if the voltage is outside these bounds.
When AC power is supplied to the test set, the 24 VDC power supply PS1 is pow-
ered through the stepped down primary winding of T6, and will operate from
supply voltages of 500 to 190 VAC. This DC control voltage is used for all of the
tap contactors. There is a current limiting circuit which is required to keep the
output of the power supply from shutting down while charging the large ca-
pacitors that are needed to pull in the contactors.
Another transformer, T9, supplies nominal 104, 120 or 240 VAC power to the con-
trol panel, which has an internal 12 VDC power supply which powers other por-
tions of the control circuitry of the control PCB.
When the input voltage selector switch S1 is the 208 or 240 V position, relay K6
is energized, setting the primary windings of transformer T4 in parallel. This also
energizes relay K1 on the voltage sensor PCB and provides an interlock and in-
put selector error indication. The voltage sensor PCB rapidly flashes the Input
Select Error LED on the control panel for 5 seconds during startup, and then
turns off if input voltage is within bounds as determined by the input selector
switch position. If line voltage is incorrect, the Input Select Error LED will flash,
and control power cannot be turned on. If control power is energized, brief volt-
age sags or surges will flash the LED as a warning. If such voltage excursions
persist for longer than about 0.2 seconds, the control power will drop out.
Binding post BP1 is provided for separate connection to an earth ground, to
check for ground integrity. When there is continuity from this point to chassis
ground, a relay on the control PCB is energized, and enables the interlock for
control power. If ground integrity is not sensed, the Ground Open LED DS1 will
light. A separate lead should be connected to the external equipment ground
system to verify that the main grounding cable is intact. Do not defeat this
safety feature by jumpering the ground binding post to the test set frame.
When the control power switch in the indicator control panel is pressed, and all
voltage interlocks are OK, relay K7 is energized, which provides 120 VAC control
power to the auxiliary GFI outlet, protected by 4 ampere circuit breaker CB1. A
relay on the control PCB provides 120 VAC control power to the entire test set,
including the fans and the main contactors. In 208 V input mode, the control
voltage is boosted by transformer T7.
If all power interlocks are OK, the Main Power switch in the indicator control
panel may be pressed to activate main contactors K13-14. This provides high

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Page II-12
current power to the test set output circuitry through the SCR controller. The
switched output voltage is supplied to distribution blocks DB1 and DB2.
The Vernier autotransformer T1 and output transformer T2 are connected to in-
put voltage selector switch S11. This allows for connection in series for 480 VAC,
and parallel for 208/240 VAC. Vernier T1 is connected directly to the first primary
of T2, so that clockwise rotation produces an output voltage of about 0-1.5 VAC.
Relays K3, K4, and K5 connect the second primary windings for fixed outputs of
0, 1.25, or 2.50 VAC for taps 1, 2 and 3. This provides three (3) overlapping output
ranges up to 3.75. 7.5 or 15 VAC, depending on how the four secondary windings
are connected.
Output current is detected by means of an air core CT around all four main bus-
ses. The configuration switch can be set to 1000, 2000, or 4000, which divides
the signal by a factor of 4, 2, or 1. Calibration of all three modes is accomplished
with potentiometers on the switch assembly under the output face plate.
The output section is energized when a signal is applied to the trigger board of
the SCR controller. The initial phase angle is determined by a zero-crossing de-
tector in the trigger PCB, and a delay which is normally preset to 70 degrees.
There are three solid state relays, one of which powers the Vernier assembly, and
the others power the second primary on the output transformer.
The Vernier autotransformer may be adjusted manually by means of a hand-
wheel, or by activating the motor drive. Increasing output is clockwise for all
taps.
When the SCR board is energized, 12 VDC is applied to the control panel which
is used for output ON detection and indication.
Thermistor TH2 senses the temperature of the output bus, and TH1 reads the
temperature of the first primary of output transformer T1. These normally have
a resistance of 10 K ohms at room temperature, and lower values as the temper-
ature increases.
Relays K3 through K5 are energized through the indicator control panel and the
control PCB. They may be equipped with electrical interlocks to avoid damage
if all three are simultaneously energized. The relays actually have 24 VAC coils
which are driven with a pulse of 24 VDC long enough to cause them to seal in,
and then are held by a lower current through power resistors on the control
PCB. This type of contactor is not available with a DC coil, and DC was chosen to
avoid relay chatter that can occur with AC relays if line voltage momentarily
drops.
The adjustable Vernier assembly T2 in the PI-2500 consists of a stack of four 120
VAC decks, with each series connected pair connected to a 240 VAC primary on
T1A. Minor voltage imbalance up to about 2 VAC is corrected by means of paral-
leling transformer T3, and actual current in each primary circuit is monitored by
means of 50:5 current transformers T4 and T5. Resistors R1 through R4 ensure

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-13
voltage balance on the series connected pairs, and also provide a resistive load
to stabilize the SCR controller at low output settings.
The secondary currents from T4 and T5 are monitored by the Programmable
Overload Device (POD), which also measures actual temperature in the primary
winding of T1A. The overall system status is displayed on the bar graph of the
indicator control panel, and an interlock relay shuts down the output of the test
set if abnormal conditions are detected. More details are in a separate manual.
The PI-2500 features a very efficient low impedance output transformer with
enhanced reliability and cooler operation due to single piece secondary bus
conductors. It was designed so that it could provide three connection modes
for 1000, 2000, and 4000 amps continuous current. Stab Adaptor Plates and se-
ries bars are used for convenient output connection. The output bus connectors
are slotted so that the hardware can be loosened and removed or replaced eas-
ily. A slotted brace is supplied that helps with alignment. See the following illus-
tration for details:

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Page II-14
Illustration of PI-2500 Stab Plate Assembly:
AUX5000 Main Unit Circuitry
The AUX-5000 auxiliary unit connects to a 480 VAC supply and ground by
means of standard input jacks. Primary protection is provided by 200-amp fuses
F1 and F2. Main power is supplied to the output section by power contactors K1
and K2, which are energized when those in the PI2500 are turned on. There are
three solid state relays, which control power to the three sections of the output
transformer T1. They may be protected by fuses, and they are equipped with
snubbers to prevent spurious turn-on and latching of output.
Contactors K3 through K8 are operated for taps 4 through 9, and their coils are
driven by 24 VDC pulses from the Auxiliary Relay PCB. The primary of each trans-
former section is shorted when it is not needed; otherwise it is powered through
the SSR. Electrical interlocks on the contactors assure that both cannot be
pulled in at the same time.
The control connector to the PI2500 provide ACHI and ACLO power for the fan,
control signals for the contactors, initiate signal for the solid-state relays, inter-
locks, and sense leads for the output bus voltage from terminal 1 to 4.
The secondary windings of the transformer, consisting of two pairs of bus bars,
are bolted to the secondary bus bars of the mating PI-2500. The combined units
form a transformer which is nearly identical to the PI4000B.
The high strength and corrosion resistant stainless-steel output bolts should
rarely require replacement but may be serviced by simply removing the sixteen
screws on the phenolic output faceplate, and then removing one of four bolt
retainers. The standard hex head bolts may then be pushed through and re-
placed.

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-15
PI-2500 Indicator Control Panel Circuitry
The power for the control panel is provided by the INV/2 circuit, which is the
main input voltage divided by 2. This voltage, ranging from 104 VAC to 240 VAC,
powers a wide range switching power supply, which supplies 12 VDC to the rest
of the circuitry. When the CTL ON switch S1 is pressed, DS1 lights and relay K4 is
energized, and latches on if voltage interlocks are OK and the external control
relay energizes. K4 also provides 12 VDC power to the PC board, which has cir-
cuitry for Vernier position display and adjustment, tap selection and display, and
temperature readings. Pressing S2 turns control power off.
If any external interlock is open, as sensed by K1, indicator DS4 will light. Other-
wise, K2 will energize, which energizes K2 and allow operation of S3. When MAIN
ON switch S3 is pressed, relay K3 energizes, MAIN READY lamp DS3 lights, and
power is provided to external main contactor. If it operates, K3 is latched on
through its auxiliary contact.
If the output of the test set is ON, 12 VDC will be applied to DS5, and also will be
sensed by the PC board, which will inhibit tap change.
The INV/4A and B signals provide a voltage equal to ¼ the input voltage. This is
rectified and filtered by the metering PC board and displayed on the panel me-
ter.
Output is inhibited during tap change or when an interlock condition exists. An
interlock (INTLKB) will be asserted if either temperature readouts exceed an ad-
justed setpoint.
The Vernier position signal is supplied to the PC board and displayed as a 0-
100% reading on a ten segment LED bar graph. The signal is about 1.0 to 4.0
VDC.
The bus temperature is from a 10 K ohm thermistor. System temperature is a
variable voltage from the POD, as discussed elsewhere. Circuitry in the PC board
converts these signals to voltages which are displayed on multicolor bar graphs.
When the signal exceeds that which lights one red bar, the interlock is tripped.
The output voltage of the test set is supplied at jacks J1 and J2.
Indicator Control Panel
Input Voltage Meter: This LED panel meter indicates the approximate input
voltage applied to the test set.
Control Power ON switch: This green switch turns on 120 VAC control power to
the test set, and its green lamp lights when ON.
Control Power OFF switch: This red switch turns off the 120 VAC control power

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Copyright(C) 1994-2008 Electrical Test Instruments, LLC. All Rights Reserved
Page II-16
to the test set.
Main Power READY switch: This green switch turns on the main power to the
output section of the test set, and its green lamp lights when ON.
Main Power INTERLOCK switch: This red switch turns off the main power to the
test set. It lights if an interlock condition is detected.
Output ON indicator: This yellow lamp lights when output voltage is ON.
Output Voltage jacks: These banana jacks are connected to output stabs 1 and
8 in the PI2500, and stabs 1 and 4 in the AUX-5000 and may be used to monitor
voltage on the breaker with a DMM.
Thermal Status - Bus: This multicolor bar graph indicates approximate temper-
ature of the output bus. Green bars indicate normal temperature. Yellow bars
indicate significant heating, and heavy testing should be postponed until unit
cools. Red bars indicate overheating, and unit must cool to yellow range before
testing. Output initiation will be inhibited if second red bar lights. Excessive
temperature may indicate poor output connections.
Thermal Status - System: This indicates temperature of the output section, and
other conditions, as determined by the POD. A thermistor in the winding of the
first section of the output transformer provides actual temperature, but the
POD also calculates a “virtual” temperature based on overload duty cycle limits
as indicated in the specifications. The ten bar graph LEDs correspond to tem-
peratures of approximately 80 to 280 degrees F, with about 20 degrees per bar.
Testing is allowed up to a reading of two red bars but will then be inhibited until
temperature cools to no more than four yellow bars.
Coarse Tap Switch: This rocker switch selects the coarse tap. The unit powers up
in tap 1. Pressing the switch briefly UP or DOWN will raise or lower the tap by
one. Holding it will change taps about one per second.
Coarse Tap Indicator: This seven-segment red LED indicates tap position from 1
to 9.
Vernier Indicator Bar graph: This ten-segment red LED indicates approximate
Vernier position. 0 or 1 segment lit indicates minimum position, and 9 or 10 seg-
ments lit indicates maximum position.
Vernier Adjust Switch: This rocker switch adjusts the Vernier position. Pressing
it briefly UP or DOWN causes the Vernier to move by a very small increment, for
fine control. Holding it for about a second will cause the Vernier to move very
quickly, for rapid rough adjustment.