Baker D30R User manual

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Users Manual
Digital Winding Tester
D30R
Baker Instrument Company, an SKF Group Company,
4812 McMurry Ave. Suite 100
Fort Collins, CO 80525
[phone]
[phone] (FAX)
800-752-8272 (USA Only)
Note: This equipment has been tested and found to comply with the limits for a Class A digital
device, pursuant to Part 15 of the FCC rules. These limits are designed to provide reasonable
protection against harmful interference with the equipment is operated in its installation. This
equipment generates uses and can radiate radio frequency energy and, if not installed and used in
accordance with the product manual, may cause harmful interference to radio communications. If
this equipment does cause harmful interference, the user will be required to correct the
interference.
Due to the phenomena being observed and the material properties being measured, this
equipment does radiate radio frequency energy while in the active test mode. Care should be taken
to insure this radio frequency energy causes no harm to individuals or other nearby equipment.
Information furnished in this manual by Baker Instrument Company, an SKF Group Company,, is
believed to be accurate and reliable. However, Baker Instrument Company, an SKF Group
Company, assumes no responsibility for the use of such information or for any infringements of
patents or other rights of third parties that may result from its use. No license is granted by
implication or otherwise under any patent rights of Baker Instrument Company, an SKF Group
Company.
Warning:
Baker Instrument Company, an SKF Group Company, assumes no liability for damages consequent
to the use of this product. No part of this document may be reproduced in part or in full by any
means such as photocopying, photographs, electronic recording, videotaping, facsimile, etc.,
without written permission from Baker Instrument Company, an SKF Group Company, Fort Collins,
Colorado.

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Warranties; Disclaimers
Limited Warranty as to Baker/SKF
Brand Products.
a) Baker/SKF warrants that
Baker/SKF brand Products, if any,
that are sold under the Agreement
shall be of the kind and quality
described in Baker/SKF's
acknowledgment of Buyer's Order,
and shall be free of material
defects in workmanship and
material for a period from the date
of shipment equal to (i) twelve (12)
months in the case of new
Products (including factory-
installed circuit boards, accessories
and options purchased concurrently
with the applicable Product), (ii) six
(6) months in the case of used or
refurbished Products, and new
circuit boards, accessories and
options delivered separately from
the applicable Product, (iii) a period
of ninety (90) days from the date
of shipment in the case of used or
refurbished circuit boards. If any
such Product , accessory or option
is not as warranted, Buyer must
notify Baker/SKF thereof in writing
within the applicable warranty
period.
b) Baker/SKF's sole obligation, and
Buyer's sole remedy, under the
foregoing warranty shall be to
provide the parts and labor for the
repair or replacement (at
Baker/SKF's sole option) of
defective parts, recalibration of
any portions of a product that
could reasonably have been
affected by the repair, and
functional verification to affirm
proper operation. When, subject
to the next sentence, the Buyer
returns Products, accessories or
options to the Baker/SKF factory
for warranty service, Baker/SKF
will bear the cost of return
packaging, and shipping , and
insurance ,on the return shipment.
For Products, accessories or
options that Baker/SKF designates
as “on-site service only” due to
their size, the permanence of their
installation pr otherwise, travel
expenses (including labor costs for
time spent traveling) for warranty
services are covered to the
location of original shipment and
installation. Products, accessories
and options that are capable of
being returned to the factory for
service may receive warranty
service on site, but all travel
expenses (including labor charges
for time spent traveling) shall be
the responsibility of Buyer.
c) For warranty coverage of “on-site
service only” items, Buyer must
make available to Baker/SKF a
knowledgeable operator to assist
with preliminary diagnosis prior to
a service trip being scheduled.
Buyer, in connection with a
request for on-site service, must
be capable of authorizing charges
for the service visit in the event
the issues discovered are not
covered by warranty, such as
application errors or installation
errors. If Buyer, having elected to
perform installations without
Baker/SKF’s participation and
having encountered irresolvable
problems, shall be charged for an
installation if on-site assistance is
necessary, except when defective
product is determined to be the
cause.
Trademarks
All other trademarks, service marks or
registered trademarks appearing in this
manual are the trademarks, service
marks or registered trademarks of their
respective owners.

Table of Contents
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Users Manual ........................................................................................................................................... 1
Warranties; Disclaimers ......................................................................................................................... 2
Limited Warranty as to Baker/SKF Brand Products. .................................................................... 2
Trademarks .............................................................................................................................................. 2
Preface............................................................................................................................................................... 7
Important safety information.....................................................................................................................7
General Safety Precautions ...................................................................................................................7
Safety term definition.............................................................................................................................7
Other Important Safety warnings.........................................................................................................8
Symbols on equipment........................................................................................................................... 9
Other Information........................................................................................................................................9
Cleaning & decontamination..................................................................................................................9
Technical assistance / Authorized Service Centers ............................................................................ 9
Accessory interconnection and use ......................................................................................................9
Intermittent operation limits.................................................................................................................. 9
Installation requirements ....................................................................................................................... 9
Unpacking the unit .................................................................................................................................. 9
Pollution Degree II.................................................................................................................................10
Power requirements .............................................................................................................................10
Environmental conditions.....................................................................................................................10
Declaration of Conformity ........................................................................................................................11
1........................................................................................................................................................................13
Instrument Overview.....................................................................................................................................13
Front panel controls..............................................................................................................................13
Initial power-up and check-out...........................................................................................................16
Using the footswitch..............................................................................................................................16
2........................................................................................................................................................................17
Test sequence, voltages & applicable standards.......................................................................................17
Recommended testing sequence ........................................................................................................17
1) Coil Resistance test ..........................................................................................................................17
2) Megohm test .....................................................................................................................................17
3) Principles of the Dielectric Absorption (DA) test..........................................................................17
4) Principles of the Polarization Index (PI) test.................................................................................17
5) DC HiPot test.....................................................................................................................................18
6) Surge test ..........................................................................................................................................18
Recommended test voltages – HiPot and Surge tests....................................................................18
Applicable Standards ............................................................................................................................20
3........................................................................................................................................................................21
Coil Resistance testing ..................................................................................................................................21
Principles of Coil Resistance testing .......................................................................................................21
Resistance Test Display........................................................................................................................21
Resistance test checklist.......................................................................................................................21
Auto ranging Resistance measurement algorithm ..........................................................................22
Saving & recalling measurements......................................................................................................23
Indications of problems in a motor.....................................................................................................23
4........................................................................................................................................................................25
Principles and theory of DC testing.............................................................................................................25
Principles of DC testing.............................................................................................................................25
5........................................................................................................................................................................29
Performing high voltage DC tests ...............................................................................................................29
The test display..........................................................................................................................................29
Other Important Safety warnings.......................................................................................................30
General user notices .............................................................................................................................31
High voltage DC test checklist .............................................................................................................31
DC testing...........................................................................................................................................31

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Full DC testing of a motor....................................................................................................................31
Performing only a Megohm test.....................................................................................................34
Performing only DC over voltage test (DC HiPot test) ....................................................................34
Sample data showing good & poor insulation ..................................................................................35
Storing the test results in memory ....................................................................................................35
Using the footswitch..............................................................................................................................35
The HiPot over current trip indicator.................................................................................................35
Effects of temperature .........................................................................................................................36
Step Voltage test ...................................................................................................................................36
Step Voltage test procedure................................................................................................................36
6........................................................................................................................................................................39
Principles and theory of Surge testing .......................................................................................................39
Principles of Surge testing...................................................................................................................39
Surge testing theory .............................................................................................................................39
Determination of a fault.......................................................................................................................40
Motivation for Surge testing................................................................................................................41
Contact bounce......................................................................................................................................41
Lightening strikes ..................................................................................................................................41
Inverter transients.................................................................................................................................41
Line surges.............................................................................................................................................41
IGBT switching technology...................................................................................................................42
7........................................................................................................................................................................43
Performing Surge tests.................................................................................................................................43
Surge test display..................................................................................................................................43
Other Important Safety warnings.......................................................................................................44
General notices ......................................................................................................................................45
Surge test setup....................................................................................................................................45
Three phase motor check list ..............................................................................................................46
Single coil surge test and set-up........................................................................................................47
Example: Comparison to a master coil ..........................................................................................49
8........................................................................................................................................................................51
Surge test applications..................................................................................................................................51
Other Important Safety warnings.......................................................................................................51
Maintenance testing..............................................................................................................................52
Determination of a fault.......................................................................................................................53
Open Circuits..........................................................................................................................................53
Form coils ...............................................................................................................................................54
Notes and tips for form coils...........................................................................................................54
Three phase motors..............................................................................................................................54
Two or more single coils ......................................................................................................................55
Notices for two single coils ..............................................................................................................55
Wound rotor motors.............................................................................................................................55
Synchronous motor/generator............................................................................................................56
Faults in synchronous motor/generators ..........................................................................................56
Pole piece fault..................................................................................................................................56
Stator winding fault..........................................................................................................................56
Chiller motor testing .............................................................................................................................56
Field coils ................................................................................................................................................56
Armatures...............................................................................................................................................56
Bar-to-bar surge test ......................................................................................................................57
Span testing.......................................................................................................................................57
Determination of a fault...................................................................................................................58
Notes and tips for span testing armatures...................................................................................58
Testing large AC stators/motors .........................................................................................................59
Notes and tips for large AC stator/motors....................................................................................59
Rotor loading (coupling) when testing assembled motors..............................................................60
Testing assembled motors from the switchgear..............................................................................60

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Transformers .............................................................................................................................................61
Single phase transformers ..............................................................................................................62
Three phase transformers...............................................................................................................62
Determination of a fault...................................................................................................................62
9........................................................................................................................................................................63
Documenting tests.........................................................................................................................................63
Store........................................................................................................................................................63
Store Resistance data...........................................................................................................................64
Store HiPot and PI data .......................................................................................................................64
Store Surge data...................................................................................................................................64
Recall.......................................................................................................................................................66
Recall Resistance data..........................................................................................................................66
Recall HiPot data...................................................................................................................................67
Recall Surge data ..................................................................................................................................67
Print.........................................................................................................................................................68
Clear ........................................................................................................................................................68
Erase .......................................................................................................................................................68
Compatible printer information...........................................................................................................69
Appendix A Winding Faults...........................................................................................................................71
Appendix B......................................................................................................................................................73
Troubleshooting .............................................................................................................................................73
Notices for proper and safe operation ...............................................................................................73
Self help and diagnostics......................................................................................................................73
Step #1: Basic information................................................................................................................73
Step #2: Applications or service problem?......................................................................................73
Applications: What to do first!............................................................................................................74
Common application problems............................................................................................................74
Service: What to do first? ...................................................................................................................76
Open condition display..........................................................................................................................76
HiPot display checks..............................................................................................................................76
HiPot over current trip check ..............................................................................................................77
Open ground check ...............................................................................................................................77
Limited output surge waveform .........................................................................................................77
Warranty return ....................................................................................................................................77
Appendix C Technical specifications and calibration.................................................................................79
Technical specifications.............................................................................................................................79
Accuracy of measurements - Coil Resistance test...........................................................................79
HiPot measurement accuracy – HiPot voltage.................................................................................80
Testing Accuracy - HiPot Measurements..........................................................................................80
Voltage measurement accuracy – Surge (D30R).............................................................................80
Calibration information.........................................................................................................................80
Index ................................................................................................................................................................81

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Preface
Important safety information
General Safety Precautions
Note: The general safety information presented here will be for both operating and service
personnel. Specific warnings and cautions will be found throughout this manual where they
apply.
Note: If the equipment is used in any manner not specified by Baker Instrument Company,
an SKF Group Company, the protection provided by the equipment may be impaired.
Safety term definition
DANGER: Indicates a hazardous situation which, if not avoided, will result in death or serious
injury.
WARNING: Indicates a hazardous situation which, if not avoided, could result in death or
serious injury.
CAUTION: Indicates a hazardous situation, which, if not avoided, could result in minor or
moderate injury.
NOTICE: “NOTICE” is the preferred signal word to address practices not related to personal
injury.
Danger
High Voltage
To prevent serious injury or death:
-Do not use in explosive atmospheres.
-Do not contact test leads or device being testing
while test is in progress or during discharge period.
-Do not connect test leads to live circuits.
Read and follow safety precautions and safe operating
practices in operator manual. Do not exceed maximum
operating capabilities of this instrument.

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Other Important Safety warnings
Failure to follow these precautions could result in severe electrical shock or death.
1) Never attempt a two-party operation. Always know what test is being performed
and when. FOR EXAMPLE: DO NOT adjust test leads when footswitch is being
operated. Leads will have live voltage and severe electric shock may result.
2) For capacitor-started motors or systems with surge arrestors/power factor
capacitors, be sure to disconnect all capacitors from the test circuit before testing.
3) Upon completion of a DC High Potential, Megohm, Polarization Index, Step Voltage,
Dielectric absorption, or Continuous Ramp test, before disconnecting the test leads,
short the winding, motor, etc., to ground and allow time for discharge. If this is not
done, voltage may still be active on leads and tested components.
4) Make sure the tester leads are disconnected before the motor is energized or
powered up.
5) Do not remove the product covers or panels or operate the tester without the
covers and panels properly installed. Components on inside of tester carry voltage
for operation and if touched can render a shock.
6) Use appropriate safety equipment required by your organization, including high
voltage globes and eye protection.
7) Repair Parts Warning: Defective, damaged, or broken test leads must be replaced
with factory-authorized parts to ensure safe operation and maintain performance
specifications.
8) Ground the product: This product is grounded through the grounding conductor of
the power cord. To avoid electrical shock, plug the power cord into a properly
wired/grounded receptacle before connecting the product test leads.
Danger from loss of ground – Upon loss of the protective ground connection,
all accessible conductive parts, including knobs and controls that may appear
to be insulated, can cause an electric shock!
9) This instrument is NOT waterproof or sealed against water entry.
10) The unit is for indoor use. If used outdoors, the unit must be protected from rain,
snow and other contaminants.
Fig Pre-1: Safety Labeling D30R

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Symbols on equipment
Protective conductor terminal. Located beside black ground test lead
on front panel of instrument.
Earth (ground) terminal
Frame or chassis terminal. Located on rear panel of instrument by
ground terminal.
Warning about hazardous voltage and risk of severe electrical shock or
death. Located beside each red test lead on front panel of instrument.
Other Information
Cleaning & decontamination
The D30R should be kept clean and in a dry environment. To clean the unit, power down and
unplug the instrument. Wipe with a clean water dampened cloth. Do not submerge in water
or other cleaners or solvents. To clean the screen, take a soft water dampened cloth and
gently wipe the surface.
Technical assistance / Authorized Service Centers
See our website at www.bakerinst.com for technical assistance/authorized service center
information. This information will be marked with an asterisk.
Accessory interconnection and use
The D30R are equipped with a footswitch standard. Please see details about these accessories
in later chapters in this manual.
Intermittent operation limits
At this time there are no intermittent operation limits to the use of the AWA unit.
Installation requirements
The unit may be operated
1) Flat on the bottom of the unit,
2) Flat on the back of the unit, or
3) Held at an angle using the rotating handle.
There are no ventilation requirements.
The unit is intended for use in Installation Category II (Portable Equipment) areas and
pollution Degree II Environments where occasional non-conducting condensing pollution can
be encountered.
Unpacking the unit
Carefully remove the following items from the shipping boxes.

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D30R
Power cord
Operation manual
Pollution Degree II
(From IEC 61010-1 3.6.6.2) Only non-conductive pollution occurs. However, temporary
conductivity caused by condensation is expected.
Power requirements
Using the provided AC power cord, connect the unit to a grounded AC power source. The
unit’s power requirements are 100-240VAC, 50-60 Hz, 2 amps AC maximum current draw.
The unit is fused using 2.5A fast blow fuses. Replace fuses with like type and rating.
Environmental conditions
1) The unit has been tested for use up to 2000 m.
2) The tester should only be operated in temperatures ranging from 41 to 104
degrees Fahrenheit (5° C to 40° C).
3) This unit is for use at a maximum relative humidity of 80% for temperatures up to
31 °C decreasing linearly to 50% relative humidity at 40°C. This unit is intended for
Installation Category II in a Pollution Degree II environment.

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Declaration of Conformity
Manufacturer’s Name & Address:
Baker Electrical Instrument Company, an SKF Group Company,
4812 McMurry Ave
Fort Collins, CO 80525
USA
Equipment Description: Testers for Surge, DC Hi-Pot, and Winding Resistance of motors.
Equipment Model Designations: D30R.
Application of Council Directive 72/23/EC on the harmonization of the laws related to Member
States relating to electrical equipment designed for use within certain voltage limits, as
amended by: Council Directive 93/68/EC and Council Directive 2004/108/EC on the
approximation of the laws related to Member States relating to the electromagnetic
compatibility, as amended by: Council Directive 93/68/EC. Note: due to the phenomena being
observed and the material properties being measured, this equipment does radiate radio
frequency energy while in the active test mode.
Referenced Safety Standards:
EN 61010-1
Referenced EMC Standards:
EN 61326:2001
EN 55011 Class A
EN 61000-3-2
EN 61000-3-3
EN 61000-4-2
EN 61000-4-3
EN 61000-4-5
EN 61000-4-5
EN 61000-4-6
EN 61000-4-11
I, the undersigned, hereby declare that the equipment specified above conforms to the above
Directives and Standards.
Signature:
Printed Name: John S. Wilson
Title: Manager, Standard Products.

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1
Instrument Overview
Front panel controls
1) Printer port:
A parallel port for printing waveforms and summaries displayed by the Digital Tester is
available. This port may also be used for interfacing with the Motor Test Acquisition for
Windows program (MTA for Windows) on a personal computer.
2) Function keys
Function key for data collection, recall, and printing of tests. The keys correspond to choices
provided on the CRT display below them. See the chapter on Storage and Print Capabilities,
for a detailed description of the tester’s storage capability.
3) CRT display
The Cathode Ray Tube (CRT) is the location where the tester displays test information. At the
Top, menus corresponding to the four function keys above the CRT are shown. The main
portion of the screen displays the waveforms being measured and/or recalled with
corresponding graticules for reference. The bottom portion shows the volts/division for the
waveform, the name of the test on display, and the micro-seconds/division (micro-
amps/division for HiPot tests). When using the function keys, the screen will display options
pertinent to the storage, recall, and print capacities of the unit. Error messages are also
displayed here.
4) Emergency stop switch
5) Block port

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6) Test
The Test button activates the high voltage output of the tester. One of the selected modes,
Surge, or HiPot will be enabled and a voltage will be impressed on the device being tested.
This button automatically disengages when released.
7) Open ground warning light
When the AC line source is not properly grounded, the red Open Ground light will illuminate.
The test set will power up, but high voltage will be withheld by internal electronics.
8) HiPot trip warning light
This lamp illuminates to indicate a DC HiPot trip circuit has stopped the test. The red lamp
will stay illuminated until the test button is released.
9) Intensity
Rotation of this control will adjust the intensity or brightness of the display. Clockwise (CW)
will increase intensity. Counterclockwise (CCW) will decrease intensity. Intensity has a slight
effect on the focus and can be adjusted to a blank screen.
10) Vertical position
This control adjusts the up or down positioning of the surge wave pattern. Optimum
positioning is usually on the center of one major graticule line below center for surge testing.
11) Horizontal position
This control adjusts the side to side positioning of the surge wave pattern. A trace beginning
at the far left is suggested for surge testing.
12) Function selector
This control selects the type of test to be performed and the sensitivity of the DC HiPot
leakage current display. The name of the test chosen is displayed on the lower portion of the
CRT for reference. There are four primary positions as follows.
Aux: The auxiliary position is for the D30R is used for Surge and HiPot modes.
Surge: This position selects the Surge Test. The name of the test and the microseconds per
division measured is displayed on the lower portion of the CRT for reference. A digital readout
for the peak voltage of the test is also displayed in the upper right portion of the screen for
reference.
HiPot- μA/div This position is used for DC HiPot testing. The name of the test is displayed on
the lower portion of the CRT for reference. A digital readout for the leakage current (in micro-
amps) of the test and the resultant resistance in mega-ohms is also displayed on the screen
for reference. There are three positions associated with the HiPot test. The three positions
are 100uA/div, 10uA/div, and 1uA/div. The chosen micro-amps per division setting is
displayed on the lower right portion of the CRT for reference during testing u-Amps/Div
controls the sensitivity of the current displayed. It also automatically selects the overcurrent
trip point, which will be ten times these settings or 1000, 100, and 10 micro-amps
respectively.
13) Volts/div
This control sets the sensitivity of the display or scale factor in volts per division for both the
Surge and DC HIPOT traces. There are four settings corresponding to 1250, 2500, 5000, and
7500 volts per division. Note: this knob setting does not limit the output voltage of the tester.
14) Seconds/div

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NOTICE
For the surge test, with the SECONDS/DIV control at the lowest possible setting, the
ringing pattern must be at lease one division in length for one full cycle. Less than one
division for the first cycle indicates a very low inductive load. DAMAGE to the
instrument is possible when operated more than ten (10) seconds into a low inductive
load.
This control adjusts the seconds per division or sweep rate of the trace on the horizontal axis
of the surge display. There are ten settings corresponding to 2, 6, 10, 20, 60, 100, 200, 500
micro-seconds and 1 and 2 milli-seconds per division. The seconds per division setting is
displayed on the lower right portion of the display for the reference during Surge Testing.
This control will have the effect of zooming in or out on the wave pattern.
15) Kelvin Resistance test connector
16) Output control
This control adjusts the output voltage of the tester. Clockwise (CW) rotation increases output
and counterclockwise (CCW) rotation decreased output. Full CCW is the MIN (minimum) point
output and full CW is MAX (maximum) or 100% of the testers rated output.
Note: A “Zero Start Interlock” is connected to the output control for use during Surge and
HiPot testing. The user must return the output control to MIN each time before pressing the
Test button (6). In other words, if the Test button is pressed while the Output control is
above zero the instruments output is disabled until the Output control is rotated to MIN.
17) Line in
The external AC power supply plug.
18) On/OFF
On/Off switch
19) Leads energized indicator light (2 lights)
These indicator lights will illuminate when voltage is applied during a test.
20) Surge/HiPot selector
This function, like Function selector (12), is a relay that selects the type of test, Surge or
HiPot, to be performed. The name of the test chosen is displayed on the lower portion of the
CRT for reference.
Note: For testing windings and stators, it should always agaree with the position of the
Function selector.
21) Three phase selector switch
This is an optional high-voltage rotary switch that selects which test lead is hot, open, or
ground. If this switch is present on the tester, refer to Appendix D: Three Phase Operation for
a description and instructions to use this switch for surge testing.
22) Test leads (lower right side)
Test leads, one red and three black or ground leads, are provided for contact to the windings.
Test leads are insulated to 60kV.
23) Footswitch connector (rear panel)
A footswitch may be connected to this socket which is in parallel to the Test button. The
footswitch will operate the tester in a manner identical to the Test button, freeing the user’s
hands from having to operate the switch.

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24) E-stop lights connector
Port for external large lights that fit on top of unit for added safety.
Initial power-up and check-out
Note: Each Baker Instrument Company, an SKF Group Company Tester incorporates a
supply ground detection circuit. This circuit assures a positive grounding of the tester. If the
instrument is not properly ground, the OPEN GRN indication will light and testing cannot
proceed. Check the supply to the tester (broken ground, bad extension cord, excessive ground
to neutral voltage) and assure that a low impedance ground is provided to the unit.
1) Check that the On/Off switch is in the Off position.
2) Connect the tester power cord to a 110-120 VAC outlet (or 220-240 VAC outlets if
appropriate). The tester will work on either 60 Hz or 50 Hz.
3) Set the Output control to Min (fully counterclockwise).
4) Turn the tester On/Off switch to On. Allow a brief period for CRT warm-up. The
following message should appear on the screen.
A self-test performed on the tester for all internal memory modules when the tester is
powered up. Any failures will be noted on the CRT display.
Using the footswitch
The Digital tester can be equipped with a footswitch that allows hands free operation of the
instrument. For example it is used to help eliminate the display effect of rotor loading, by
allowing the operator to spin the rotor of the equipment under test.

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2
Test sequence, voltages &
applicable standards
Recommended testing sequence
In order to test motors adequately and to have effective predictive maintenance programs,
Baker Instrument Company, an SKF Group Company, suggests using a specific test sequence.
The general idea is to perform the test sequence as a series of progressively more rigorous
tests, accepting the idea that if a test fails, troubleshooting and repair should begin at that
time. Further, more rigorous testing should only commence after satisfactory diagnosis and/or
repair.
The suggested testing sequence is: (1)Resistance test, (2)Meg-ohm, (3)HiPot and finally (4)
Surge.
1) Coil Resistance test
A coil resistance test looks for resistance imbalance between phases, discrepancies between
measured resistance values, previous measurements and nameplate values. If a problem is
found, the motor should be inspected for the cause of the discrepancies. Typical problems
that may exist are 1) hard shorts to the motor’s core, 2) hard shorts between coils either
within the same phase or between phases, 3) coils rewound with the improper gauge wire, 4)
loose or corroded connections. Further HiPot or Surge testing is not necessary until the
resistance measurement is acceptable.
2) Megohm test
A Megohm test is performed using a test voltage based on the operating voltage of the motor
and the appropriate standards/company testing guidelines. Look for an unusually low
Megohm value when compared to previous measurements or industry accepted limits for the
type of insulation in the motor. If a low Megohm value is measured, the motor should be
inspected for ground wall insulation damage. Some part of the ground wall insulation has
failed. Possible problems include: 1) slot liner insulation or enamel wire insulation may be
burned or damaged, 2) the motor might be full of dirt, carbon dust, water or other
contaminates, 3) connections to the actual coils may be bad, 4) wrong insulation may have
been used to connect the coils to the motor’s junction box, etc. No further testing is necessary
until the reason for low meg-ohm readings is found and corrected.
3) Principles of the Dielectric Absorption (DA) test
The Dielectric Absorption (DA) test is essentially a short-duration PI test and is usually
intended for smaller motors. Larger motors whose insulation does not easily polarize are also
good candidates for the DA test. Other than the shorter test time, all other principles are the
same as the PI test, explained in the next section.
While the PI test is recommended only for motors 200 horsepower or greater, the DA test is
useful for motors in approximately the 50 to 200 horsepower range. The DA value is the ratio
of the ground wall insulation resistance (IR) at 3 minutes to the IR value at 30 seconds.
4) Principles of the Polarization Index (PI) test
The Polarization Index test (PI test) is the most confusing HVDC test in use due to the
subtleties in the interpretation of the results. The PI test is performed in order to
quantitatively measure the ability of an insulator to polarize. When an insulator polarizes, the
electric dipoles distributed throughout the insulator align themselves with an applied electric
field. As the molecules polarize, a “polarization current”, also called an absorption current, is

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developed that adds to the insulation leakage current. This additional polarization current
decreases over time and drops to zero when the insulation is completely polarized.
The PI result becomes confusing when attempting to attribute variations in the PI value to the
polarizability of the insulator or other affects such as humidity or moisture, surface leakage or
instrument error. The result is even more confusing when attempting to reconcile a PI of 1
when one is expecting some other PI.
The PI test is typically performed at 500, 1000, 2500 or 5000 volts, depending on the
operating voltage of the motors being tested and takes 10 minutes to complete. The PI value
is calculated by dividing the insulation resistance at 10 minutes by the resistance at 1 minute
as shown below:
In general, insulators that are in good condition will show a “high” polarization index while
insulators that are damaged will not. IEEE 43-2000 recommends minimum acceptable values
for the various thermal classes of motor insulation.
Unfortunately, most the insulating materials developed recently (last 20 years) do not
easily polarize. For example the newer inverter grade wires and epoxy resins do not readily
polarize. As recommended in IEEE 43-2000, if the one-minute insulation resistance is greater
than 5000Mohms, the PI measurement may not be meaningful.
To address the situation where the PI may not be meaningful, the Dielectric Absorption
(DA) is widely used instead. The DA is the IR value at 3 minutes divided by the IR value at 30
seconds. The motivation for even doing the DA test is to reduce the test time to 3 minutes
instead of 10 minutes for the PI test when the PI test may not be worthwhile. To date there
are no accepted values for the DA. However, some usefulness can be obtained by trending
the DA value over time.
5) DC HiPot test
A DC HiPot test is performed using a test voltage that is substantially higher than the
Megohm Test, but, once again, based on operating voltage of the motor and the appropriate
standards/company guidelines. Look for unusually high leakage currents or a leakage current
that doesn’t stay constant or intermittently jumps up and down. Breakdowns or high leakage
currents are an indication of damaged ground wall insulation. Inspect the motor’s slot liner,
wedges, conductors between the junction box and the coils, etc.
6) Surge test
A Surge test is performed on each phase of the motor, again using an appropriate test
voltage based on the operating voltage of the machine and the appropriate
standards/company guidelines. Look for a jump to the left of the surge waveform pattern as
the test voltage is increased. This is the signature of the turn – to – turn short. If a jump is
observed, an inspection of the motor should be made to look for damaged insulation between
adjacent conductors. The insulation may be hard to see visibly, so the motor may have to be
disassembled to find the problem. If no jump in the wave patterns is observed, the likelihood
of motor failure due to insulation failure is greatly reduced.
Recommended test voltages – HiPot and Surge tests
Recommended test voltages for HiPot and Surge testing a motor, generator or transformer
are twice the AC line voltage plus 1000 volts. This test voltage is consistent with NEMA MG-
1, IEEE 95-1977 (for test voltage greater than 5000 volts), and IEEE 43-2000 (test voltages
less than 5000V).
View the tables below for a comparison of IEEE 95, EASA DC HiPot, IEEE522 Surge Testing,
IEC 34-15 and Baker recommended testing voltages. Note: Representations of motors are
listed. The formulas to calculate voltages are also listed so that test voltage of any size motor
can be calculated.
min)1(
min)10(
IR
IR
PI =

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IEEE 95-1977
EASA DC HiPot
V Line Per Unit New 3.4*Vline +1700 In Service 65% of New
480 392 3332 2165.8
575 469 3655 2375.75
600 490 3740 2431
2300 1878 9520 6188
4160 3397 15844 10298.6
6900 5634 25160 16354
13800 11268 48620 31603
IEEE 522 Surge Testing
V Line Per Unit New 3.5* pu In Service 75% of New
480 392 1372 1029
575 469 1643 1232
600 490 1715 1286
2300 1878 6573 4930
4160 3397 11888 8916
6900 5634 19718 14789
13800 11268 39437 29578
IEC 34-15
V Line Per Unit 1.2 x 50 4E +5000 0.2us 65%
480 392 6920 4498
575 469 7300 4745
600 490 7400 4810
2300 1878 14200 9230
4160 3397 21640 14066
6900 5634 32600 21190
13800 11268 60200 39130
Baker Instrument Company, an SKF Group Company
V Line Per Unit In Service 2E + 1000
480 392 1960
575 469 2150
600 490 2200
2300 1878 5600
4160 3397 9320
6900 5634 14800
13800 11268 28600
Note: Although the CRT display is accurately calibrated, it is not possible to set the voltage
exactly. It is suggested that the test voltages be rounded off to the nearest graticule
discernable on the display.
V Line Per Unit Min Test Vline*1.25 x 1.7 Max Test Vline * 1.5 x 1.7
480 392 1020 1224
575 469 1222 1466
600 490 1275 1530
2300 1878 4888 5865
4160 3397 8840 10608
6900 5634 14663 17595
13800 11268 29325 35190

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Applicable Standards
−EASA Standard AR100-1998 Recommended Practice for the Repair of Rotating
Electrical Apparatus
−IEC 60034-1 (1999-08) Consolidated Edition, Rotating Electrical Machines Part I: Rating
& Performance Ed. 10.2
−IEEE 43-2000 Recommended Practice for Testing Insulation Resistance of Rotating
Machinery
−IEEE 95-1977 Guide for Insulation Maintenance of Large AC Rotating Machinery
−IEEE 112-1991 Test Procedures for Polyphase Induction Motors and Generators
−IEEE 113-1985 Guide on Test Procedures for DC Machines
−IEEE 115-1983 Test Procedures for Synchronous Machines
−IEEE 429-1972 Evaluation of Sealed Insulation Systems for AC Electric Machinery
Employing Form-Wound Stator Coils
−IEEE 432-1992 Guide for Insulation Maintenance for Rotating Electrical Machinery (5hp
to less than 10,000hp)
−IEEE 434-1973 Guide for Functional Evaluation of Insulation Systems for Large High-
Voltage Machines
−IEEE 522-1992 Guide for Testing Turn-To-Turn Insulation on Form-Wound Stator Coils
for Alternating-Current Rotating Electric Machines.
−NEMA MG1-1993 Motors & Generators
Reprints or EASA standards are available from:
www.easa.com
1331 Baur Boulevard
St. Louis, MO 63132
Phone: [phone]
FAX: [phone]
Reprints of IEC standards are available from:
International Electrotechnical Commission (IEC)
www.IEC.ch
Reprints of IEEE standards are available from:
IEEE Customer Service
445 Hoes Lane
P.O. Box Piscataway, NJ 08855-1331
Phone: [phone]-IEEE
Fax: [phone]
www.ieee.org
Reprints of NEMA standards are available from:
National Electrical Manufacturers Association (NEMA)
Global Engineering Documents
Phone: [phone]
International: 303-379-2740