Megger Baker DX, User Manual

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Troubleshooting
128 Baker DX 71-030 User Guide EN V10 www.megger.com
Applications: What to do First
Start by reviewing the “Common application problems” section below. In some cases, you will
be able to resolve the issue on your own.
If none of the descriptions fits your situation or they do not help you with your problem, ensure
that you have basic information about the tester and specific information about the motor being
tested available when calling or faxing Megger Baker Instruments. Example test and specific
information include:

HP rating

kW rating
 RPM rating
 Operating voltage and current
 How the item being tested is wound and/or number and type of coils

Application of motor/generator
Any information that the motor nameplate can provide is helpful. A great tool is a print out or
sketch of the waveforms displayed on the tester. If a fax is available, send a draft to (970) 282-
1010, attention: Applications.
Common Application Problems
Following are the common application-related problems. Please review the following cases.

The Surge tester will not give the desired output test voltage for the
apparatus under test.
The test motor may be too large for the instrument in use. The impedance of the windings
may be too low.
The tester may be too small in this case. Contact the Megger Applications department
for suggestions.

Separation of compared wave patterns is seen when Surge testing on coils
assumed to be good—even on brand new motors or windings. Often,
separation is seen in all three comparisons for three-phase motors, but to
varying degrees. There may not be separation throughout the whole wave
pattern.
You can see this situation in DC fields or rotating poles. Be sure the coils you are
comparing are being tested in identical configurations; for example, both coils are wound
clockwise beginning to end.
On very large equipment, slight differences in capacitance to ground may be the cause.
Test again with the black ground lead removed from the motor frame. If the separation is
now gone, capacitance to ground was affecting the test. Be sure to reconnect the black
ground lead afterwards.