Applications: What To Do First; Common Application Problems - Megger Baker AWA-IV User Manual

Applications: What to do First

Review the section on common application problems. Please have basic information about the analyzer and specific
information about the motor being tested available when calling or faxing to assist sales/support personnel in
determining a solution to the problem.
Examples:
Hp rating
ƒ
kW rating
ƒ
ƒ RPM rating
ƒ Operating voltage and current
ƒ How the item being tested is wound and/or number and type of coils
Application of motor/generator
ƒ
In short, all information from the motor nameplate would be helpful. A great tool is a printout or sketch of the
waveforms displayed on the analyzer.
If a FAX is available, send a draft to 970-282-1010, attention: Applications.

Common Application Problems

There are a few common application-related problems. Please review the following cases.
1. The Baker AWA-IV will not give the desired output test voltage for the apparatus under test.
1.1. The test motor may be too large for the analyzer being used. The impedance of the windings may be too
low.
1.2. The Baker AWA-IV may be at fault in this case. Do not continue testing until you contact the Megger Baker
Instruments product service department.
2. Separation of compared surge wave patterns is seen when surge testing known-good coils, or brand new motors
or windings. Often, separation is seen in all three comparisons for three phase motors, but to varying degrees.
2.1. Generally, this is caused by unbalanced impedance in windings, which is inherent to the design. It most
commonly occurs in basket or concentric wound motors. The phases are not magnetically balanced due to
different coil lengths.
2.2. When acceptance testing, waveforms that are separated because of improper turn counts, misconnections,
or reversed winding groups may be seen.
2.3. This condition may also be seen in DC fields or rotating poles. Coils being compared must be tested in
identical configurations.
2.4. On very large equipment, slight differences in capacitance to ground may be the cause. At low voltage
levels, begin the test again with the black ground lead removed from the motor frame. If the separations
disappear, the problem was capacitance to ground. Be sure the winding has passed the DC tests before
doing the Surge test.
3. There is no dampened sinusoidal wave pattern on the display when testing a coil. The wave pattern rises on the
left and then slowly drops as it trails off to the right of the screen. It may or may not cross the zero/base line.
3.1. The coil under test is probably too high an impedance to get a good working pattern. The coil may be very
high in resistance.
3.2. A broken test lead may be the cause. Under heavy use, test leads should be checked weekly to ensure that
there is no breakage. Grasp the boot and clip in one hand while pulling on the lead with the other hand. A
broken lead will stretch, whereas a good lead will not.
134 Baker AWA-IV 71-015 EN V16 User Guide www.megger.com