12 Using the Baker ZTX with Baker AWA-IV analyzers
The Baker AWA-IV 6 kV and 12 kV, and the Baker AWA-IV 12 HO models can be used with
the Baker ZTX accessory to test armatures. However, not all Baker AWA-IV 6- and 12-kV
models are properly configured to support this accessory. Baker AWA-IV 6/12 units built
since February 2009 will work with the Baker ZTX accessory. Most Baker AWA-IV units built
since December of 2007 can be modified at the factory to work. Please contact the customer
service department if you are interested in having your unit modified to work with the Baker
ZTX accessory.
The software version of the unit must also be upgraded to 4.5.0 or higher. To determine if a
unit is capable of using the Baker ZTX accessory, contact the customer service department.
Principles of armature insulation testing
Armatures from DC motors are wound in many different ways; some are rather complicated.
However, testing armature insulation is actually very simple. The insulation of the copper to
the steel or ground wall is evaluated using the hipot test, while the turn insulation is evaluated
using the surge test.
The ground wall insulation includes the insulation isolating the commutator bars from ground
along with the insulation isolating the copper turns in the rotor slots. A unit can also have
“equalizer bars” that connect opposing commutator bars, which are also isolated from the
steel armature core.
The armature winding consists of a few turns of high capacity conductors that span slots in
the rotor and connect to the commutator bars. These conductors are insulated from each
other with the “turn insulation.” Due to vibration, thermal expansion, chemical attack, and
more the turn insulation can degrade, resulting in the turns shorting to each other.
Because the inductance of armature winding turns is so low, a special impedance-matching
transformer is used to convert the output of a Baker AWA-IV surge tester to voltage and
current levels desirable for surge testing low-inductance armature windings. Additionally,
armature windings are all in parallel, further reducing the bar-to-bar inductance, making the
impedance-matching transformer all the more important.
A change in the surge waveform of a shorted coil as compared to a reference waveform
indicates an arcing or shorted armature winding.
Typically, the reference waveform is the first coil tested. All other coils will be compared to the
reference coil. According to EASA guidelines, waveforms with a five percent or greater
difference should be considered suspect.
The Baker ZTX accessory combines hardware and software to help you determine an
armature’s insulation integrity. The hardware includes the impedance-matching transformer
and fixtures. The software facilitates the acquisition of waveforms and comparison to a
reference.
Summary of Contents for AWAIV-12
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Page 16: ...2 SKF Static Motor Analyzer Baker AWA IV User Manual About this manual ...
Page 28: ...14 SKF Static Motor Analyzer Baker AWA IV User Manual Baker AWA IV Instrument Overview ...
Page 88: ...74 SKF Static Motor Analyzer Baker AWA IV User Manual Database management and maintenance ...
Page 90: ...76 SKF Static Motor Analyzer Baker AWA IV User Manual Set up of the Baker AWA IV analyzer ...
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Page 124: ...110 SKF Static Motor Analyzer Baker AWA IV User Manual Special features of the Baker AWA IV ...
Page 166: ...152 SKF Static Motor Analyzer Baker AWA IV User Manual Typical winding faults ...
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