SKF AWAIV-12, Руководство пользователя

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Factors that affect tester output
Sometimes full output of the tester can be below its rated maximum output voltage. This
occurs on low-impedance devices or devices that exceed the tester’s capability.
For example, the horsepower of a motor might be too high. In this case, a 12,000 V tester
might only apply 4000 V when the output is set halfway between min and max . At this mid-
point, 6000 V is expected. The tester might then give only a maximum output of 7000 V
when 12,000 V is expected.
The test should be considered successful if the desired test voltage level can be reached. For
the example above, if the motor was 3000 horsepower and operated at 2300 V, an
appropriate test voltage would be 2 x 2300 V + 1000 V = 5600 V. The size of the motor can
limit the tester’s output to a level below its rating.
• Adjacent windings such as a start winding, part winding, high-voltage, or low-
voltage winding should be jumpered together and in many cases grounded while
doing the test. This procedure can eliminate incorrect test results caused by
inductive coupling.
Table 7. Common testing issues and effects.
Factor Effect
Motor larger than
recommended max size to
test
Capacitance and inductance of motor windings can load the
tester output down. The voltage output is reduced below
maximum output, which can damage the tester if the test is
applied for an extended period.
Note: The test is considered successful if the test voltage 2E
+ 1000V is achieved.
Motor rated RPM is slow. For each reduction of the motor’s RPM, (i.e. 3600 -> 1800)
the effective horsepower of the motor that the tester senses
is doubled.
Example: A 500 hp/3600 RPM motor = 500 hp.
A 500 hp/1800 RPM motor = 1000 hp.
A 500 hp/900 RPM motor = 2000 hp, etc.
Motor has high number of
poles
Same condition as comment above on motor RPM.
Feeder cable length Distributed capacitance of the feeder cable loads down the
test according to the formula:
cap Cable Cap Tester
cap tester tester V
capable V
+
×
= max
The tester may be unable to generate the desired test
voltage. It is observed that the closer the motor is to the
recommended maximum motor size to test, the shorter the
feeder cables must be. If the motor is very small compared
to the maximum recommended motor to test, the tester
may have sufficient energy such that longer feeder cables,
as well as the motor windings, can be tested.
Shielded feeder cable The above condition becomes extreme. Shielded feeder
cables have very high capacitance.
SKF Static Motor Analyzer—Baker AWA-IV User Manual 149
Typical winding faults