ALL-TEST PRO AT31, Руководство пользователя

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ALL-TEST
PRO ®
31 User Manual
©2011, ALL-TEST
Pro,
LLC
www.alltestpro.com
rev 2011-11F
30
Table 3: Insulation Resistance Values (IEEE 43-2000)
Application Pass/Fail Value
Insulation systems prior to 1974 > 1 Meg-Ohm + 1 Meg-Ohm per kV rating of motor
Random Wound motors less than 600 V > 5 MegOhms
DC Armatures and Form Wound motors over 600 V > 100 MegOhms
Additional Data Interpretation Considerations Three Phase Motors
There are three additional considerations when using an ALL-TEST
PRO®
31:
·
Test location
·
Rotor windings
·
Confirming winding faults
Test Location
If a fault is detected when testing from the motor control center, motor disconnect, or from any distance
away from the motor through cabling, it is important that a confirmation test be performed at the motor
connection box prior to condemning a winding.
Note: ALL-TEST PRO® MCA instruments will detect
cable faults.
·
If the readings are good at the motor during the confirmation test, then the fault may be in the
cable.
·
If the reading improves, but is still poor, at the motor, then there may be a fault in both the motor
and cable.
·
If the reading shows similar results at the motor, then the fault exists in the motor.
Rotor Windings
In the case of synchronous motors or generators that have windings in the rotor, if a fault is detected
with the ALL-TEST
PRO®
31, rotate the shaft any amount and retest. If the readings change, or move
with the repositioning of the rotor, then the fault will most likely be found in the rotor windings.
If the readings remain the same then the fault is most likely in the stator.
In addition to the recommendations from the next section
, also see pages 34-35.
Confirming Suspected Winding Shorts
Experience has shown that for most three phases, AC, squirrel cage, inductions motors, 200 Hz are the
best frequency at which to test the condition of the windings. However in some cases, due to the
permeability of the rotor or stator core, the rotor design, air gap, winding configuration or rotor position,
the default frequency may provide a false negative at 200 Hz. However, we have found that if the
winding appears good at any frequency it is generally a good winding.
Note:
The these guidelines are generic and hold true for identifying developing winding shorts for most
applications. However, it may be necessary to compare reading to like motors.