ALL-TEST
PRO
®
31 User Manual
©2011, ALL-TEST
Pro,
LLC
www.alltestpro.com
rev 2011-11F
31
If the winding test indicated a developing winding short, based upon an unbalance in phase angle (Fi)
and/or Current Frequency Response (I/F) and:
1.
Impedance is balanced (<3% from average) then a variable frequency test should be
performed. (See variable frequency test below)
2.
Impedance is unbalanced (>3% from average) then a rotor compensated test should be
performed. (See rotor compensation test below)
The test results, such as those found in Table 4, indicate a potential winding fault as Fi is out by more
than 1 from average:
Table 4: Sample Test Results
T1-T2 T1-T3 T2-T3
Fi
66
67
69
I/F
-44
-44
-45
Method 1: Rotor Compensation
Note:
This test
was developed for the ALL-TEST Pro kit using the ALL-TEST
PRO
IV™. Using the
ALL-TEST PRO® 31 & the ALL-TEST PRO IV™ together is the best method available for simply and
accurately determining the condition of the windings in AC 3 phase induction motors.
One of the reasons for the result shown in Table 4 may be a rotor position or a rotor anomaly, such as
severe casting voids, rotor eccentricity, etc. To separate a rotor fault from a winding fault it is necessary
to perform a rotor compensation. Use the procedure listed below to perform the rotor compensation test:
1.
With the Instrument test leads connected to T1 & T2. From display screen 1, turn shaft until
the maximum impedance value is obtained.
2.
Read and record the impedance and phase angle reading from display screen 1.
3.
Depress the TEST key to read and record the I/F value.
4.
Move the Test leads to T1 & T3, turn the shaft until the maximum impedance value is
obtained on this phase.
5.
Read and record the impedance and phase angle reading from display screen 1.
6.
Depress the TEST key to read and record the I/F value.
7.
Move the Test leads to T2 & T3, turn the shaft until the maximum impedance value is
obtained on this phase.
8.
Read and record the impedance and phase angle reading from display screen 1.
9.
Depress the TEST key to read and record the I/F value.
The results should be +/- 1 digit from the average, and the I/F values should be within +/- 2
units from average.
Method 2: Variable Frequency Test
The variable frequency test is used to confirm winding faults if the impedance readings are balanced. It
is recommended to test the winding at 400 Hz, 100Hz, 50 Hz and 25 Hz. If it tests “good” at any of
