ALL-TEST
PRO
®
31 User Manual
©2011, ALL-TEST
Pro,
LLC
www.alltestpro.com
rev 2011-11F
35
3.
Split the fields
– Evenly split the fields and compare the test results. The Fi and I/F readings
should be within one digit of each other.
The DC armature can be evaluated using one of three methods:
1.
Trend
– the overall armature circuit reading is trended over time. The Fi and I/F should not
change more than one digit.
2.
Compare
– Compare the armature results from two similar DC motors (see above) to each other.
The Fi and I/F readings should be within one digit of each other.
3.
Bar to bar testing
– The test results should show as a repeating pattern.
IX. Additional Test Methods
Wound Rotor Motors
When testing a wound rotor motor, the stator coils and rotor coils must be tested separately. The
procedure below must be followed, or results will not be reliable.
When testing the stator coils, the three phases of rotor coils must be shorted together and connected to
an earth ground to “bleed off” circulating currents induced by the stator. Data interpretation rules are the
same as for induction motors as shown on page 29.
Rotor coils are tested through the slip rings. All three stator phases must be shorted together and
grounded. Once again, data interpretation rules are the same as for induction motors as shown on page
29.
Wye-Delta Motors
Wye-Delta motors are often found on large chillers as well as in other applications. They will have six
leads numbered T-1 through T-6, all running to the motor control center. When testing this type of
motor, use the following connection sequence:
Phase 1
T1 to T4
Phase 2
T2 to T5
Phase 3
T3 to T6
Note that testing T1-T2, T1-T3, and T2-T3 will normally show open phases (no continuity).
MegOhm testing should be performed on each of the three phases.
Data interpretation rules are the same as for induction motors as shown for on page 29.
