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a. Open the starter main disconnect switch and follow lockout/tagout rules.
b. With the tester connected to the motor leads, take 10-second and 60-second megohm
readings as follows:
6-Lead Motor
— Tie all 6 leads together and test between the lead group and ground.
Next tie leads in pairs, 1 and 4, 2 and 5, and 3 and 6. Test between each pair while
grounding the third pair.
3-Lead Motor — Tie terminals 1, 2, and 3 together and test between the group and
ground.
c. Divide the 60-second resistance reading by the 10-second reading. The ratio, or
polarization index, must be one or higher. Both the 10- and 60-second readings must be
at least 50 megohms.
If the readings on a field-installed starter are unsatisfactory, repeat the test at the motor
with the power leads disconnected. Satisfactory readings in this second test indicate the
fault is in the power leads.
CAUTION
CAUTION
!
If the motor starter is a solid-state starter, the motor leads must be disconnected
from the starter before an insulation test is performed. The voltage generated
from the tester can damage the starter solid-state components.