a.Open the starter main disconnect switch and follow lockout/tagout rules.
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.
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.
