Check Insulat ion Resistance (Hermetic M otor)
Test the machine compressor motor and its power lead insulation resistance with a 500-v
insulation tester su c h as a m ego hmmeter. (Use a 5000-v t ester for motors rated ov er 60 0 v.)
Factory-mounted starters do not require a megohm test.
1. Open the starter main dis c o nnect switch and foll ow lo ckout/tagout rules .
2. With the tester connected to the motor leads, take 10-second and 60-second megohm
readings as follows:
6-Lead Motor — T ie all 6 leads together and tes t between the lead group and groun d. Next
tie leads in pairs, 1 an d 4, 2 and 5, and 3 and 6. Test be tween each pair while groun ding the
third pair.
3-Lead Motor — Tie t er m in als 1, 2, and 3 together and test between the group an d gr ou nd.
3. Divide the 60-second r es i stance reading by the 10- s e cond reading. The rat io, or
polarization index, m us t be one or higher. Both the 10- and 60- s ec o nd readings must be at
least 50 megohms.
CAUTION CAUTION
!
If the motor starter is a solid-state start e r, the motor leads must be disconnect ed
from the starter before an insulation test is performed. The voltage generated
from the tester can damage the starter solid-state components.