If the readings on a fie ld-installed start er are unsatisfactor y, repeat the test at the motor with
the power leads disconne cted. Satisfacto r y re adi ngs in this second test ind icate the fault is
in the power l eads.
Note: Unit-mounted starters do not have to be megohm test ed.
Check Insulat ion Resistan ce (Open-Dri ve Motor)
Before operating volt ag es is applied to the moto r, whether for checkin g r ot ation direction or
for actual operation, the resistance of the st at or winding insulatio n should be measured.
The test voltage, base d on t he motor operating volt age, is as follows:
This is particularly imp ortant if the motor may hav e be en exposed to excess iv e da mpness
either during transit or whi le in storage. A ‘‘meg ger ’ ’ type instrument can be us e d to measure
the insulation resist an ce. The test voltage s hou ld be applied betwee n th e entire winding (all
winding leads connect ed together) and gro und for approximatel y one minute with th e winding at
ambient tempera ture. The rec ommended minimu m insulation re sistance is d etermined as
follows:
Operating Voltage DC Test Voltage
0- 900 500
901- 7000 1000
7001-14500 2500