Page 161 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

MAINTENANCE OF MOTORS

Acceptance criteria Resistance unbalance 10% if test is performed from motor control center. Resistance 5% if test is performed at motor. Min.resistance Average resistance Linear variation between applied voltage and Stable surge waveform while voltage is increasing Identical waveform for all three phases

IR at 20°C 40 M IR at 40°C 10 M unbalance Resistance unbalance Max. resistance leakage current ■ ■

Test purpose Determines insulation resistance Identifies short circuits, open circuits, ground faults, phase-to-phase faults, loose connec- tions, dirt accumulation at connections, etc. Nondestructive evaluation of dielectric strength of groundwall insulation (slot liner) Identifies interturn faults, phase-to-p

Tests and Acceptance Criteria for a 575-V Motor Test voltage 1000 V dc 5 V dc at 6 A Maximum voltage 2200 V Peak voltage 2200 V

TABLE 8.3 Test Insulation resistance (IR) Terminal-to-terminal resistances (winding resistances) DC high-potential (hipot) Surge voltage

8.16
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