Page 162 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

MAINTENANCE OF MOTORS

Acceptance criteria 1000 M 2.0 unless insulation resistance at 1 min 10% if test is performed from motor control center. Resistance 5% if test is performed at motor Min. resistance Max. resistance Average resistance Linear variation between applied voltage and leakage Stable surge waveform while voltage

IR at 20°C IR at 40°C 240 M PI 5000 M is Resistance unbalance unbalance Resistance unbalance current ■ ■

Test purpose Determines insulation resistance Detects contamination, dirt, and humidity in insulation 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 insulatio

Tests and Acceptance Criteria for a 4-kV Motor Test voltage 2500 V dc 2500 V dc 5 V dc at 6 A Maximum voltage 9000 V Peak voltage 9000 V

TABLE 8.4 Test Insulation resistance (IR) Polarization index (PI) Terminal-to-terminal resistances (winding resistances) DC high-potential (hipot) Surge voltage

8.17
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