68. Normal system voltage available, but no voltage at contactor coil when start

Question

68. Normal system voltage available, but no voltage at contactor coil when start/run button is pushed. 69. Motor starts and runs normally, current and voltage to it are normal when measured, but motor occasionally trips its OLs. 70. Motor is completely dead, OLs not tripped. 71. Shaft does not turn at all, motor makes load noise, quickly trips OLs. 72. Circuit breaker trips as soon as motor is switched on. 73. Motor runs slow, heats up, trips OLs. A. Motor ventilation restricted. B. low supply voltage C. Short in motor windings. D. High inertia load. E. Out-of-balance rotor. F. Tripped circuit breaker or blown fuse. G. Intermittent problem in motor or load. H. Short in lines to starter. I. Motor or load jammed. J. Control circuit fuse blown.

Explanation / Answer

68)F tripped circuit breaker or blown fuse

69)G intermittent problem in motor or load

70)J control circuit fuse blown

71)D high inertia load

72)C short in motor windings

73)E out of balance rotor

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