Ok, so now that I'm the delta 3P expert around here, after thrashing with the 240D, I got suckered into assisting maintenance with the old freight elevator for the complex (vintage 1920). The maintenance guys are pretty darned good mechanically, but they leave the electrical to me 
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Power feed to the machine room is from a 400A 480D entrance via a 100A fused disconnect switch (nothing else on the entrance). Load consists of the original contactor board (rated 440V per nameplate), a small 1P 480-240 transformer powering the safety interlocks, and the motor (rated 50HP, 440V, 68A). The issues I've been chasing are variations in timing behavior in the added in safety circuit relays and the odd catastrophic failure of contactor windings.
What I'm observing from the 480D is what look to me like wild voltage swings from 440V to 510V with the equipment idle. Is this normal behavior for the delta service? I don't observe any of the 240D entrances doing this. I'm considering that voltages 70V above the rating plate of 440V are causing the contactor winding failures and the large swings are messing with the relay timings. Any advice on how to stabilize this?
Vern
.Power feed to the machine room is from a 400A 480D entrance via a 100A fused disconnect switch (nothing else on the entrance). Load consists of the original contactor board (rated 440V per nameplate), a small 1P 480-240 transformer powering the safety interlocks, and the motor (rated 50HP, 440V, 68A). The issues I've been chasing are variations in timing behavior in the added in safety circuit relays and the odd catastrophic failure of contactor windings.
What I'm observing from the 480D is what look to me like wild voltage swings from 440V to 510V with the equipment idle. Is this normal behavior for the delta service? I don't observe any of the 240D entrances doing this. I'm considering that voltages 70V above the rating plate of 440V are causing the contactor winding failures and the large swings are messing with the relay timings. Any advice on how to stabilize this?
Vern
