Recent content by jmcs

I have a pump circuit that has 2 sets of lightning arrestors and 2 sets of surge capacitors on it. Does anyone have any information on whether or not the 2 sets could limit the effectiveness or interfere with the proper operation of one or both sets?

Thanks for pointing out article 110-3 "approved". I have used the NO contact for PLC monitoring in the past on new installations but this is a older MCC with only NC contacts. I could also install a interposing relay to give me a NO and NC. I'm curious as to the scheme with overload...

Wbd, Thanks for your comments, I feel the same way. I thought maybe it was a NEMA standard or maybe the NFPA would have something dealing with the wiring practices for overloads, but I can't seem to find it.

Is anyone aware of a code or standard that says a motor overload relay must be hard wired to the coil of the starter. The only thing I can find in the NEC referencing the wiring allows the overload device to be wired to a supervised alarm when an imediate shutdown of the motor would create a...

dougantholz, Thanks for the advice. I've hired a contractor who is using a structural engineer who owes him a favor to size the beam, support spacing, footings required, etc. I was wanting to double check his work if there was some way of doing it without to much trouble. Since I don't know the...

We're remodeling our basement and I'm looking for information on how to size a beam so that we can get rid of some or all of the poles supporting the existing beam. Does anyone know of a software package or literature that could help? Thanks, Jeff

The information I'm looking for would be a chart of the temperature rise and long term effects on the motor insulation of a motor running with a voltage imbalance of .9 to 1.1 percent and current of about 5 percent. I have a customer that has had several motor failures in the past two years...

Thanks for the links. I'll try them.

Has anyone had time to look at the bitmaps or jpegs and if so what is your opinion on the cause of motor failure? Am I trying to make something of nothing or could all of these disturbances combined be related to the motor failures? Thanks, Jeff

dynets, Renting a 3 phase protective relay test set would allow you to test the unbalance relay all day without damaging a motor.

electricpete, What is your opinion of the power analyzer data? jbartos, Thanks for the qreat links chrishart, The softstart was installed by a contractor to solve the problem. There have not been any motor failures since,but it's only been about 7 weeks. I don't believe it is the solution...

rhatcher, Thanks for the link. electricpete, I've e-mailed you the bitmaps. Let me know what you think. I've got alot more of them but I think there is a example of most accurrences included in what I sent. The 50 hp motor is 3 phase. Every 30 to 40 minutes the voltage dips because of the 50 hp...

Electricpete, The motor is a 100 hp deep well submersable pump. When the voltage dips as a result of the 50 hp starting the current also dips, but then increases slightly over typical running current then back to typical, which is oscillating. I thought the oscillations were possibly load...

Electricpete, Thanks for the info. Something strange about the current imbalance, it exists even when the voltage is perfectly balanced. Any thoughts? I would like the formula. Thanks

The information I'm looking for would be a chart of the temperature rise and long term effects on the motor insulation of a motor running with a voltage imbalance of .9 to 1.1 percent and current of about 5 percent. I have a customer that has had several motor failures in the past two years...