400 HP Motor

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Dr.Sparks

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I just got a call from a customer that has been experiencing problems with a 600 HP 5kv Motor. He has had the motor rewound 3 times in the last 6 months due to overloaded windings. I had suggested to him that a soft start may alleviate some of your problems. Well, he had his home office purchase the SS and it appaears as though the wrong voltage was ordered. He now wants me to install a 5kvX480v transformer, soft start and a 400 HP 480V motor. This motor serves a dredge pump that is in a mineral mining operation. I am taking a trip out there this afternoon to look @ what he is trying to do and honestly, I am scared! He is one of my best customers, he pays my invoices the next day, and I get 1 or 2 service calls a week- so I kind of have to do what he wants as long as it is NEC compliant. I know that the engineering on this request is "lacking" and the potential for serious damage to another motor is most likely in the near future. This application is certainly outdoor in a wet location and he needs to have it up and running by Monday morning. I just called 4 of my guys and asked if they wanted overtime and of course they grabbed it. What can you guys think of as far as material for this job. I just don't want to miss anything because the supply houses are only open until noon tomorrow. Any help on this would be greatly appreciated!
 
Dr.Sparks said:
I just got a call from a customer that has been experiencing problems with a 600 HP 5kv Motor. He has had the motor rewound 3 times in the last 6 months due to overloaded windings. I had suggested to him that a soft start may alleviate some of your problems. Well, he had his home office purchase the SS and it appaears as though the wrong voltage was ordered. He now wants me to install a 5kvX480v transformer, soft start and a 400 HP 480V motor. This motor serves a dredge pump that is in a mineral mining operation. I am taking a trip out there this afternoon to look @ what he is trying to do and honestly, I am scared! He is one of my best customers, he pays my invoices the next day, and I get 1 or 2 service calls a week- so I kind of have to do what he wants as long as it is NEC compliant. I know that the engineering on this request is "lacking" and the potential for serious damage to another motor is most likely in the near future. This application is certainly outdoor in a wet location and he needs to have it up and running by Monday morning. I just called 4 of my guys and asked if they wanted overtime and of course they grabbed it. What can you guys think of as far as material for this job. I just don't want to miss anything because the supply houses are only open until noon tomorrow. Any help on this would be greatly appreciated!
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I can understand that you would and probably should be concerned.
If the 600HP motor was cooking its nads off, it seems totally perverse to consider that a 400HP motor would be adequate if it's for the same application.
 
Besoeker said:
I can understand that you would and probably should be concerned.
If the 600HP motor was cooking its nads off, it seems totally perverse to consider that a 400HP motor would be adequate if it's for the same application.
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I couldn't agree more!

Soft starters solve a lot of problems, but they do not create work energy that is not there...

The only possibility is if he throttles down the pump flow to where the motor is only required to deliver 400HP. But if he were able to do that, it would have saved his 600HP motor as well!

This is not an electrical problem in my opinion. Good luck with that.
 
I am assuming it has already been proven that the burned out windings were due to straight up overload and not due to voltage or current unbalance or something else. Was the old motor pulling over nameplate FLA?

If the old motor was just overloaded, then I agree a larger motor is needed to perform the work.
 
I wonder who gave him the idea that replacing an overloaded 600HP motor with a 400HP motor will solve his problem.

maybe the soft starter salesman?

or the guy that sold him the 400HP motor.
 
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weressl said:
One defintion of insanity is; repeatedly doing the same thing, expecting different result.:D
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Good point! Never commit the same mistakes!

More data could be helpful in solving your client's problem. How about pump ratings, liquid being pumped and its specific gravity, actual current draw of previous 600HP motor, etc.. Or maybe a simple throttling can save your 400HP motor.

My 2?.
 
I have a customer that has an Ice plant that was burning up 3 and 4 hundred hp direct drive compressors, 2-3000 amp 480 volt wye services setting side by side, one service did not have a neutral or a ground pulled from the transformer, the other service had only a #4 pulled in with each parallel service lateral. No 277 volt loads on this service, so their was no neutral load. The engineers decided that was the problem, so I pulled out the #4 and pulled in 4/0 in all of the parallel conduits for both services, properly bonded the services to the grounding electrodes. That was a year ago have not heard of them having any more problems. Might check the ground system.
 
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