Issues with new high eff motor.

JeffKiper

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Long winded story look at the bottom line if you are short on time.

OK I got a call from the local motor shop. They sold a 125 hp to replace a 100 hp about a month ago. The system will run under a load no problem. Every now and then the system will shutdown with a fault. The plant guys just reset the fault without looking at what it was.

I started trouble shooting first looked for mechanical issues. The bearings where 100~116 degrees F. I could turn the load by hand no problem. So I started looking at the controls. This system has a Westinghouse reduced voltage motor starter. I used a the only amp probe I had with me that was a 300A on startup we pegged the full scale. Once the system was up to speed just turning a flywheel the current was 45A. The wave forms looked like a nice 60Hz clean wave, 479VAC on all legs. All looked OK

Then the circuit board LED blinked and the voltage dropped to 230 and the wave form started jumping around. The wave form had some huge spikes in them from 60~90 Hz. in a random pattern like noise. The current went from 45A to 25A. I was at a loss the system looked like it just nosed dived.

I call technical support and the first question was how new is the motor and when did the problem start? I it a permium eff motor? I said yes premium and 1 month old. "turn the second DIP switch OFF on the thirs bank of switches" is what the tech told me to do. It is the energy saving mode. They reduce voltage after 10sec of light load. "These new motors are giving us problems with the old starters, a standard eff. motor will run no problem in our systems" was another comment he tossed out.


Look here if you jumped around the long details.

Has anybody has issues with the Premium Eff motors and older drives or starters causing problems?
 
Is this Westinghouse Reduced Voltage Starter, a softstarter with SCRs or IGBTs? I am (perhaps wrongfully) assuming it's not a Wye-Delta starter so correct me if I am wrong.
 
Last edited:
Why the change from 100 to 125 HP?
What is system - flywheel with 125 HP indicates punch press or other high force impact type.

OK so mechanism is free - construe no mechanical problems.

45 amp with just flywheel up to speed sounds about right. What happens when clutch engages?

Westinghouse tech said
"turn the second DIP switch OFF on the third bank of switches"
Did you? What were results?

Bit confused - are you reporting incident OR looking for help?

Dan Bentler
 
Paul it is a SCR starter. No Wye delta on this one.

Dan the 125 was in stock, so the motir supply house sold it to the. You know how that goes. "I got a 125 on the shelf, or you can wait for the rebuild".
This is on a rotary grinder for PVC pipe. I would guess about a 1000 lbs. drum. "Flywheel" was not the best word for the application. (I was a punch press guy for a long time, old habits die hard"

I did turn off the DIP switch and the voltage jumped back up to 480 and the current went back to 45 Amps. The wave form went back to 60hz and stopped spiking. The system is running OK I ASSuME because my phone hasn't rang today.

It was a problem. Hopefully it is gone. My question is has anybody else has problems with the Premium Eff motors on older drives. It sounded fishy to me that the new motors cause problems with a Soft starter. I could see a sensorless vector drive where the motor model didn't match the motor. Because the drive was made well before the Premium eff. motors where out.
 
The issue is not that the starter was older but that it was using the energy saving mode feature.
The energy saving feature is found on some Solid State Starters, both new and old. It is mostly a sales gimmick which gives little actual energy savings in most applications. The theory is that if the motor is lightly loaded, the voltage to the motor can be reduced, which causes a reduction in current, and energy can be saved. The way the starter reduces the voltage is by not turning the SCRs on for a full 1/2 cycle. With the new motor, the starter control must have become unstable and caused the unstable waveform. It is not unusual to have problems with the energy saver and most of the time they are left disabled. It was probably just a fluke that the old motor didn't have problems in the energy saving mode.

See this link for more information on energy savers.
 

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