Two speed one winding motor troubleshooting advice

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Ingenieur said:
actually both
'results in' is a better word

the contention was 'only' or 'just' voltage, not accurate
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I see this as controversial as a chicken vs egg coming first debate.

Most will side with the fact that we apply voltage and that will result in current flowing, I think.

The source most will say develops a voltage, whether there is a circuit through a load or not. You get current when you complete a circuit from that source through a load.
 
kwired said:
I see this as controversial as a chicken vs egg coming first debate.

Most will side with the fact that we apply voltage and that will result in current flowing, I think.

The source most will say develops a voltage, whether there is a circuit through a load or not. You get current when you complete a circuit from that source through a load.
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a motor will not function with 'only' or 'just' voltage
most would agree
 
Besoeker said:
The supply PF has no bearing on how the motor performs.
Apply voltage to the motor terminals. It will then draw current at a power factor determined by the motor characteristics at the slip it is operating at.
Just basic Steinmetz after all.
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sure it does
so the source will deliver current? and hence power?, not 'just' or 'only' voltage?

and yet, you have no idea for the 30% I delta
same motor
same voltage
same 0% load
 
Ingenieur said:
a motor will not function with 'only' or 'just' voltage
most would agree
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Correct, but the motor controller is for the most part seen as controlling application of voltage, and current just happens to go along for the ride.

does the source produce current or voltage? I guess you can say both, but can you have one without the other, and if so which one?
 
Shorting contactor

Shorting contactor

I have read through this thread and maybe the difference between the motor shop and field current variance may be from the integrity of the contactor. I would suspect at the motor shop the connections were bolted to achieve the hi speed.
I have experienced with wound rotor motors variations in their performance when the shorting contactor contacts required maintenance/replacement
 
One possibility is it the motor shop was operating closer to 460 volts at the motor or possibly 460 unloaded, where at the site, he has 480 volts and 476 volts at a loaded motor... Maybe closer to 500 at the switchgear or transformer taps.

Redo the calculations just assuming for a moment for humor sake a 44 volt difference in input voltages, 460 vs 504. It seems to me that one would use plus percent taps on large motors with long runs of wire to them to compensate for voltage drop.
 
Ingenieur said:
sure it does
so the source will deliver current? and hence power?, not 'just' or 'only' voltage?

and yet, you have no idea for the 30% I delta
same motor
same voltage
same 0% load
Click to expand...

I'm late to the party here. Are you saying that a poor power factor is the reason the motor is pulling too many amps? i.e. the electricity at the motor shop is good and the electricity at the job site is bad?
 
ActionDave said:
I'm late to the party here. Are you saying that a poor power factor is the reason the motor is pulling too many amps? i.e. the electricity at the motor shop is good and the electricity at the job site is bad?
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Perhaps he is talking about power quality: good (electricity) at shop and poor (electricity) at field?
 
JFletcher said:
One possibility is it the motor shop was operating closer to 460 volts at the motor or possibly 460 unloaded, where at the site, he has 480 volts and 476 volts at a loaded motor... Maybe closer to 500 at the switchgear or transformer taps.

Redo the calculations just assuming for a moment for humor sake a 44 volt difference in input voltages, 460 vs 504. It seems to me that one would use plus percent taps on large motors with long runs of wire to them to compensate for voltage drop.
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we know we have 475 at the motor, as measured
even if the shop is 500 or plus 5% that would only increase current 4-5%, we have a 30% increase

460 vs 504, 10% v increase, ~8-10% I increase, observed is 30%

it runs normal on lo, 80% x rated
it runs high on hi, 115%
on no load it runs 152 vs 195, shop vs field, but we do not know conditions: temp, spec, voltage (should only make a small difference), etc
if damaged it should impact all load conditions

do we evne know if the no load test was done in lo, hi, ???? at the shop

no one has offered a viable option for the 30%
same motor
same voltage ~
same load
 
ActionDave said:
That's what it seems like.
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I agree. But cage induction motors are pretty tolerant of poor quality supplies. I've seen them run fine at a paper mill where the the voltage distortion on the 400V distribution was around 15%, about the worst I've seen anywhere.
 
Besoeker said:
I agree. But cage induction motors are pretty tolerant of poor quality supplies. I've seen them run fine at a paper mill where the the voltage distortion on the 400V distribution was around 15%, about the worst I've seen anywhere.
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then why a 30% delta?
same motor
same v
same load
 
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