Two speed one winding motor troubleshooting advice

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So let me ask this, because I’m not sure how to measure it and what the consequences would be. Maybe you guys do?

In high speed we are bringing back the T1, T2, and T3 connections, with #2 wire that has read too hot on IR scans dating back to 2002, and shorting these three wires together. Now at the starter end how do we measure what the voltage drop on these #2 conductors are? If it is found to be excessive what symptoms will be displayed? If allowed to go on long enough what harm may happen?

Seems to me best we can do is compare currents. T1 and T6 should have the same current, correct? The degree of imbalance would only be attributable to difference in winding and/wiring impedance, correct? Trying to wrap my head around if both currents should sum to zero even.
 
shop vs field
same motor
~same v, >460 rating
same load, ~0%
as some say pf has no bearing
no apparent damage as lo speed is fine, and i is balanced at 0% and 115%
we do not know operating temps, but unlikely to increase i by 30%

so what could possibly account for the delta?
no seems willing to venture a guess
 
Russs57 said:
So let me ask this, because I’m not sure how to measure it and what the consequences would be. Maybe you guys do?

In high speed we are bringing back the T1, T2, and T3 connections, with #2 wire that has read too hot on IR scans dating back to 2002, and shorting these three wires together. Now at the starter end how do we measure what the voltage drop on these #2 conductors are? If it is found to be excessive what symptoms will be displayed? If allowed to go on long enough what harm may happen?

Seems to me best we can do is compare currents. T1 and T6 should have the same current, correct? The degree of imbalance would only be attributable to difference in winding and/wiring impedance, correct? Trying to wrap my head around if both currents should sum to zero even.
Click to expand...

each wye must sum to 0
the wyes are not common/bonded to each other
one is permanent made at the motor
the other via the #2 by contactors 110' away
this may lead to a few % i imbalance per coil pair
I wonder of connecting the 2 wye centers would matter?
doubt it, better balance, but it's not bad as is

I calc'ed the #2 drop, less than 5 v plus another 2 from the 500's
less than 2% and about 470 at the motor
he measured 274 but this does not factor in the #2 drop

his wye i at contactor is ~158 avg (via the #2)
his fla is 327 avg
if perfect balance ~163
his are 158 and (327-158) = 169
158/327 = >48%, the other <52%, does not seem like an issue
the contactor wye has the 110' of #2 so you would expect it to be a bit lower

imo no wiring issues
the motor was checked
what does that leave?
 
phineascage said:
Thank you Sir. I believe it's going to be sent out again anyway whether we really want to or not as it's getting hot enough to cook eggs on. It's also producing that old familiar burnt winding smell.
Click to expand...
Have you considered some aux cooling to get you by until it can be taken out of service? Additional cooling can forgive a multitude of sins...for a little while anyway.
 
Ingenieur said:
yep
lo they are in series you have 8 poles
in hi they are paralleled, ie, you pair up poles (ie by phase) so result is 4

in the basic diagram each coil is actually 4 pole pairs (8 poles)
that is cut in half when paralleled
Click to expand...
How is this motor wound in comparison to a typical 9 lead dual voltage motor? No way you change the number of poles in those when you configure in two parallel wye's for low voltage operation, if you did you wouldn't have same speed at high/low voltage.
 
Ingenieur said:
it consumes power, actually converts
the i that enters = the i that leaves, kcl, which means no i is 'consumed'
as you know
Click to expand...
OK. Motor receives just voltage. It is just another connected load to a common voltage supply. The supply power factor is not an issue.
 
kwired said:
All the drawings so far are showing same coils just connected in different manners, still using all of the coils in all the different configurations, how does that change number of poles?

Change in number of poles would definitely change speed but that isn't what we have here. All we are doing here is changing voltage applied across each coil and therefore not producing as much torque in some configurations as others, which results in more slip.
Click to expand...

Have a look at these pages for a basic explanation.

https://en.wikipedia.org/wiki/Dahlander_pole_changing_motor

http://machineryequipmentonline.com...ole-motorsthree-speed-consequent-pole-motors/

CONSEQUENT-POLE-MOTORS-0884.jpg

MTW
 
Besoeker said:
OK. Motor receives just voltage. It is just another connected load to a common voltage supply. The supply power factor is not an issue.
Click to expand...

no it doesn.t
receives v, I at a pfa and their product power, both active and reactive


please explain:
same motor, no apparent damage
a day apart it measures 30% more 0% load current site vs shop
same v, pf has no effect

what caused the difference?
what other possible cause could there be? just speculate, you are allowed and do it frequently (we all do)
I have no plausible explanation

here's the issue: we are electrical guys, we assume no other possibility
imo the issue is external to the motor and is not electrical in nature
lo I<rated and balanced
hi I>rated and balanced
0% load, balanced, we do not know what rated is, with the nameplate we could know, for all we know the shop used pf correction in their test set-up
 
kwired said:
How is this motor wound in comparison to a typical 9 lead dual voltage motor? No way you change the number of poles in those when you configure in two parallel wye's for low voltage operation, if you did you wouldn't have same speed at high/low voltage.
Click to expand...

wiki version aka pole changing motor https://en.wikipedia.org/wiki/Dahlander_pole_changing_motor

Fitzgerald machinery text 11.3.1 Pole Changing Motors, excerpts attached
 

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Ingenieur said:
no it doesn.t
receives v, I at a pfa and their product power, both active and reactive
Click to expand...

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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