Two speed one winding motor troubleshooting advice

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Besoeker said:
That's the $64,000 question.
But it isn't site power factor. I thought you might have known that.
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it can only be site pf or load
I thought you could have deduced that

what are some possibilities for the change other than pf and load?
what is the primary factor for unloaded i magnitude for a given motor?

|i| = sqrt((i cos pfa)^2 + (i sin pfa)^2)
if the pfa and i cos pfa are the same for both how can |i| differ?
 
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Ingenieur said:
it can only be site pf or load
I thought you could have deduced that
Click to expand...
It is neither site power factor nor load.
Motor power factor does not depend of site power factor. The reverse is often true. Site power factor, especially on industrial sites, is often affected by the power factor of connected motor loads.
And, if as stated several times, the motor is uncoupled and the current disparity is still there, it isn't load related.

Go in peace.
 
I would imagine you fine gentlemen know this but it bears mentioning as this motor isn’t wound in the normal manner. Any analysis should be based on the motor being an 8 pole motor in low speed and a 4 pole motor in high speed. That isn’t always clear from a schematic of the windings.

If I was forced to guess I’d suspect the #2 wire (and possibly starter) is undersized when operated in high speed. I wonder if prolonged operation could cause rotor damage. I’d be curious to see results if T1, T2, and T3 were bonded together at motor.

Also used to seeing a 5 pole starter used and that makes me wonder if we are looking at a home engineered conversion/solution.
 
Russs57 said:
I would imagine you fine gentlemen know this but it bears mentioning as this motor isn’t wound in the normal manner. Any analysis should be based on the motor being an 8 pole motor in low speed and a 4 pole motor in high speed. That isn’t always clear from a schematic of the windings.

If I was forced to guess I’d suspect the #2 wire (and possibly starter) is undersized when operated in high speed. I wonder if prolonged operation could cause rotor damage. I’d be curious to see results if T1, T2, and T3 were bonded together at motor.

Also used to seeing a 5 pole starter used and that makes me wonder if we are looking at a home engineered conversion/solution.
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The other motors of the same rating work OK.
 
Russs57 said:
I would imagine you fine gentlemen know this but it bears mentioning as this motor isn’t wound in the normal manner. Any analysis should be based on the motor being an 8 pole motor in low speed and a 4 pole motor in high speed. That isn’t always clear from a schematic of the windings.

If I was forced to guess I’d suspect the #2 wire (and possibly starter) is undersized when operated in high speed. I wonder if prolonged operation could cause rotor damage. I’d be curious to see results if T1, T2, and T3 were bonded together at motor.

Also used to seeing a 5 pole starter used and that makes me wonder if we are looking at a home engineered conversion/solution.
Click to expand...

only impacts the speed/power/torque

the v drop is not an issue
as calculated only ~5.2 v or <1.5% and confirmed by your measurements
475 range on a 460 rated motor
the #2 ampacity is an issue but the run is short so little impact on v drop

operating at 414 would only increase i by 8-10%
 
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Ingenieur said:
it can only be site pf or load
I thought you could have deduced that

what are some possibilities for the change other than pf and load?
what is the primary factor for unloaded i magnitude for a given motor?

|i| = sqrt((i cos pfa)^2 + (i sin pfa)^2)
if the pfa and i cos pfa are the same for both how can |i| differ?
Click to expand...

And I would say air gap, flux density, number of poles, and horsepower of motor are far more important. But then I don’t have PE after my name so who cares.
 
has alignment been checked?

the 0 load reading can't tell you anything unless you know pf, v, etc under which they were taken

you lo speed i is ok ~90% rated
the hi is 115%
the good motor is >95%

what are the ol's set at? must be >115%
was this adjusted after the motor was returned?
all motors set the same?
 
Not looking for a pissing match.

Flux density has a lot to do with no load amps. Some motors are operated close to the knee. No load amps is an important test of any motor repair. A typical 4 pole motor might draw around 33% of FLA yet some 10 pole motors might draw 110% of FLA.

But yes, in general I don’t pay to much attention to no load amps. In this case I do think they provide useful info though. We can agree to disagree on this matter.

Time will tell. Let’s see what is discovered. Maybe all of us will gain some knowledge. That is always a good thing.

And I will say just because something has done okay with a bad initial situation doesn’t mean all of the same things will tolerate it over enough time.
 
Russs57 said:
Not looking for a pissing match.

Flux density has a lot to do with no load amps. Some motors are operated close to the knee. No load amps is an important test of any motor repair. A typical 4 pole motor might draw around 33% of FLA yet some 10 pole motors might draw 110% of FLA.

But yes, in general I don’t pay to much attention to no load amps. In this case I do think they provide useful info though. We can agree to disagree on this matter.

Time will tell. Let’s see what is discovered. Maybe all of us will gain some knowledge. That is always a good thing.

And I will say just because something has done okay with a bad initial situation doesn’t mean all of the same things will tolerate it over enough time.
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same motor (not different types)
same 0% load
same v
same ~ P, ie losses
yet 30% more i

the only variable is power factor
unless the motor windings/iron changed between the shop and site
which would change inductance
and pf ~ arctan(inductive reactance/resistance) or arctan(x/r ratio)

what else would provide the change?
something quantifiable had to change


post the nameplate
where are the ol's set?
why was the motor sent out?
who aligned it? and how?
 
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By chance have you confused me with the original poster? I have no info on nameplate, OL settings, alignment, etc.

Only thing we know for certain is this motor draws roughly 45 amps more (25%-30%), on-site, than when tested in shop, in unloaded state. It also draws roughly 45 amps more than other of the identical motors under load on-site.

We don’t have much info on the other motors and are assuming wire sizes and motor starters are the same. It was mentioned problem motor has splices in wiring and we don’t know if other motors do. If anything I think we could safely say all three of the on-site motors are receiving the same power factor. There is little else we can say with certainty.
 
Russs57 said:
By chance have you confused me with the original poster? I have no info on nameplate, OL settings, alignment, etc.

Only thing we know for certain is this motor draws roughly 45 amps more (25%-30%), on-site, than when tested in shop, in unloaded state. It also draws roughly 45 amps more than other of the identical motors under load on-site.

We don’t have much info on the other motors and are assuming wire sizes and motor starters are the same. It was mentioned problem motor has splices in wiring and we don’t know if other motors do. If anything I think we could safely say all three of the on-site motors are receiving the same power factor. There is little else we can say with certainty.
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The motors receive voltage, not power factor. Despite what others may tell you.
 
Besoeker said:
It is neither site power factor nor load.
Motor power factor does not depend of site power factor. The reverse is often true. Site power factor, especially on industrial sites, is often affected by the power factor of connected motor loads.
And, if as stated several times, the motor is uncoupled and the current disparity is still there, it isn't load related.

Go in peace.
Click to expand...
I agree. Power factor is additional current exchanged between the motor and the source, unless you place a PFC capacitor sized to the need somewhere closer to the motor - then that additional current is exchanged between the motor and the PFC, which is a reason for doing so- to keep that additional current off the feeders and service conductors, or even a portion of the branch circuit conductors. Motor still has same PF even if PFC is right next to the motor.
 
Russs57 said:
I would imagine you fine gentlemen know this but it bears mentioning as this motor isn’t wound in the normal manner. Any analysis should be based on the motor being an 8 pole motor in low speed and a 4 pole motor in high speed. That isn’t always clear from a schematic of the windings.

If I was forced to guess I’d suspect the #2 wire (and possibly starter) is undersized when operated in high speed. I wonder if prolonged operation could cause rotor damage. I’d be curious to see results if T1, T2, and T3 were bonded together at motor.

Also used to seeing a 5 pole starter used and that makes me wonder if we are looking at a home engineered conversion/solution.
Click to expand...

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.
 
Russs57 said:
Kwired, perhaps the following link will help. As mentioned the way the motor operates isn't clear from the wiring schematic.

http://www.industrial-electronics.com/Motor_Control_6-32.html
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Where are the illustrations it mentions?

I tried clicking on a link on that page that I thought might show me one and next thing I know I am looking at what appeared to be an attempt at something taking over my computer, luckily was able to close what was opened and things seem to be OK. :blink:
 
Sorry kwired, just pasted first link I saw. Never clicked on anything there. Didn’t want you to take my word on how said motor works.

I’ll make a stab. In low speed you have two windings in series with the T4, T5, T6 connections at midpoint. Think of the windings arranged so that the series connection generates four north poles. In between these north poles, four south poles are “induced”, giving you an eight pole motor. In high speed, power is applied at midpoint, so current flows in opposite direction in one pair of the windings. This gives the normal four pole configuration of north, south, north, south poles. The connections are Y/YY.

Best I can do for a quick explanation. A motor rewind guy would probably be your best resource to gain a more in-depth explanation.
 
Russs57 said:
By chance have you confused me with the original poster? I have no info on nameplate, OL settings, alignment, etc.

Only thing we know for certain is this motor draws roughly 45 amps more (25%-30%), on-site, than when tested in shop, in unloaded state. It also draws roughly 45 amps more than other of the identical motors under load on-site.

We don’t have much info on the other motors and are assuming wire sizes and motor starters are the same. It was mentioned problem motor has splices in wiring and we don’t know if other motors do. If anything I think we could safely say all three of the on-site motors are receiving the same power factor. There is little else we can say with certainty.
Click to expand...
I mistook you for the op, sorry
what we don't know is what was the pf when shop tested?

we know
v is ok, even with the #2, > 470 running <2%, 460 rated motor, no issue
lo: it is running below rated i
hi: +15% fla
no load: +30%, vs shop test, no spec sheet

if a damaged or shorted winding I would guess lo would be between +15 and +30% fla
it is actually -20%
the same coils are used for both lo and hi, lo series, hi paralleled
so any damage should be present in lo
the fact that all 3 ph are consistent would imo rule out damage, unlikely that all are damaged to the same degree

hopefully we get feedback
I know what I would do
swap with a 'good' motor
if it reacts the same, likely mech tower issue
if it does not, and the 'bad' motor reads hi on the other tower, motor rebuild time
 
Russs57 said:
Sorry kwired, just pasted first link I saw. Never clicked on anything there. Didn’t want you to take my word on how said motor works.

I’ll make a stab. In low speed you have two windings in series with the T4, T5, T6 connections at midpoint. Think of the windings arranged so that the series connection generates four north poles. In between these north poles, four south poles are “induced”, giving you an eight pole motor. In high speed, power is applied at midpoint, so current flows in opposite direction in one pair of the windings. This gives the normal four pole configuration of north, south, north, south poles. The connections are Y/YY.

Best I can do for a quick explanation. A motor rewind guy would probably be your best resource to gain a more in-depth explanation.
Click to expand...

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
 
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