4pole motor 50Hz

Karsten · Apr 29, 2020

Hi I have an IEC motor 4pole motor 50Hz 5.5kw. It is stamped with 1540rpm. Is this even possible for a 4-pole motor?

AustralIan · Apr 29, 2020

Sounds like you have a 50 Hz 5.5 4 pole generator.

jraef · Apr 29, 2020

... or it is a 1450RPM motor, stamped by someone with dyslexia.

g.mccormick · Apr 29, 2020

jraef said:
... or it is a 1450RPM motor, stamped by someone with dyslexia.

Im with you thinking someone has lysdexia

GaryS · Apr 29, 2020

The base speed on a 4 pole 50Hz motor is 1500 rpm
n = f (2 / p) 60 (1)
where
n = shaft rotation speed (rev/min, rpm)
f = frequency of electrical power supply (Hz, cycles/sec, 1/s)
p = number of poles

so it would not be possible to have run at 1540
but if it is a 60 Hz motor the base speed would 1800 rpm
1540 would be a very high slip motor if it slipped that far it would run very hot
so the numbers don't make sense

AustralIan · Apr 29, 2020

GaryS said:
so the numbers don't make sense

Unless it was a generator.

GaryS · Apr 29, 2020

Not so if its a generator then for a 4 pole it would need to be driven at 1500 rom for 50HZ
and 1800 rpm for 60 HZ
The number of pols, Hz and the RPMs will still be the same weather is a motor or a generator
again the numbers as posted don't make sense it think the numbers got transposed
1540 should be 1450 that would make sense that would be about .05 % slip
or 50rpm slip under load sounds about right

Maxkling · Apr 29, 2020

1540 NL (no load) = 1500 FL (full load)

https://www.allmand.com/content/dam...rt/Athlon Generator_Troubleshooting_Guide.pdf

I wonder if it’s stamped for no slip.

lfe · Apr 29, 2020

An asynchronous induction motor if it acts as a generator will rotate at more r.pm. than the frequency revs.

If it were a synchronous generator it would spin at the exact frequency revs.

But I also think that the one who printed 1540 was wrong.

kamenges · Apr 29, 2020

My guess is going to be induction generator. It will be interesting is Karsten posts again.

Keith

GaryS · Apr 29, 2020

From the manual

60 Hz. - 1850 RPM, NL to 1800 RPM, FL
50 Hz. - 1540 RPM, NL to 1500 RPM, FL
it's a generator not a motor no load RPM 1540 for 50HZ
that 40 rpm slip from no load to full load
the frequency will be a little higher at no load
obviously not intended to line synced

Karsten · Apr 30, 2020

1540rpm

Hi All,

Yes, turns out that is is a generator that shall be run as a motor. The way I see it it is a standard motot respeced.

One thing that is strange is that they specify Locked Rotor Time:
12s(hot)
22s(cold)

I have never seen this specified on a motor why would that be specified here? If running as a motor will it stay in locked rotor state for 12-22s or is that max permissible?

rupej · May 2, 2020

Guessing here, but I would assume that is the max permissible. Seems like a long time but that thing may be a tank.

kamenges · May 2, 2020

Originally posted by Karsten:

I have never seen this specified on a motor why would that be specified here?

If you know how to do it (and I most certainly don't) you can use those two numbers to develop a thermal model of the motor/generator based on a given current through it and an assumed ambient temperature. If you know how it heats up you can figure out how it cools down as well.

Keith

4pole motor 50Hz

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