Power factor of 3MW Induction Motor 1

[Paulpower]

Hello everyone,

Generally, PF of induction motor rated 50KW or below is 0.8 - 0.85, but can I specify the PF of a 2MW - 3MW induction motor as 0.9 or higher?

Does any manufacturer catalogue cover this information?

Thanks,

Paulpower

 

[ScottyUK]

As machine speed drops and the number of poles increases the power factor generally worsens. The value you're using isn't a bad guess for a 4-pole machine but will be hopelessly optimistic for (say) a 12-pole machine.

If you need a good power factor, especially on a big machine like that, then specify a synchronous motor. You can set its excitation to be VAr-neutral or use it to compensate for other lagging loads on the same bus by over-exciting it.


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[jraef]

Listen to ScottyUK; great advice.

I'll only add the following:

Does any manufacturer catalogue cover this information?

Generally, a motor that big is custom built to order, so it's not likely that there are any MV motor catalogs out there with anything other than general features and manufacturing principals in it. To a certain extent, you may even be able to specify what you would like in that regard and someone can probably build it to suit. I have seen .9 pf on 4 pole motors that big.


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[LionelHutz]

I'll just add that I wouldn't expect power factor to go much above 0.9 on any induction motor even if it is large. You are asking if it could be 0.9 or higher. I would figure on 0.88 to 0.90 for a large 2 or 4 pole motor.

 

[dpc]

You should be MUCH more concerned about other motor parameters, especially efficiency. There is a tradeoff between high efficiency and power factor. Power factor can be dealt with via capacitor correction. There is no way to mitigate motor losses after you buy the machine.

As Scotty said, you might want to consider a synchronous machine if you're really concerned about pf.

 

[edison123]

The maximum pf I have seen in motors of that range is only 0.87.

A 0.9 pf would imply a smaller air-gap, which may be ruled out by mechanical considerations like sag, thermal expansion etc.

I agree with dpc that efficiency is more important than pf in a motor since pf correction techniques are available.