# Why Electric Motors are Rated in kW and not in kVA?

- Link: https://studyelectrical.com/2016/04/why-electric-motors-are-rated-in-kw-and.html
- Published: 2016-04-21T06:58:00+00:00
- Author: 

![Why%2BElectric%2BMotors%2BRated%2Bin%2BKW](https://3.bp.blogspot.com/-oZfcN9o2vi4/
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Unlike Generators and Transformers, Electric Motors are rated in kW instead of kVA.
We have already discussed [why electric transformers are rated in kVA](http://www.studyelectrical.com/2014/08/why-transformers-are-rated-in-kva-not-in-kw.html).
This article explains why electric motors are rated in kW.

We know that,

kVA = Voltage×Current

kW  = Voltage×Current×Power Factor 

In the case of the [transformer](https://studyelectrical.com/2018/08/practical-transformer-on-no-load.html)
and generator, the designer or manufacturer does not know what is the actual power
factor of the system. It is because while designing a transformer or generator the
designer cannot predict the power factor.

The power factor of an electrical system depends on the nature of the connected 
load ie., inductive, resistive or capacitive. Since the [power factor](https://studyelectrical.com/2016/07/what-is-power-factor.html)
is unknown both generator and transformer are rated in kVA.

But in the case of a motor, it has a fixed power factor. That is why the power factor
is included in the nameplate data. Hence, Electric Motors are rated in kW and not
in kVA.

In addition, Motor is a device which converts electrical power into mechanical power.
In this case, the load is not electrical, but mechanical (Motor’s Output) and we
take into the account only active power which has to be converted into the mechanical
load. Moreover, the motor power factor does not depend on the load and it works 
on any power factor because of its design.

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