Why rating of motor in KW?

Answer 1

motors are rated in kw why because for motor the load is mechanical load. only active power converted to mechanical power is significant and in motor rotational losses,frictional and windage losses, we cant express these losses in VA, only expressed in KW. hence the motor rating in KW

-ashok(BE)

Answer 2

Because, in most countries, the horsepower is considered obsolete, the output all motors, a.c. or d.c. (and internal combustion engines, come to that!), are expressed in kilowatts . The horsepower is simply the Imperial Unit for power, whereas the watt is the SI unit for power.

Answer 3

Motors are rated in KW only because for motors the load is

mechanical and thus only active power which is converted to

mechanical is significant. The power factor of the motor is

independent of the load and at whatever power-factor it

works it is due to its design

Answer 4

A kW rating tells the amount of useful power the motor can provide. Rating in kV.A could be misleading as a low power factor motor could appear to do more work than a more efficient, lower kV.A (but higher kW) motor.

Answer

The purpose of a motor is to drive a mechanical load, so what matters is the actual power it can supply to that load. Since power is expressed in watts, a motor's output is always is expressed in watts. The motor doesn't supply apparent power(expressed in volt amperes) to the load, so rating a motor's output in volt amperes would be meaningless.

Remember, the power rating of a motor describes its output, not its input, power. In the United States, this is usually expressed in horsepower but, elsewhere, it is expressed in watts. The horsepower is the Imperial Unit for power, whereas the watt is the SI unit for power.

Answer 5

The output of a motor (it's rated power output) must be matched to the mechanical load which it is to drive. This is measured in watts, so it makes sense for the motor's output to be measured in watts. It's also the 'in-phase' component of the motor's current that is responsible for driving the load (the 'quadrature' component supplies the magnetic field); the supply voltage times the in-phase component of the load current is measured in watts.

Answer 6

Motors are rated according to their output power -i.e. the rate at which electrical energy is converted into mechanical energy. Power is expressed in watts. However, in the United States, the Imperial measurement of power, the horsepower, is still widely used.

Answer 7

The rated power of a motor is its output power. Most countries express this in watts, but horsepower is still used in the United States.