Ac Machine Loading

[NCT]

Kindly clarify what will happen if a40 kw induction motor runs with no load for asufficient time. What will be the effect on power factor.

 

2. What will happen if a 250 kva alternator is loded with 40 percent load .

[marke]

Hello NCT

 

If you run a motor under no load conditions, it will draw the magnetizing current which is typically 20% - 50% of the current rating of the motor. This is an inductive current and will reduce the plant power factor.

The motor will also draw a small amount of current for the iron loss and also the frictional loss. These losses are pretty small depending on the motor, but can range from around 30% for small motors to 3% for large motors.

The magnetizing current is constant and is independent of the motor load.

Best regards,

[Pragathees...]

Hello NCT,

If you run an induction motor on no load, it will draw more reactive power from grid which will weaken the supply system and of course your power factor will come down and ultimately you have to make excess electricity bill for the same consumption..since the EB bills are charged on KVA basis.. if your power factor is low, your KVA will raise..

 

KW/PF = KVA (Power factor denomination reduces and the KVA increase..)

 

For the generator nothing will happen if you running the set with 40% load of course the efficiency and cost of generation will increase..

 

Pragathees...

 

Kindly clarify what will happen if a40 kw induction motor runs with no load for asufficient time. What will be the effect on power factor.

 

2. What will happen if a 250 kva alternator is loded with 40 percent load .