Why Electrical Motor in KW insted of KVA & Transformer in KVA insted of KW
There are two type of losses in a transformer;
1. Copper Losses
2. Iron Losses or Core Losses or Insulation Losses
Copper losses ( I²R)depends on Current which passing through transformer winding while Iron Losses or Core Losses or Insulation Losses depends on Voltage.
1. Copper Losses
2. Iron Losses or Core Losses or Insulation Losses
Copper losses ( I²R)depends on Current which passing through transformer winding while Iron Losses or Core Losses or Insulation Losses depends on Voltage.
So the Cu Losses depend on the rating current of the load so the load type will determine the powerfactor P.F ,
Thats why the rating of Transformer in kVA,Not in kW.
Designer doesn’t know the actual consumer power factor while
manufacturing transformers and generators i.e. the P.F (Power factor) of
Transformer and Generator/Alternator depends on the nature of connected
load such as resistive load, capacitive load, and inductive load as
Motors, etc.
But
Motor has fixed Power factor, i.e. motor has defined
power factor and the rating has been mentioned in KW on Motor nameplate
data table. That’s why we are rated Motor in kW or HP (kilowatts/
Horsepower) instead of 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 mechanical load. Moreover, the
motor power factor does not depend on the load and it works on any P.F
because of its design