To understand the relation between horse power, kilo watt and kilo volt ampere, we need to know their definitions.
1) Horse power ( hp ) – It is unit to measure the mechanical power. The rate at which the work is done is measured in terms of horsepower.
2) kilo-Volt-Ampere ( kVA ) – It is known as an apparent power of an electric circuit. It is the unit to measure the rate of power in the Electric circuit. It is the product of the voltage and current values in the electric circuit.
3) Kilo-watt ( kW ) – It is the unit for measuring the actual power in an electric circuit. It is also called as useful power or active power of the system.
The value of kVA is equal to kW in DC voltage devices because the current and voltage of the circuit are in the same phase. Whereas in AC voltage devices, due to the power factor of the electrical devices kVA is greater than kW.
Power factor – It is the ratio between the resistance of the circuit and the impedance of the circuit. If the resistance and the impedance of the circuit is the same, power factor becomes 1 which is for a purely resistive circuit. The ratio between the power that can be used and the apparent power of the particular device. Value of power factor may vary from 0 to 1. It depends upon the construction and the components used in an electrical device.. For example, the power factor is 0.6 in electric motor while in some other devices the power factor may be more or less. The circuit is more efficient if the power factor is more because more power can be utilized in the circuit.
Conversion of kilo-Volt-Ampere ( kVA ) to Horsepower ( hp )
For converting kVA to horsepower we need to know the power factor of the electronic device.
As we know, 1 hp = 746 W = 0.746 kW.
So, 1 kVA = kW/(power factor)
1 kVA =1 x ( power factor)/0.746 hp
1) For electric motor, the power factor is considered as 0.6.
1 kVA =1 x 0.6/0.746 hp = 0.804 hp
Let us consider an electric motor which is having a power of 3 kVA. Here we can convert it from kilo volt ampere ( kVA ) to horse power ( hp ) by using the above formula.
As we know, 1 kVA = 0.804 hp
Therefore, 3 kVA = 3 x 0.804 = 2.412 hp
2) for other electronic devices power factor may vary.
Let us consider an electronic device which is having a power of 5 kVA and having a power factor as 0.8. Here we can convert it from kilo volt ampere ( kVA ) to horse power ( hp ) by using the same formula.
Therefore 1 kVA = 1 x ( power factor)/0.746= (0.8 )/0.746= 1.0723 hp
Hence , 5 kVA = 5 x 1.0723 = 5.362 hp
This is how we can calculate the value of horse power for any electrical device by understanding the relation of kilo volt ampere and horse power.
Due to power factor, the values of horsepower may vary depending upon the circuit. There are many loads acting in the circuit. The factors due to which power factor becomes less is the load acting on it such as inductive load, linear load , capacitive load etc.
|Kilo volt ampere ( kVA )||
Horsepower ( hp )
( at power factor = 0.6 )
Horsepower ( hp )
( at power factor = 0.8 )
How can we improve the power factor of the electrical sytem?