Amps to kW formula is used to calculate the active power of systems from the known current and voltage values.
Generally, the active power of any system is measured in terms of voltage times the current. The SI unit of voltage is volts whereas current is measured in amps. Hence the unit volt * amps = watts is used. However, the watts is a very small unit and kW is used instead. Four different formulas are used to calculate kW from amps:
DC amps to kW
It is simple fraction of voltage times current divided by 1000.
Example 1: A 240-volt dc motor draws 50 amps current. Find the kW.
Solution: kW = [240 * 50] / 1000 = 12 kW
Single phase amps to kW
It is voltage times current and power factor divided by 1000.
Example 2: A 90-volt single phase universal motor draws 10 amps and power factor 0.8. Calculate the amps.
Solution: kW = [90 * 10 * 0.8] / 1000 = 0.72 kW
Two-phase amps to kW
It is exactly similar to the previous case with the exception that 2 is multiplied in the numerator due to 2 phase system.
Example 3: A 200 V, 2 phase circuit has 3 A current flowing through it. Find the wattage rating of the circuit. The power factor is known to be 0.9.
Solution: kW = [200 * 3 * 2 ] / 1000 = 1.2 kW
Three-phase amps to kW
It is similar to the single phase formula, however, the numerator is multiplied by the factor 1.73. The factor 1.73 actually represents √3 which should be added to the 3 ø calculations.
Example 3: A 400 V, 3 phase induction motor has 5 A current flowing through it. Find the wattage rating of the circuit. The power factor is 88%.
Solution: kW = [400 * 3 * 1.732] / 1000 = 2.07 kW