HP to Amps formulas are used to calculate current provided that HP (horsepower) is known in any circuit. Given below are the formulas:
|HP to Amps||Formula|
|In case of DC||(HP x 746)/(E x %Efficiency)|
|Single phase AC||(HP x 746)/(E x %Efficiency x PF)|
|Two phase four wire||(HP x 746)/(E x %Efficiency x PF x 2)|
|Three phase||(HP x 746)/(E x %Efficiency x PF x 1.73)|
Example: How much current a 0.5 HP DC motor having efficiency rating of 95% will draw at rated voltage of 12 volts.
Solution: I (DC) = (0.5 * 746) / (12 volts * 0.95)
I (DC) = 32.7
Single Phase AC Circuit
Example: A single phase 1/2 HP, 120 volt AC motor has efficiency rating of 90%. Find the current drawing by motor at power factor of 85%.
Solution: I (Single phase AC) = (0.5 * 746)/(120 * 0.9 * 0.85)
I (Single phase AC) = 4.06 Amps
Two phase four wire system
Example: Determine the current drawn by a two phase 1 HP, 230-volt motor having an efficiency rating of 90% and a power factor of 83%
Solution: I (Two phase AC) = (1 * 746)/(230 * 0.9 * 0.83 * 2)
I (Two phase) = 2.17 Amps
Three phase system
Example: A three phase, 1 HP, 230-volt motor having EF rating 85% operates at PF of 80%. Find the current drawn by the motor.
Solution: I (Three phase AC) = (1 * 746)/(230 * 0.85 * 0.8 * 1.73)
I (Three phase AC) = 2.75 Amps
So that was all about amps calculation from HP.
Let’s revise the formulas once: