3 hp Single phase Motor?

Question

How to calculate the Starting AMP of this 3 horsepower single phase motor whereby if i use D.O.L starter and Soft Starter?

Answer 1

well first you have to multiply 3hp by 746.Then you obtain 2,238 watts.Then you apply the watt's law that is W=VOLT X AMPS,AMPS=WATTS/VOLTS,
VOLS=W/AMPS

if the motor 120 or 240 volts????

if it is 120 volts the amps will be 18.65

if it is 240 volts the amps will be 9.32

HOPE THIS HELP!!!!!

746 IS THE NUMBER TO CONVERT HP IN WATTS(watts is the same that volts-amps)

Answer 2

Typically the starting current for a squirrel cage motor (single or 3PH) is 6 time the full load current.
Look at the motor amps and multiply by 6 and you will have the appoximate starting current for DOL.
As I stated X6 is nominal, however some motor designs have higher starting current values - up to around 9 and some deep bar rotor designs have lower starting values. down to around 4 times.
With a soft starter the starting current is limited by the voltage rise of the soft starter. The voltage at start is very low and rises over a time period to full voltage. The motor at some stage during the voltage rise will reach "Break Away Torgue" and slowly accelerate to full speed. As the voltage is low at BAT the current will build up gradually from zero to full load current. Therefore at start the current is 0 to slowly rise to FL current.

Souce: Electrical Engineer with 40+ years experience

Answer 3

The starting current of a motor is usually double the maximum run current. Figure the maximum running current as stated above using 2237 volt-amps divided by the operating voltage then just double the number.

Answer 4

Bazza66 is right on...