Electric Motor Rpm Formula

T ftlb p hp 5252 n 1b.

Electric motor rpm formula.

Rpm 120 frequency of poles in the motor. Check the circle next to the item you are solving for and enter the remain three items in the spaces provided. Note that when an ac motor is loaded the spinning magnetic field in the stator does not change speed. Motors run at a specific revolutions per minute rpm and a speed reducer is needed if you want to keep that motor but have a lower rpm.

The speed of the motor can be found by using speed measurement devices. N revolution per minute rpm alternatively. Acthree phase induction motorrpmis determined by the formula. 50hz is the most common frequency outside the us.

T inlb torque in lb f. Motor torque changes with the speed. Typical no load or synchronous speeds for an ac fractional horsepower motor are 1800 or 3600 rpm and 1000 5000 rpm for dc fractional hp motors. At 1800 rpm a motor develops a 3 lb ft.

Hence motor torque t p ω. Dc controls adjust speed by varying the voltage sent to the motor this differs from ac motor controls which adjust the line frequency to the motor. Below is a small calculator that will solve the ratio for you. Per hp at 575 volts a 3 phase motor draws 1 amp per hp at 460 volts a 3 phase motor draws 1 25 amp per hp at 230 volts a 3 phase motor draws 2 5 amp per hp at 230 volts a single phase motor draws 5 amp per hp.

T inlb p hp 63025 n 1. P hp horsepower delivered by the electric motor hp. Hz frequency or cycles sec. 50 x 60 x 2 6 000 no load rpm ã number of poles.

Per hp at 1200 rpm a motor develops a 4 5 lb ft. Torque in imperial units can be calculated as. T ftlb torque lb f ft. So for example if you have a 4 pole motor on 60 hz then rpm 60 2 4 60 1800 rpm.

1750 rpm 1000 rpm 3 5 inches d 2 d 2 6 125 inches. Calculating the rpm resulting from a motor and speed reducer assembly requires only basic mathematical knowledge. In our example input electrical power of the motor is 0 22 a x 6 v 1 32 w output mechanical power is 1000 rpm x 2 x 3 14 x 0 00126 n m 60 0 132 w. At no load you have maximum speed and zero torque.

For calculating torque for dc motor. V input dc voltage. For dc motor torque formula. T v x i 2 x pi x n rpm 60 n rpm is the speed of the motor.

Here omega ω is equal to 2 x pi x n rpm 60. Since the number of poles of athree phaseinduction motoris established when it is manufactured the only way to change the speed of the motor is to change thefrequency. Using this formula you can see that a four pole motor operating on the bench under no load conditions runs at 1 800 rpm 7 200 ã 4 poles. 60hz is the most common frequency in the us.

Poles number of poles of your motor. For a 50 hz system the formula would be. I input dc current. 1 ft lb f 1 356 nm.