Electric Motor Rpm Formula

50hz is the most common frequency outside the us.

Electric motor rpm formula.

At 1800 rpm a motor develops a 3 lb ft. I input dc current. Per hp at 1200 rpm a motor develops a 4 5 lb ft. Hz frequency or cycles sec.

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. 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. T inlb torque in lb f. 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.

Calculating the rpm resulting from a motor and speed reducer assembly requires only basic mathematical knowledge. Check the circle next to the item you are solving for and enter the remain three items in the spaces provided. So for example if you have a 4 pole motor on 60 hz then rpm 60 2 4 60 1800 rpm. T v x i 2 x pi x n rpm 60 n rpm is the speed of the motor.

T ftlb torque lb f ft. Note that when an ac motor is loaded the spinning magnetic field in the stator does not change speed. Here omega ω is equal to 2 x pi x n rpm 60. Rpm 120 frequency of poles in the motor.

For a 50 hz system the formula would be. V input dc voltage. At no load you have maximum speed and zero torque. T inlb p hp 63025 n 1.

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. Electrical motor power velocity and torque equations. Hence motor torque t p ω. 50 x 60 x 2 6 000 no load rpm ã number of poles.

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. Rpm shaft rotation speed or revolutions per minute. 1750 rpm 1000 rpm 3 5 inches d 2 d 2 6 125 inches.

60hz is the most common frequency in the us. N revolution per minute rpm alternatively. For calculating torque for dc motor. For dc motor torque formula.

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. Motor torque changes with the speed. Pulley and speed calculator. T ftlb p hp 5252 n 1b.

Acthree phase induction motorrpmis determined by the formula. 1 ft lb f 1 356 nm. P hp horsepower delivered by the electric motor hp. Torque in imperial units can be calculated as.