Note that when an ac motor is loaded the spinning magnetic field in the stator does not change speed.
Electric motor rpm formula.
The speed of the motor can be found by using speed measurement devices.
50hz is the most common frequency outside the us.
I input dc current.
Motor torque changes with the speed.
60hz is the most common frequency in the us.
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.
N revolution per minute rpm alternatively.
So for example if you have a 4 pole motor on 60 hz then rpm 60 2 4 60 1800 rpm.
T inlb torque in lb f.
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.
Rpm 120 frequency of poles in the motor.
Here omega ω is equal to 2 x pi x n rpm 60.
P hp horsepower delivered by the electric motor hp.
T inlb p hp 63025 n 1.
Below is a small calculator that will solve the ratio for you.
Torque in imperial units can be calculated as.
For calculating torque for dc motor.
Check the circle next to the item you are solving for and enter the remain three items in the spaces provided.
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.
At 1800 rpm a motor develops a 3 lb ft.
Hence motor torque t p ω.
1750 rpm 1000 rpm 3 5 inches d 2 d 2 6 125 inches.
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.
T ftlb torque lb f ft.
1 ft lb f 1 356 nm.
Per hp at 1200 rpm a motor develops a 4 5 lb ft.
Rpm shaft rotation speed or revolutions per minute.
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.
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.
For a 50 hz system the formula would be.
Poles number of poles of your motor.
Acthree phase induction motorrpmis determined by the formula.
Hz frequency or cycles sec.
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.
T v x i 2 x pi x n rpm 60 n rpm is the speed of the motor.
50 x 60 x 2 6 000 no load rpm ã number of poles.
Pulley and speed calculator.
T ftlb p hp 5252 n 1b.
Electrical motor power velocity and torque equations.
For dc motor torque formula.
