Need A Variable Frequency Drive To Control The Speed / Soft Start Your AC Or DC Motor?
These Static Phase Converters Will Convert Single Phase 120 VAC, 240 VAC, 480 VAC or 600 VAC Input Power To Three Phase Output Power For Motor Applications
These Static Phase Converters Will Convert Single Phase 120 VAC, 240 VAC, 480 VAC or 600 VAC Input Power To Three Phase Output Power For Motor Applications
First off, if you need a variable frequency drive for your AC motor, make sure you check out our web store. Calculating RPM for a three phase induction motor is relatively simple… AC Three Phase Induction Motor RPM is determined by the formula:
Since the number of poles of a three phase induction motor is established when it is manufactured, the only way to change the speed of the motor is to change the Frequency.
For Example: A four pole three phase induction motor when operated at 60 Hz will be very close to 1800 RPM(synchronous speed). The rated full load speed will be less than synchronous speed by the value of “Slip”. A four pole three phase induction motor with a rated full load speed of 1750 has a slip rating of 2.7%. By formula:
When using this information and the above formulas the running speed of an AC three phase induction motor can be calculated at any input frequency. So how fast will a four pole three phase induction motor run when operated at 45 Hz? The three phase induction motor has a Full Load RPM rating on the nameplate of 1760 RPM.
Next, we calculate the Slip Rating:
Instead of using a percentage, we will convert the Slip Rating into how many RPMs actually slip using the following formula:
So full load RPM of this motor at 45 Hz will be calculated as such:
Note: If the load is less than the available torque output from the motor the RPM will be higher than full load RPM but will never be at synchronous speed for any given frequency. All of this information pertains to Squirrel Cage type AC three phase induction motors.
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