Welcome to our electric motor RPM calculator! This page will allow you to calculate the motor speed of an AC induction motor using the supply frequency and the number of pole pairs within the motor.
Motor speed is an essential parameter in electric motor design. As such, it should be considered carefully.
Calculation
Inputs
Frequency
:60Hz
P (Pole Pairs)
:4
Output
Nm
:1800
Nm, Rad/s
:188.495559
Explanation
AC induction motor speed depends on the supply frequency and the number of pole pairs. To regulate the speed of an AC induction motor, one must vary these two variables to achieve the desired speed. There are also other methods of speed regulation:
🏎 Methods of Speed Control
Voltage Control Method
As per the name, this method of speed control is associated with varying the supply voltage to achieve the desired speed. This method is cheap and easy, however, is uncommon due to the fact that a large change in supply voltage is required to produce a small change in speed.
Frequency Control
As the calculation template demonstrates, increasing or decreasing the frequency will result in a changing motor speed. A combined frequency and voltage speed control method known as V/F control is utilised in most induction motor applications.
Pole Changing
As per the calculation template, increasing or decreasing the number of pole pairs in an induction motor will vary its motor speed.
🏍 Types of Motors and their uses
There are two main types of motors: AC and DC. Each type has subtypes that are utilised for different applications.
DC Motors
AC Motors
Induction Motor
An induction motor is a type of motor that utilises an AC supply voltage to produce mechanical work.
Induction motors consist of a rotor and a stator. The stator consists of a ring of tightly wound electromagnets and the rotor is either a squirrel cage (two metal rings attached via skewed rotor bars) or a slip ring construction (cylindrical laminated core with parallel slots).
As 3-phase AC power is applied to the stator, it begins to produce a rotating magnetic field. Current is then induced in the rotor producing its own magnetic field. The interaction of these two magnetic fields enables the rotor to spin at a rate that is always lagging the stator field. This is known as slip.
Induction motors are widely used in many different industries, from transportation to HVAC systems to oil extractions. They are used in pumps, fans, toys, vacuums, electric vehicles and many other applications.
Synchronous Motor
A synchronous motor is another type of AC motor that is frequently used in many industries.
Synchronous motors have a stator consisting of a series of electromagnets. The rotor is comprised of a cylindrical bar of either a salient or non-salient type construction (meaning projected out or not projected out). An external dc voltage supply is also attached to the rotor.
As 3-Phase AC voltage is supplied to the stator, it begins to produce a rotating magnetic field. The induced voltage is then produced in the rotor. An external DC source is then supplied to the rotor and enables the rotor's magnetic field to link with the stator's magnetic field thus producing a final speed.
Synchronous motors are used in applications that require precise positionings such as actuators, watches and record players.