Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Electrical Induction Motors - Synchronous Speed

Operating speed of an induction motor depends on the input power frequency and the number of magnetic poles in the motor.

The synchronous speed for an electric induction motor is determined by

  • the power supply frequency, and
  • the number of poles in the motor winding. 

The synchronous speed can be calculated as:

n = f (2 / p) 60                      (1)

where

n = shaft rotation speed (rev/min, rpm)

f = frequency of electrical power supply (Hz, cycles/sec, 1/s)

p = number of poles

Electric motors - Synchronous speed vs. frequency and no. poles

Note - an induction motor will never reach its synchronous speed. If it did - the rotor would appear to be stationary to the rotating stator field since it would rotate with the same speed. With no relative motion between stator and rotor field no voltage will be induced in the motor. The speed of an induction motor is therefore limited to a speed below synchronous speed and the difference between synchronous speed and actual speed is called slip.

Example - Synchronous Speed of Electric Motor with Two Poles

A motor with two poles is supplied with power with frequency 50 Hz (1/s). The rotation speed can be calculated as

n =  (50 1/s) (2 / 2) (60 s/min) 

   = 3000 rpm (1/min)

Synchronous rotation speed at different frequencies and number of poles

Electrical Induction Motors - Synchronous Speed
Shaft rotation - n - (rev/min, rpm)
Frequency
- f -
(Hz)		Number of poles - p -
24681012
10 600 300 200 150 120 100
20 1200 600 400 300 240 200
30 1800 900 600 450 360 300
40 2400 1200 800 600 480 400
501) 3000 1500 1000 750 600 500
602) 3600 1800 1200 900 720 600
70 4200 2100 1400 1050 840 700
80 4800 2400 1600 1200 960 800
90 5400 2700 1800 1350 1080 900
100 6000 3000 2000 1500 1200 1000
  1. Motors designed for 50 Hz are most common outside U.S
  2. Motors designed for 60 Hz are most common in U.S

Electric motors - frequency, no. of poles and synchronous speed

Variable Frequency Drive

A variable frequency drive modulates the speed of an electrical motor by changing the frequency of the power supply.

Related Topics

  • Electrical

    Electrical engineering with units, amps and electrical wiring. Wire gauges, electrical formulas, motors and more.

Related Documents

Search

Search is the most efficient way to navigate the Engineering ToolBox.

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

Citation

This page can be cited as

  • The Engineering ToolBox (2004). Electrical Induction Motors - Synchronous Speed . [online] Available at: https://www.engineeringtoolbox.com/synchronous-motor-frequency-speed-d_649.html [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter

















































4.26.8

.