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Gibbons jargon buster #1: What is a squirrel cage rotor?

Here at Gibbons Group we understand that in our business there’s a lot of terminology used that may not mean much to those outside the industry. That’s why we’re going to explain some of the more confusing expressions you may come across when dealing with variable-speed drives, pumps, electric motors, control panels and more.

To get us started, we’re going to answer a common question in the electric motor world – what is a squirrel cage rotor? As we know, the rotor is the moving part of a motor (with the stator being the stationary part). The majority of AC induction motors have a squirrel cage rotor, or simply a cage rotor as it’s sometimes referred to. A squirrel cage rotor is so called because of its resemblance to a hamster wheel. This photograph shows a squirrel cage rotor:

If you’re struggling to see the similarity then imagine that the steel laminations are removed (see image below) and you’ll see that internally the rotor is made up of conducting bars, which is where the term ‘squirrel cage’ originates.

Here’s how a squirrel cage rotor works:

  • The rotating magnetic field from the stator penetrates the rotor bars and induces current in them.
  • The current flows through the bars to an end ring, transfers to the bar on the opposite side of the rotor then returns through the other end ring.
  • This creates a magnetic field in the rotor that follows the stator’s magnetic field and causes the rotor to turn.

So there you have it! If you have any technical questions for the friendly Gibbons team, don’t hesitate to call us on 01621 868138 or email

Electric Motors

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