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How are electric motor frame sizes calculated?

When you order an electric motor from Gibbons, one of the first pieces of information we’ll need is the frame size required. As a general rule, the larger the frame size, the greater the motor’s output. But how exactly are electric motor frame sizes calculated?

To explain frame sizes, it’s necessary to understand a motor’s full model code. For this we’ll use a Gibbons M Series electric motor with model number MY712-2 as an example. This motor has the following characteristics:

  • MY - The initial letter(s) are manufacturer specific.
  • 71 - The first numbers denote the motor’s frame size (the distance, in millimetres, from the underside of the feet to the centre of the shaft). This generally begins at 56 and can be anything up to 450.
  • 2 - The next digit refers to lamination pack length, with 1 being the shortest. Pack length is normally 1, 2 or 3 but can be even greater. Some manufacturers use a numbered system while others prefer letters.
  • 2 - The final digit refers to pole speed, which will usually be two, four, six or eight.

If you’re unsure about any aspect of electric motor designation, contact us on 01621 868138 or email and one of our friendly team will be on hand to help. You can also browse our range of ABB electric motors, along with our own high-performance selection. 

Electric Motors


  • Date: 21 November 2016 vinayagamj
    i want to know how motor frame size,base holes,shaft height calculate if mthere is any formula please help me
  • Date: 22 November 2016 Arun Kumar
    Mechanical Dimensional detail of BHEL Make HT 6.6 kV, 745 RPM, 560 kW, Foot Mounted, Frame Size HDS560, Ins. Class: F Motor detail required.
  • Date: 22 November 2016 Gibbons Engineering Group
    Thanks for your enquiries. Please email us at for assistance.

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