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About Motors

Modern electrical motors are available in many different forms, such as single phase motors, three-phase motors, brake motors, synchronous motors, asynchronous motors, special customized motors, two speed motors, three speed motors, and so on, all with their own performance and characteristics.

Softstarter Handbook - ABB
Softstarter Handbook – ABB

For each type of motor there are many different mounting arrangements, for example: foot mounting, flange mounting or combined foot and flange mounting.

The cooling method can also differ very much, from the simplest motor with free self-circulation of air to a more complex motor with totally enclosed air-water cooling with an interchangeable cassette type of cooler.

To ensure a long lifetime for the motor it is important to keep it with the correct degree of protection when under heavy-duty conditions in a servere environment.

The two letters IP (International Protection) state the degree of protection followed by two digits, the first of which indicates the degree of protection against contact and penetration of solid objects, whereas the second states the motor’s degree of protection against water.

The end of the motor definition
The end of the motor definition

The end of the motor is defined in the IEC-standard as follows:

  • The D-end is normally the drive end of the motor.
  • The N-end is normally the non-drive end of the motor.
Note that in this handbook we will focus on asynchronous motors only.

Squirrel cage motors

In this book the focus has been placed on the squirrel cage motor, the most common type of motor on the market. It is relatively cheap and the maintenance cost is normally low.

There are many different manufacturers represented on the market, selling at various prices.

Not all motors have the same performance and quality as for example motors from ABB. High efficiency enables significant savings in energy costs during the motor’s normal endurance. The low level of noise is something else that is of interest today, as is the ability to withstand severe environments

Title:Softstarter Handbook – ABB Automation Technology Products AB, Control
Size:7.6 MB
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Softstarter handbook - ABB Automation Technology Products AB, Control
Softstarter handbook – ABB Automation Technology Products AB, Control

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More Information


  1. Suriyavarman Naidu
    Dec 18, 2019

    Very good information

  2. Atahar Ayyub
    Jan 24, 2019

    IP means Ingress Protection, Not International Protection (Refer IEC 60529).

    • Rob Eagle
      Sep 05, 2019

      It is International Protection, see BS EN 60529 Section 4 “Designations” and 4.1 “Arrangement of the IP code”.

  3. Oluwaji Oluwatosin
    May 29, 2018

    Very good and useful! thanks!

  4. El jaafari mohammed
    Mar 08, 2016

    dear sir,
    i’m a beginner in electrical enginnering and i want to know how to calculate the limit of current when i have a blocked rotor(jam protection) in a pump application.


  5. sinnadurai sripadmanabn
    Sep 07, 2015

    Please give load characteristics of various types of pumps,conveyors,crushers,compressors etc and torque produced by each type of motors to select suitable starter.

  6. Vicente Martinez
    Aug 12, 2015

    Very good information, thank you

  7. Deo Ybarrita
    Jul 19, 2015

    Dear sir,

    Please provide the correct size of circuit breaker for a variable speed drive motor with a name plate full load current of 138A.

  8. Ali
    Apr 19, 2015

    Dear Sir,

    I need the circuit diagram of the Siemens soft starters RW40 56



  9. Bhabendra Muktan
    Feb 19, 2014

    Good article but is IP not suppose to be Ingress Protection rather than International Protection?

    • sagar gawali
      Jul 30, 2015

      ingress protection is correct word.

  10. morteza
    Feb 09, 2014

    Thanks for the useful information and documents.
    as always

  11. youssef
    Jan 26, 2014

    I am looking for a sponsor to certify innovative features of three-phase induction motor has to participate in the exhibition

  12. wc_foronda
    Oct 17, 2013

    Problem opening file format after succesful download,..

  13. José Santana
    Jun 22, 2013

    Very good material.

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