Menu
Search
Motor action
Figure 1 - A motor action

The basic working of a motor is based on the fact that when ‘a current carrying conductor is placed in a magnetic field, it experiences a force’.

If you take a simple DC motor, it has a current-carrying coil supported in between two permanent magnets (opposite pole facing) so that the coil can rotate freely inside. When the coil ends are connected to a DC source then the current will flow through it and it behaves like a bar magnet, as shown in Figure 1.

As the current starts flowing, the magnetic flux lines of the coil will interact with the flux lines of the permanent magnet.

This will cause a movement of the coil (Figures 1a, 1b, 1c, 1d) due to the force of attraction and repulsion between two fields. The coil will rotate until it achieves the 180° position, because now the opposite poles will be in front of each other (Figure 1e) and the force of attraction or repulsion will not exist.

The role of the commutator: The commutator brushes just reverse the polarity of DC supply connected to the coil. This will cause a change in the direction of the current of the magnetic field and start rotating the coil by another 180° (Figure 1f).

The brushes will move on like this to achieve continuous coil rotation of the motor.

Similarly, the AC motor also functions on the above principle; except here, the commutator contacts remain stationary, because AC current direction continually changes during each half-cycle (every 180°).

Resource: Practical Troubleshooting of Electrical Equipment and Control Circuits – M. Brown
(Get it from Amazon)

About Author //

author-pic

Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on

9 Comments


  1. Wayne A. Francis
    Dec 28, 2014

    Very simple and effective disposition of technical information. Keep up this good work.


  2. suhasini
    May 18, 2014

    Awesome effort by the contributors of EEP. Have I had a source like this during my graduation, I would have been in a super cool hard core engineering job!!! Anyways better late than never..so I still try to learn whenever possible


  3. Joshua
    May 18, 2014

    How can I determine the power factor in a three phase motor?


  4. joshua
    May 18, 2014

    I love this site ,it helps me develop my engineering skills

  5. […] keep this torque angle constant as the rotor spins on its shaft, a mechanical switch, called a commutator, is configured so the current distribution in the rotor winding remains constant, and therefore the […]


  6. Mani Manz
    Aug 21, 2013

    clearly said . . . the non alignment of two magnetic fields makes the motor to rotate continously. . .


  7. sasi kumar
    May 29, 2013

    very nice, Thank you


  8. Md Ebrahim Shah
    Feb 24, 2013

    motor is just a device which convert electrical energy to rotation energy.


  9. chavan2294
    Feb 08, 2013

    wonder full, with simple language, thank you sir for your great contribution in electrical field

Leave a Comment

Tell us what you're thinking... we care about your opinion!

Time limit is exhausted. Please reload CAPTCHA.

Get PDF