How real electric motors work
John Storey
Note: These pages are intended to be read in conjunction with Joe's "Electric motors and generators"
pages (http://www.animations.physics.unsw.edu.au/jw/electricmotors.html). Read those pages first. Once you've
got the basic idea and understand the physical principles and the maths, you're ready to explore how
real-life engineers have put physics into action to make our lives easier.
When it comes down to it, all these motor are using the same basic principle. In some cases, it’s
easiest to think in terms of the force on a current-carrying wire in a static magnetic field. In other
cases it’s easiest to think about two magnets (at least one of which is an electromagnet) attempting to
align their poles north-to-south and south-to-north. However, both these explanations amount to the
same thing, as James Clerk Maxwell so elegantly described with his four equations that form the basis
of electromagnetism. http://www.phys.unsw.edu.au/einsteinlight/jw/module3_Maxwell.htm
If you're tempted to pull a motor apart yourself, please think carefully about the risks involved before
reaching for the tool kit. Some of the more important risks are listed at the end of this article.
Click on any picture for a high-resolution image. All pictures may be freely reproduced for
educational purposes provided they are appropriately acknowledged.
1. Induction motors
2. “Universal” motors
3. Advanced AC motors
4. “Conventional” DC motors
5. Printed circuit motors
6. Brushless DC motors
7. Stepper motors
8. The infamous “ball-bearing” motor
9. Taking motors apart.
UNIVERSITY OF NEW SOUTH WALES - SYDNEY - AUSTRALIA
1. Induction motors
No modern home should be without one – or maybe a dozen. You'll find an induction motor in the
fan, fridge, vacuum cleaner, washing machine, dishwasher, clothes drier, and the little pump that
circulates water in the fish tank to stop the water turning green and the fish going belly-up.