5K40.40 Motor/Generator

Concepts

Electromagnetic induction, motors and generators, DC and AC signal generation

Overview

A loop of wire rotating between two permanent magnets generates DC and AC signals. This device can be connected to a DC power supply to run as a motor.

Details

Equipment

  • [1] CENCO motor/generator
  • [4] Metal brush
  • [1] Galvanometer
  • [2] Banana cable
  • [1] DC power supply (large current)

Classroom Assembly

Generator mode:

  1. Disconnect the DC power supply, if applicable.
  2. Connect the motor/generator to the galvanometer using banana cables.
  3. Place the meter under the document camera.

Motor mode:

  1. Disconnect the galvanometer, if applicable.
  2. Connect the motor/generator to the DC power supply using banana cables.

Important Notes

  • Do not run the motor/generator as a motor for extended periods of time.
  • If the motor does not turn when a large current is going through, turn off the current.

Script

Generator mode:

  1. Make DC connections by placing two metal brushes on opposite sides of the split-ring commutator.
  2. Rotate the handle and observe the galvanometer.
  3. Change the metal brushes to AC configuration, contacting to the continuous rings as shown in the picture.
  4. Rotate the handle and observe the galvanometer.
  5. Wiggle the coil back and forth at the positions of maximum flux through the coil (smallest generated voltage) and minimum flux (largest generated voltage).

Motor mode:

  1. Make DC connections by placing two metal brushes on opposite sides of the split-ring commutator.
  2. Turn up the current and get the motor started with a light spin. At maximum current and ~ 5 V, it should turn quite quickly.
  3. Turn off the DC power supply.

 

Additional Resources

References

  • PIRA 5K40.40

Disclaimer

  • Don't attempt this at home!

Last revised

  • 2020

Technicals

  • This thing originally came with some kind of electromagnet which disappeared years ago. Jeff Rudd stuck a couple of permanent magnets on it.
  • The motor/generator needs occasional maintenance to work in motor mode. The bearings need wiping and oiling; 3-in-1 oil works well. The brushes and contact rings need to have oxides stripped off; Scotch-Brite works well. The brushes should lightly touch the contact ring(s) without producing so much friction that the motor stalls.

Related AV

Related demos

If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.