Brushed DC Electric Motor Used as a Generator

  1. I was wondering whether there was any literature on brushed DC motors used as a generator or whether you know anything of the sort? I know that DC motors behave differently when used as a generator instead of a motor. However I have not been able to find anything about it so I was wondering whether there is any information about it? Thanks for the help.
  2. jcsd
  3. yes you could if you can spin it fast enough. But you notice how hard it is to spin the big ol thing? wouldnt produce to much power. you can make it power your workstation LED lights
  4. jim hardy

    jim hardy 5,460
    Science Advisor
    Gold Member
    2014 Award

    look up "dynamo"

    in general there is no difference between a DC generator and DC motor

    a small permanent magnet motor will make near its nameplate volts and amps if you turn it in its operating range

    if it's a wound field motor it needs to be provided with field current

    there's plenty of tutorials about at many levels of sophistication, let a search engine be your friend.
  6. I used my dremel to test my brushed motor. 8000rpm it makes about 4volts. @35000 rpm it made 11 volts
  7. jim hardy

    jim hardy 5,460
    Science Advisor
    Gold Member
    2014 Award

    how much field was on it?
  8. not sure how to test for the field
  9. jim hardy

    jim hardy 5,460
    Science Advisor
    Gold Member
    2014 Award

    how many terminals does it have?
    what does it do if you apply 11 volts (12 probably close enough)?

    There's two basic formulas for DC machines

    Volts = k X flux X rpm
    where k is a constant for the motor's physical design
    flux is magnetic field inside, either from a permanent magnet or the combination of all its field windings
    rpm is of course rpm

    Torque = 7.04 X k X flux X Iarm
    k same as determined from open circuit speed test (which you did with Dremel)
    flux same as above
    Iarm is current through armature

    If it has only one terminal, try connecting a lamp to it while spinning with dremel. If voltage goes up, lamp lights and dremel slows down, it's a series field
    if voltage collapses it may have a defective field.
  10. its a vintage titan motor. has 2 terminals pos & neg. Cant read the lable any more on it.
Know someone interested in this topic? Share this thead via email, Google+, Twitter, or Facebook

Have something to add?