I scavenged a 220 volts DC motor from a large photocopy machine.

How can I best get a suitable 220 volts DC supply when our local main supply is 240 volts AC? Since the voltages are so close is there a cheap way to convert type of current on a one-to-one basis like this?


How was it powered in the original copier?

Is it a permanent magnet motor, or does it have a field winding?

EDIT : the linked picture strongly suggests a PM DC motor NOT a Universal motor so the main part of this answer is wrong. Left for the moment but it should probably be deleted.

If the latter (most likely for an older large DC motor) it's actually a "Universal" motor and will work equally well off AC or DC. And a close inspection of the copier will probably reveal a connection directly to the AC supply.

Universal motors work on AC because, when the voltage to the rotor reverses polarity, so does the voltage supplied to the field coil, so the resulting "push" remains in the same direction.

Then a straight connection to 230V AC would be better (the right voltage!) than converting the incoming AC to DC, which, if you smoothed it with a reservoir capacitor, would give you somewhere over 320V DC.

On the other hand if it is a permanent magnet rotor, a bridge rectifier and no smoothing capacitor will generate "dirty DC" of the right RMS voltage. But be aware that the peak voltage is still too high, which could stress the insulation.

  • \$\begingroup\$ I have tried hard to find a data sheet and have just written to the manufacturers maybe they will come through for me. All I know so far is its a motor also used within a Duplo copier. I found it listed as a "Single-phase asynchronous motor", "2 poles", "60/80 Watts","3500 rpm". Its made by Matoba Electrical and has the code type F7-81460. I will post again if I get a reply and hopefully a datasheet. \$\endgroup\$ – Galahad II Oct 15 '14 at 21:13
  • \$\begingroup\$ If this is correct, your original question is wrong and so is my answer. If it's a single phase motor it's not a DC motor! 3500rpm is about the right speed for an AC induction motor (asynchronous) running off 60Hz AC. But 60Hz AC would suggest 110V not 230V... Look at the motor ... does it have brushes and a commutator? If so, it's not an induction motor! \$\endgroup\$ – user_1818839 Oct 15 '14 at 21:24
  • \$\begingroup\$ Pic of universal motor... electronics.stackexchange.com/questions/65330/… \$\endgroup\$ – user_1818839 Oct 15 '14 at 21:33
  • \$\begingroup\$ I don't know how to attach a picture here. However I did find an image of the motor at: 2ememain.be/electrom%C3%A9nager/electrom%C3%A9nager-divers/… \$\endgroup\$ – Galahad II Oct 15 '14 at 21:37
  • \$\begingroup\$ By the way, why are you replying with a comment rather than an answer? I am new to this and don't really understand the way it works. but I would have thought you get more points for an answer? \$\endgroup\$ – Galahad II Oct 15 '14 at 21:41

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