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'[EE]: Induction motor connections ?'
2002\01\28@003131 by arpit

Hi, I have a large induction motor used to spin the drum of a photocopier. I scavenged it when I was about 10, and now 5 years later, I don't remember what the connections were. I has three wires. I remember hooking one to earth a couple of years ago and getting a very severe electric shick from it. Since then I have learnt that it probably needs a starting capacitor, for when I hook any 2 of the leads to the mains, it just sits there and hums, until I start it off on either direction. I have no idea about the connections to the starting capacitor though.

The resistances are as follows:

white-black  56ohms
white-grey   155ohms
Grey-black  100ohms.

On the package it has the following technical information:

Induction Motor
uF -3

I have located a 480 volt 3 uf capacitor which probably came from the same photocopier.  Could someone please enlighten me as to how to connect it?
Thanks, Arpit.
Photos of the motor are on my website at

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2002\01\28@055936 by Mike Blakey

From your post, you could try this....

When playing around with this sort if equipment, it is a good idea to put a 60W
lamp in series with the LIVE.
That way, if you short-circuit or connect the motor incorrectly, you wont blow the
motor or the supply fuse.

                                    | |
                                    | |
                       +------------| |-------------------Grey  +
                       |            | |                         )
                       |            | |                         )
                       |                                        )
                       |            3uf                         ) 100 Ohm
                       |                                        )
                       |                                        )
                       |                                        )
live 240vac ------------+----------------------------------White +
                                                                ) 55 Ohm
Neutral ---------------------------------------------------Black +

Earth -----------------------------------------------------Case

Dont forget to EARTH the Motor CASE, AND the capacitor IF it has an EARTH tag.

Take Care switching these things, they are inductive and can bite!

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2002\01\28@061956 by arpit

Thankyou very much for your tim and trouble to put together the diagram. I will try it tomorrow.

*********** REPLY SEPARATOR  ***********

On 1/28/2002 at 10:07 AM Mike Blakey wrote:

{Quote hidden}

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2002\01\29@145955 by Peter L. Peres

picon face
> white-black  56ohms
> white-grey   155ohms
> Grey-black  100ohms.

White is common, black is phase and the cap goes between black and grey.

I may be wrong however, the connections could be the other way around. You
use this at your own risk.


PS: The rationale is, that the larger resistance winding uses less current
and/or has thinner wire and should be connected to the cap. The lower R
one will have lower I^2R losses so it is most likely to go directly to the
mains phase.

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