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Topic Title: Connecting a single phase motor
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Created On: 30 June 2013 03:57 PM
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 30 June 2013 03:57 PM
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Helping a friend reuse a single phase motor. It has I think 4 wires going into it. They are connected (I think) to P, U and K on the attached photograph.

Clearly 240V across U & K - but I suspect there was a switch in the wires P-U.

But what do I know...

Any body here help me understand this please? Motor is rated 900W.



 15 July 2013 07:59 AM
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Why do believe it is 4 wire when the diagram shows 2 + earth ?
Do you know what the motor is intended to drive ?
Do you know what the switch Z1 is for - is it internal ?

Have you connected as shown ?
There could well be a switch between P and U connectors, to open once the motor had started.
 18 July 2013 08:45 PM
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I suspect the switch is internal overload / thermal protection
 03 October 2013 02:38 AM
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hi oneye,

This looks to me like a more fanciful version of the several capacitor Start/Run single phase motors which drive my several pumps. Basically these are a 2-phase motor in which the secondary winding is fed via a capacitor to produce the phase shift required to produce a spinning magnetic field. Monkey about with the connections and you can make such a motor run the "wrong" way.

A built-in thermally-operated switch is not uncommon; e.g. in my borehole pumps thermal protection is necessary in case the pump is powered when the borehole lacks water - in general water pumps are cooled by their own product.

Ken Green
 09 January 2014 05:15 PM
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Remove the space after www. and the above link shows various wiring configurations of this type of motor.
 20 March 2014 07:35 PM
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I fully agree with reply made by kengreen.
I will add only one point that in addition to connecting single phase supply to terminals K and U, make sure that there is jumper between terminal P and U.

Electrical engineer with more than 20 years of experience in petrochemical plant project management, commissioning, maintenance and technical support.

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