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Simple but clever motor wiring

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Pete.:

--- Quote from: Will_D on October 15, 2015, 06:26:16 AM ---So just to be totally clear:

Am I correct: Grey is the Neutral and either Brown or Black is the live (depending on direction you want)?

--- End quote ---

Hi Will,

Yes, that would be right.

Pete.:

--- Quote from: DavidA on October 15, 2015, 12:02:12 PM ---Arbalist,

The only real problem with that approach is that the efficiency depends upon the capacitor being reasonably close to the ideal for the load.

Running a three phase motor on a single phase supply with a badly matched capacitor will result in the motor overheating.

It's quite easy to work out the correct value; as long as you know the load.

Dave.

--- End quote ---

David,

I'd like to know how because my tool & cutter grinder has a capacitor and it struggles to come up to speed when it's cold. The motor also runs quite warm.

DavidA:
Pete,


Capacitance = Amps/(2*Pi* Frequency*Volts)

I'm assuming that you  have a three phase motor running off a single phase supply.

If you measure the voltage of each phase when your motor is running, and the current, then you should get an indication of which way to adjust your capacitor.  In the ideal world the voltages will be the same.
Maybe you need an extra starting capacitor.

Dave.

Pete.:
Easy as that eh? Thanks David I'll get my multimeter out.

BillTodd:
That's not an unusual configuration for a  capacitor start/ motmotor. If the start and run windings are the same then a simple change over switch is all that's needed to reverse it.

(just so happens that my dad made me a toy with one in and showed me how it worked while i was at primary school! :-)  )

The diagram below shows a typical configuration and how the third phase of a 3ph motor would be in parallel with the start/run cap.

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