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Discuss Wiring diagram for a 3 phase motor on single phase supply in the Electrical Forum area at ElectriciansForums.net

M

Micklane

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A customer has an existing application using 2 off, 4 pole contactor/relays of Brook Crompton make, model HR1310 and 3 capacitors of 200, 60 and 20 microfarads. The 3 phase motor is an English Electric, 4 pole with nameplate details - 2 HP, 400/440, star connected, (but the motor may be delta connected for 240 volts). This motor is on a lathe and the controls are inside a metalclad box with a start and a stop pushbutton. The supply is at 240V single phase from a 13A plug.

The fact that the relays are of Brook Crompton make, suggests that this was a proprietary method of this application.

I realise that this setup using discrete relays for the control is out of date, but has anyone got a wiring diagram for this unit? One of the relays is immediately energised when power is switched on, and I think the other relay should briefly switch on the start capacitor (the 200 microfard, I think), to start the motor from the start pushbutton, i.e. this relay is not retained.

The owner has replaced the relay for running, since it "was always energised" and the motor could only be stopped by switching off at the 13A plug. It appears that he has miswired the relay, since that relay energises but nothing else works!.

An inverter is an option, I haven't pursued this route but they are expensive, as is a single phase motor.

Regard
 
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O

oldtimer

  • Thread Starter Thread Starter
  • #2
Emm you will not get a 3 phase motor to work on a single phase supply Do you mean how do you wire a single phase motor on to a 3 phase contactor overload setup
 
K

Knobhead

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  • #4
There is a way of running it without an inverter, it’s expensive and inefficient. Go for the inverter.
 
B

Bobster

  • Thread Starter Thread Starter
  • #5
This probably isn't the same set up you have, it may help. It's the only way I've seen in person a 3ph motor running on a single phase supply.


 
M

Micklane

  • Thread Starter Thread Starter
  • #6
Emm you will not get a 3 phase motor to work on a single phase supply Do you mean how do you wire a single phase motor on to a 3 phase contactor overload setup
Not true, this existing application for a hobbyist in this case, is an older method of conversion using 3 capacitors and a start/stop pushbutton; and originally supplied by Brook Motors as I understand. Inefficient but practical at the time before inverters.

Regards
 
O

oldtimer

  • Thread Starter Thread Starter
  • #7
Not true, this existing application for a hobbyist in this case, is an older method of conversion using 3 capacitors and a start/stop pushbutton; and originally supplied by Brook Motors as I understand. Inefficient but practical at the time before inverters.

Regards
OK but never seen this elsewhere
 
B

Bobster

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  • #8
Try looking up a "steinmetz connection"

 
K

Knobhead

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  • #9
Not seen that one before. Every day, something new :hurray:
 

darkwood

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get it pasted in the motor 'sticky' thread, new on me too, damn i didnt know everything ;)
 
B

Bobster

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  • #11
No worries fellas :)

Just remembered some of the theory one of my lecturers told us about after we got him off curriculum.
 

PEG

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This thread is a lovely reminder of work in old joinery shops where the old dodgers called it a "slave" or "sacrificial" geny set-up.I remember the capacitors were old then and had to be matched carefully or replaced in branded groups.They sometimes "up-dated" using big whiny single phase close coupled 3 phase converters that sat in the corner covered in sawdust! Whats CE rating again?.......
 

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