Discuss three phase single phase in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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crissy_7

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Hi recently brought an old compressor is currently wired to three phase but can apparently be used on 230 single phase (it actually says this on the compressor) the wires coming from the motor are 2x black 2x red/orange 2x green, they are laid out as below there are three bars which are moveable joining the top three terminals my question is where do i join the live, neutral and earths? any help would be greatly appreciated alternatively you could reccomend an electrician in the Bristol area that would carry this out
regards
Chris

R B G

B G R
 
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M

montybaber

  • Thread Starter Thread Starter
  • #2
hi there

can you tell me what information is on the motor nameplate (exactly) it looks to me to be a three phase motor wired in star configuration.
 
C

crissy_7

  • Thread Starter Thread Starter
  • #3
HI the junction plate says:
mot type 80/4
Kw/hp 0,55/0,75
volts 240/415
R.p.m 1340
amps 2,7/1,56
here are pics of junction box innards
thanks
chris



 

ian.settle1

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Mentor
Arms
I think you will find it is talking about 240 v 3 phase and not 240v single phase.

The reason you have 2 of each colour is that they are they ends of each winding, and from photo it is wired in star so there is NO neutral required, the earth will connect to the stud in top right hand corner of terminal box.

do you have a photo that is more in focus?
 
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montybaber

  • Thread Starter Thread Starter
  • #5
im no expert so please anyone on here more intelligent than me (99% me thinks:)) please dont flame me lol

The motor shown is a three phase motor, what the nameplate is telling you that in star connection you effectively achieve 230v across each winding, connected in delta however you have 415v and that is why the nameplate shows 415/230v (delta/star) and then each piece of info is giving the motors rating with each method of connection.

I'm afraid to run this motor you require a three phase supply, to my knowledge the only other way is to run it using a 230v inverter (VVVF drive) connected in delta configuration, whether this is possible in this particular application is another story (cant see why not if the motor is small enough (up to 2.2kw on movitrac drives) and as long as the specified frequency/voltage runs the motor at the compressors req'd speed etc)

hope thats some help
Craig
 
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Incomp51

  • Thread Starter Thread Starter
  • #6
Have a look on EBay..... there's a 1.5HP Omron inverter for sale that may do the trick otherwise a new single phase motor is the way.
 

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