3 Phase to Single Phase

[bcm_spark]

Evening all,

Got a 3 phase motor that needs to run on a single phase supply. I am probably talking (NO SWEARING) but I vaguely remember a few years ago a guy shorting out two of the phases on a motor and it worked on a single phase supply.

If the above is bollox, has anybody got a 230v 3KW motor they don't want?

Ben

 

[Darkwood]

Talking bol......., is the only thing that comes to my mind too, if you have no access to 3ph then a 1ph to 3ph converter will knock you back about 700 quid for a 3kw motor otherwise its a hell of a lot cheaper to buy a 3phase motor.
Sorry i havent got one.

 

[bcm_spark]

Thought I was, I don't know where I got that from. I don't get along much with the theory nowadays, bending conduit and fitting tray and basket is all im good for.

 

[boatnik1]

Depends what the motor connections are and its duty. If it's a star delta motor that can run 380/440v connected star and 220/230v connected delta, you can run it on single phase on 230v delta with run capacitors between two phases and the 230v connected to the spare phase and one of the other two. Ideally a start cap should be fitted through a switch and paralleled with the run caps, the start cap should be switched out when the motor runs up.. Power output will be reduced but if you can start the motor on a light load and it doesn't need the full KW it'll run OK.

 

[Darkwood]

Depends what the motor connections are and its duty. If it's a star delta motor that can run 380/440v connected star and 220/230v connected delta, you can run it on single phase on 230v delta with run capacitors between two phases and the 230v connected to the spare phase and one of the other two. Ideally a start cap should be fitted through a switch and paralleled with the run caps, the start cap should be switched out when the motor runs up.. Power output will be reduced but if you can start the motor on a light load and it doesn't need the full KW it'll run OK.

Well i must agree but from the basic question he asked thought it might be too complicated for him to go down this road he could prob pick up a cheap second hand motor as a easier option than creating phase lag with capacitors but must agree did misunderstand his shorting two phases out question but you never know he may have a american motor star/delta so hes got the option to convert, slightly embarrased i missed that thought.

 

[boatnik1]

Darkwood:
I was thinking it was just an intrepretation of what the OP had originaly missunderstood.
Most low Kw motors to Euro spec are wound as either star or delta giving the option of 3ph. 220 or 415 . not just US motors. An inverter would be another option without going the full converter route.
New 3Kw 1ph motors are available but quite expensive and don't often appear on the used market.
For anyone with a small workshop a 220v 3ph rotary converter is easy enough to make up and allows the running of 3ph lathes/mills etc which are more plentiful and cheaper than the single phase versions.

 

[Andy Smith]

A new motor or an inverter is the best answer. Messing around with capacitors across phase could be complicated and most definatlty going to cost long term unless you have good power factor correction as well. All the best