single phase or 3 phase ????

[chrisf1]

Hi again everyone I have been looking at a compressor that the owner says is single or 3 phase, he tells me that the wiring just has to be changed as it is running 3 phase at the moment he has sent me a picture of the label that I will attach to this. My question is, is this possible or is this an alternative wiring if single phase motors are used, he is of the impression that the motors themselves are dual single or 3 phase can anyone enlighten me on this. Thanks Chris

 

[madkayaker]

that is a duel voltage 3ph motor so could be run with a converter (static or rotory) or with an inverter

 

[chrisf1]

I take it that means an inverter would have to be bought then and would not already be part of the motor set up thanks Chris

 

[madkayaker]

that's it an inverter big enough is not going to be cheep

 

[eddie49]

The owner is wrong. The motors are three-phase and that's it. The internal windings and construction of the motors specify that. But, as mk says, the motor windings can be linked to run on either 415V Star ( "Y" ) or 220v Delta, 3-phase in either case. The latter is what you would get out of a single-to-three phase converter or inverter. However, to cope with the start-up current of compressor motor(s), this would be large and/or expensive, and it would require a very beefy single-phase supply.

 

[piman]

Hello Chris,

to give you an idea, there's a company advertising 240 single to 240v three phase invertor, 3 H.P. for £225.

Alec

 

[chrisf1]

Thanks for the replies I will steer clear of that one cheers Chris

 

[madkayaker]

you could swap the motor if its cheep enough

 

[chrisf1]

The price is wrong for me if I have to spend more on it he believes or so he tells me it is simple rewire thanks anyway Chris

 

[Highway_Star]

That one is along the road from me, and I too do not believe it is single phase, dual voltage 3 phase eddie49 says. For the kind of money you'd spend to get it running, you'd have comfortably bought a new compressor.

 

[madkayaker]

whats its item number

 

[Highway_Star]

200475568406

 

[madkayaker]

bit to far away for me and a bit rough

 

[piman]

Hello Chris,

"so he tells me it is simple rewire "

It's probably the fact that it says 240v on the nameplate, and he's assuming that means single phase?
That's a charitable explanation anyway?

Alec

 

[brightspark]

Hello Chris,

to give you an idea, there's a company advertising 240 single to 240v three phase invertor, 3 H.P. for £225.

Alec

the invertors are rated 3hp but arent suitable for starting compressors under load

 

[brightspark]

the motor states 415v or 240v 3 phase dual voltage not single phase . meaning it will run on a converter either star conection at 415 v or 240v delta conection its a bit misleading people thinking it can be run of single phase with just altering a few conections but not the case

 

[piman]

Hello Brightspark,

rated at 4.5H.P. surge.
The other factor with inverter drives is the ability to programme the start characteristics. For example we installed one for our peristaltic pump which needed to do about 30 starts per hour (2 KW motor ). Due to the pump type they are harder to start than centrifugals; by programming the start we can do this without overheating the motor.

Alec

 

[madkayaker]

The seller has adjusted his listing

 

[Omniata]

Judging by the rest of the pictures in the listing I'd steer well clear...

Something like that, in that condition really will cost you more in time and effort putting it right...

 

[Luke]

Crikey, why all the hysteria against inverters? suitably rated they will do the job fine, and if the comparative machine costs allow, they aren't always an 'expensive' solution.