Single to 3 phase Conversion

Sir Osis of Liver.

A friend is looking for a way to run a 7hp 3ph motor on a lathe using a single phase supply.
Its in his workshop/shed but he doesn't have a 3ph supply and not much to spend.

Can it be done cheaply and safely?

Any suggestions lads?

brightspark

What do you mean by not much to spend.

An inverter for 5.5kw won't be cheap.

A quick look on Radionics found this

http://radionics.rs-online.com/web/p/inverter-drives/0104537/

At €930!

Not that I'm saying it will be suitable without knowing more details!

Also is there an adequate power supply available?

Who is going to wire it up?



I doubt if cheaply and safely is possible

Sir Osis of Liver.

That's a bit costly,but thanks for the reply.

brightspark

Maybe someone else has a better idea?

solargain

Have a look at the schneider range of Altivar http://www.schneider-electric.com/products/ww/en/2900-motion-drives/2905-compact-drives/2656-altivar-312/

brightspark

solargain wrote: »

Have a look at the schneider range of Altivar http://www.schneider-electric.com/products/ww/en/2900-motion-drives/2905-compact-drives/2656-altivar-312/

The one I linked to was an Altivar also.

solargain

You might get a better price from the wholesalers

frankmul

There will be power output loss dropping from 400 3 phase to 230 3 phase.

brightspark

frankmul wrote: »

There will be power output loss dropping from 400 3 phase to 230 3 phase.

Yes, unless the motor has 230V delta / 400V star windings, some do.

But I did say that the suitability of the inverter depended on knowing more details.

regardless, with an inverter alone costing in the region of €900, before purchasing suitable circuit breakers, installing an adequate power supply, and modifying the control circuit of the lathe (some of the control circuit may be currently using 380V coils) etc., I doubt anyone would call the project "cheap"!

frankmul

Would a better option be a single phase to three phase converter?
http://www.boost-energy.com/phase-converters/the-range/a-6-kw
I don't know a lot about them

2011

frankmul wrote: »

There will be power output loss dropping from 400 3 phase to 230 3 phase.

If the OP were to operate 3 phase machinery on a 3 phase 230V supply rather than a 3 phase 400V supply the output from machines would be very much reduced. Is that what you mean?

However if the OP were to use an inverter it would make sense to use one that has a 230V single phase input and a 400V three phase output.

tomdempsey200

i thought the 230v 1P input inverters were only 230v 3P output.. no?

and that the motor would have to be dual voltage as in post #9

i don't know too much about them

frankmul

I thought the same as tomdempsey200. I have see a few single to three phase inverters and the output was only 230 3 phase. I think to get 400 volt 3 phase you have to use a converter, a motor/generator combination? I have never see one so I'm not sure how good they are.

Steve

2011 wrote: »

If the OP were to operate 3 phase machinery on a 3 phase 230V supply rather than a 3 phase 400V supply the output from machines would be very much reduced. Is that what you mean?

However if the OP were to use an inverter it would make sense to use one that has a 230V single phase input and a 400V three phase output.

Most if not all inverters can't increase the voltage - so 220 1~ in = 220 3~ out.

The question is can the motor run on 220/3~ ? i.e can it run in delta 220? if so then an inverter will work.

2011

Steve wrote: »

Most if not all inverters can't increase the voltage - so 220 1~ in = 220 3~ out.

The question is can the motor run on 220/3~ ? i.e can it run in delta 220? if so then an inverter will work.

...here we go, 230V single phase in and 400V three phase out:

http://www.boost-energy.com/phase-converters/the-range/a-6-kw

darragh o meara

Probably easier to get a new single phase motor. I've seen it done in the last and whereas you won't get exactly the same grunt as before it will work, and safely at that too.

Steve

2011 wrote: »

...here we go, 230V single phase in and 400V three phase out:

http://www.boost-energy.com/phase-converters/the-range/a-6-kw

£921.00 (ex. VAT)

A new motor would be cheaper

Bruthal

frankmul wrote: »

I think to get 400 volt 3 phase you have to use a converter, a motor/generator combination? I have never see one so I'm not sure how good they are.

The ones that step up use a step up transformer to supply 400v single phase to the idler motor which generates the 3rd phase, giving 400v 3 phase.

2011

Steve wrote: »

£921.00 (ex. VAT)

A new motor would be cheaper

Yes, but if you read back you will see that my point was that if the OP is going to go down the 3 phase route (with an inverter) then it would would make sense to go three phase 400V rather than three phase 230V. Either way it would not be cheap.

Ghost Train

My understanding is if it's a 415v motor and you have a 230v drive you can use it up to about 32hz, so you're losing 33-50hz

Here's some more 240v to 415v drives
http://stores.ebay.co.uk/drivesdirectinvertersltd_W0QQ_fsubZ5

Sir Osis of Liver.

darragh o meara wrote: »

Probably easier to get a new single phase motor. I've seen it done in the last and whereas you won't get exactly the same grunt as before it will work, and safely at that too.

That was what I suggested aswell ,but there doesn't seem to be anything capable of driving his machine.

2011

Ghost Train wrote: »

My understanding is if it's a 415v motor and you have a 230v drive you can use it up to about 32hz, so you're losing 33-50hz

Where are you getting that information from?

Bruthal

Sir Osis of Liver. wrote: »

That was what I suggested aswell ,but there doesn't seem to be anything capable of driving his machine.

Single phase motors above a kW or so are not much use, particularly with induction ones, as they just won't have much torque. A 5kw one would be impractical in single phase.

2011

Although a variable speed drive is never going to be a cheap option another advantage is that the starting current of the motor can be dramatically reduced. This can be achieved by ramping up the voltage and the frequency.