convert 3 phase motor

[Department71]

I have been offered one of those big boy log cutters with a huge circular blade, the only problem at the moment is that the saw motor is 3 phase and I only have a single phase supply. Would it work if I just use one of the phases on the motor, ie connect the live to one of the round pins. I take it the rectangle pin is the neutral.

I have an electric chauffe eau that can be wired for 3 phase or single phase and that works ok on my single phase supply, so I am hoping I can get this saw to work on my single phase supply. I have knowledge and am happy to work on single phase, but have little experience of three phase.

Any help appreciated.  Steve

[crossy67]

Can't run 3 phase motors on single phase sorry. You can buy an inverter to convert single phase to 3 phase though but they are not cheap.  We used to use Mitsubishi ones, they were quite good.  A quick ebay search shows between £175-400, depends on the size of the motor, rule of thumb 750w = 1hp.

http://shop.ebay.co.uk/?_from=R40&_trksid=p3907.m570.l1313&_nkw=3+phase+inverter&_sacat=See-All-Categories

You would be able to buy a single phase motor for less.

[Gluestick]

You can in point of fact run a Three Phase Electric Motor on Single Phase: what you cannot do is get the damned thing to start properly!

Since Single Phase Induction Motors are now reasonably cheap, suggest you evaluate swapping the motor.

See here:

[Jonzjob]

Funnly enough, I have just uprated my lathe from a single phase motor to a 3 phase motor via a 1 to 3 phase converter from a company called Drives Direct. Their converter is the dogs whatsits. Just google 'drivesdirect uk' and there is a load of info on there!

[Department71]

Thanks for the replies, will look into this further when back in the UK. The motor is I have been told is 4hp, it goes like a jet engine, think 2hp will be enough, but will be bringing it home with us. Wonder if I can get it rewound.

Steve

[Dave&Olive]

hi ok

             Just make sure you have enough amps to power a big single phase motor ???

 a 4 horse single phase motor is a big engine

                 Dave

[Araucaria]

[quote user="Department71"]Thanks for the replies, will look into this further when back in the UK. The motor is I have been told is 4hp, it goes like a jet engine, think 2hp will be enough, but will be bringing it home with us. Wonder if I can get it rewound.

Steve

[/quote]

Steve - the cost of getting its motor rewound might well exceed the cost of getting a three-phase supply installed (or reinstated) on your property. You'd then have the ability to run all sorts of wonderful kinds of powerful electrical gadgets. We had to have a three-phase supply installed (for a quoted charge from EDF of €120, which they never in fact billed us) to run our wood-fired boiler.

[Department71]

Back in the UK and been having a look at various options for the motor, one amendment I need to change here, I don't think it is a 4hp jobbie as I was told, the Kw stated is 2.94 on the plate.

Now options, there are 2 and 4 pole motors on offer, the 4 pole ones spin at about 1500rpm and the 2 pole about 3000rpm. The 3phase one I need to change spins at 1420, but the log cutters I see advertised spin in the high 2000+. Would there be more "grunt" in the motors that spin at the lower speed? I appreciate the motor I'll be getting will be a bit smaller then  the 3phase one, was looking at one in the region of 2.2-2.5kw.

 Any thoughts from the experts.

Araucaria, not worth getting a 3phase supply reconnected, extra cost not worh it, plus shmbo hasn't got a 3phase kettle!

Steve

[Théière]

Generally speaking the more poles the more torque you get at lower rpm, hence the need for the 2 pole motors to spin faster to achieve a similar result. The cutting speed you require is based on the peripheral speed of the blade i.e. per tooth and therefore I would stick somewhere near the original rpm or risk overheating the blade and ruining it

[La Guerriere]

2.94 kW is about 4 HP, but the starting current will be substantially more.