Electric Motor query - 3 phase/single phase

[OldWood]

I know you are all woodworkers but many of us are general engineers as well so here's an 'OT' but wood working related question.

I'm thinking about getting a planer/thickenesser and paid a visit to a local tool merchant who also deals in second hand equipment. He has a machine that is the right size but has a 3 phase motor of 1.5kW. Now it just happens that I've been given in the last couple of weeks a fairly up-to-date 2kW single phase motor.

Forgetting about the possible mechanical problems of changing the motors over, are there any other characteristics that are likely to cause bother - I haven't looked at motor speeds yet but that is just changing the pulley size. Will I have problems for instance at start up as the planer will have a fair amount of inertia ?

Any comments gratefully received.

Rob

 

[houtslager]

IIRC you have to match the RPM so that the cutting block DOES NOT over rotate.That said if your within 5% no problems.
Get the pulley arrangment right,then the end rpm of the block will be fine, and you'll have the extra Hp to help deal with close knit wood grain and the like.

 

[dickm]

You lucky chap, getting a decent 2kW single phase motor. -they seem to be close to hen's teeth for rarity secondhand. Other than Houtslager's comments, the only thing you need to check is that it is a capacitor start motor. The alternative, split phase design might well not have enough starting torque. That said, most motors of over 1kW probably will be cap start.
And, of course, you will need new switchgear, 'cos the 3 phase beast was probably 415v and needs a lot less current than the single phase one will. Cheapest solution is probably one of the complete start/overload units that Axminster, Machine Mart and others do.

 

[OldWood]

Thanks for your comments guys - fortunately the single phase comes with switchgear and cap. What I don't know is what the start up timer characteristics are; I recovered a similar somewhat older motor from a skip sometime back and had to replace the capacitor and then reverse engineer the timer to get it to run my circular saw.

I'm now swithering about tackling it this way having found that I can get 1.5kW convertors for around £150. By the time I've faffed around with the mechanics and possibly the electronics, let alone bought in pulley wheels, machined them, etc, etc., it might well be £150 worth.

A useful website for this sort of thing I found is

http://www.lathes.co.uk/

Rob

 

[dickm]

had to replace the capacitor and then reverse engineer the timer to get it to run my circular saw.

I'm now swithering about tackling it this way having found that I can get 1.5kW convertors for around £150. By the time I've faffed around with the mechanics and possibly the electronics, let alone bought in pulley wheels, machined them, etc, etc., it might well be £150 worth.

Well, if you were thinking this way, I'd happily relieve you of the 2kW single phase motor!!
Seriously, I'd be surprised if you had to do anything other than change the pulley, and that will almost certainly be a standard bore, so no machining involved. Unless, of course, the P/T has a very specialised flange, rather than foot-mounted, motor. But you'd get a lot of pulleys for £150.
I've no experience of 3phase converters, but have heard doubts about the cheaper ones. Mind you, there was a piece in an old FWW about using 3-phase motors on single phase by manually starting a larger 3-p motor and using it as a generator. Not a good idea, but I have tried it and it works!