phase converter

[russ_1380]

Hi everyone.

I have an old pillar drill lying around that I need to get working. It is 3 phase but I only have a single phase supply.

I took the motor off and have taken it to numerous motor specialists. It is looking more likely that it will be easier to get a phase converter rather than trying to source a similar single phase motor.

The main problem being the physical size of new motors, the ones the specialists showed me are far bigger than the original al look cheaply made. It probably would be possible to adjust/weld new mount brackets up to accept a modern motor, but i would also need to bore out the pulley or slim down the motor shaft t make the parts fit. I do not have access to a lathe and can't really be bothered faffing with it.

So, my questions are; what is there to look out for when buying a phase converter?

The motor bloke said my 3ph motor can run at 250? or 450 volts 3 phase, but needs rewiring to change the voltage.

Is a phase converter a worthwhile investment? I will possible end up buying a 3 phase lathe in the near future.

Is it as simple as plugging a 3phase socket in the converter and then plugging in the converter to single phase domestic socket? I imagine it is not?

Any help appreciated

Russ

 

[Digit]

What does it say on the motor commissioning plate?

Roy.

 

[9fingers]

Is it as simple as plugging a 3phase socket in the converter and then plugging in the converter to single phase domestic socket? I imagine it is not?

Any help appreciated

Russ

Almost that easy.

Try reading my paper referenced below for lots of background info

Bob

 

[CHJ]

Russ have a read of the Induction Motor tutorial. It's a sticky at the top of the forum.

Unfortunately the link is currently broken but I have taken the liberty of putting a copy on my server until such time as Bob (9fingers) gets time to sort it.

Alternate Link to File

 

[9fingers]

Thanks to Chas for pointing this out.

I 'think' it is all fixed now.

Bob

 

[russ_1380]

Thanks guys, I shall have a read.

I'll get the details of the motor plate for you too.

If I do invest in one, i'd like to be able to run a lathe off it in the future. What kind of hp requirement should I look for considering the possibilty of a lathe?

I read somewhere that when looking at hp capacity for phase converters you effectively lose some hp? ie. a 3 hp capacity machine may only supply 2 and a bit hp to the 3 phase machine? Is this just a myth?

Thanks

Russ

 

[9fingers]

Most converters have a number of stepped settings and approximate the needs of the driven motor. It is better to have some extra capacity in the converter so that you can try a couple of settings - one above and one below the motor rating.

This leads to the suggestion that you make.

If you buy a rotary converter then the adjustment is usually automatic but it is still worth having say 25% more capacity that the biggest motor that you have or plan to have in the workshop.

A rotary converter is essential if you have a machine with more than one motor eg a cutter motor and a feed motor.

hth

Bob

 

[russ_1380]

Cheers Bob

That makes sense. You've probs guessed already that my technical knowledge with electronics is somewhat lacking

I shall do some homework before purchasing. There seems to be some good deals on a certain auction site with 'buy it now' prices. I can't help but wonder why these are so much cheaper than ones from Machine Mart?

Is it because they are an inferior quality or are MM just over priced?

 

[9fingers]

The market leader are Transwave. They have been in the business for years and are very helpful to deal with. They have a website with lots of guidelines on too.

Maybe the cheap ones on ebay are refurbished perhaps?

I've looked at the circuits of the MM ones and there is nothing wrong with them but I do not know what design margins are built into their choice of components. Converters are high voltage, high current devices and need to be well designed and built.

MM have a big chain of shops to support so overheads are higher than the typical Ebay seller.

There are lots of inverters for sale on ebay (see my paper for the difference) from what you have said so far a CONVERTER is what you need.

hth

Bob

 

[cambournepete]

Nick Agar had a used three phase converter for sale at Yandles today.

 

[OldWood]

Russ - I can't remember if Bob points it out in his monograph, but in general it seems that an 'inverter' tends to mean one of the electronic boxes that are committed to one machine - wood turning lathe, etc and are particularly good at giving variable speed. In general the less expensive ones give out 240v at 3 phase. ''Convertors' are either either motor/generator (alright alternator for the pedants!) or a capacitive phase creator - as Bob says these are suitable for multi motor configurations.

Again Bob's paper explains the two wiring configurations for 3 ph motors - the one that needs 415 volts and the other 240. All (?) modern motors can be changed over easily; older motors require the end casing taking off and the coil wires re-connected - I was surprised how easy this was when I did this recently, but then I'm an older generation electronics engineer so go into this sort of thing from a flying start!! If you do want to have a go, I do has some pictures and can 'talk' you through it.

Rob