DIY 3 phase convertor info wanted

[graduate_owner]

Hi everyone,
Has anybody tried making their own single to 3 phase convertor? Or has anyone bought the plans from Desert_Daves_Toolbox ebay site - are they any good or are they just what you'd find on the web anyway?
I've been looking at prices of convertor kits from drives direct and although much cheaper than ready made items, there does not seem to be much in the kit for the £200+ they are asking. So I'm thinking to go may own way but need to size up the components, hence the Desert_Daves_Toolbox plans.

K

 

[nev]

I think that 9fingers (Bob) would be the man to speak to , alas no longer active on this forum , but if you search for his name his signature has some contact details, as well as a very handy link about all things motors....

below is copied and pasted from a previous post of his

Bob

_________________
I'm no longer active on this forum. If you want to contact me try [email protected]
Information on single and 3 phase induction motors http://homepage.ntlworld.com/bob.minchi ... Issue2.pdf

 

[graduate_owner]

Thanks Nev, I've already heard back from Bob Minchin with a suggestion for a book on the subject, so that may well get me started. I am still trying to find time to call in Foelgastell to visit (typical, no time for anything when you've retired)

Keith

 

[graduate_owner]

I forgot to say, the book Bob recommended is model engineering series No 47
"Three-Phase Conversion" by Graham Astbury ISBN 978 185486 262 4 first published 2010. I think that was the most rapid response I've ever had.

K

 

[Andy RV]

Have a look here;

http://www.practicalmachinist.com/vb/tr ... rters-vfd/

I've done some very brief research and they seem quite easy to make, the hardest party is probably sourcing a suitable transformer if you need to bump the voltage up to 415v.

 

[SammyQ]

Having several three phase motors (cheap!) and done the research, then executed the practice, I will bludgeon my way in and say:

The 'Murricane website posted above is fine, but they mix 110/220 Volt chatter - very confusing for us Brits on 'proper' lecky. They are also deeply infatuated with rotary converters, which increases your electric bill (two motors running, not one) and can be VERY noisy.

The cleanest, best, most satisfying method I've used is: whip the bell-end off the motor :shock: (Frankie Howard, come back...) expose the triple point, rewire to 240 Volt configuration, reassemble, buy a nice silent 240V/3ph converter off Ebay, live a happy life in relative peace and quiet, muttering "brush motors are for masochists!".....

Sam

 

[graduate_owner]

Hi SammyQ,
that was an interesting comment - BUT how do you recognise the triple point, and how do you know what to do with it when you've found it? I would really like to be able to avoid finding/rewinding a transformer to get 415V. I think the rest should be fairly straightforward, from what I've been reading (3 phase conversion by Graham Astbury, plus loads and loads of web research).

K

 

[SammyQ]

It's a bit late now, but I have a pictorial essay somewhere on me hard drive (from OWWM I think) details it summat perfect. I'll ask Howard Carter to resurrect it and then either post it here or PM it to you. Essentially,you separate the three wires in the triple point, bring 'em out via extensions inside heat-proof tubing to the connections existing, then top'n'tail them alternately!

Sam

 

[SammyQ]

Try this: http://bbs.homeshopmachinist.net/thread ... tor-rewire

Guy's a genius.

Also, in the same vein, but not as clear:

http://madmodder.net/index.php/topic,77 ... l#msg83157


YOU WLL STILL NEED A CONVERTER! But, the motor will now run on 240v supply, the converter electronically creates three phases.

Sam

 

[graduate_owner]

Right, so my approach is going to be

try to change the motor from star to delta (unless it is already dual voltage, which I doubt). It's in the back of a colchester lathe at the moment so I haven't been able to check it over yet

build a static phase convertor using capacitors, based on the info in my book, and no need to bother with rewinding a transformer. That will probably cost somewhere around £100 - £150 I suppose, just top of the head figures based on the fact that a bought, ready made static convertor is about £400. I will then be up and running.

possibly try to get hold of a 4HP 3 phase motor at some time in the future so as to convert the static into a rotary convertor.

Thanks guys for that info on motors, with any luck it has made the whole job a lot easier.

K

 

[SammyQ]

K? A 240V/single phase to three phase converter will do the same job as a static converter? There are some nice ones coming out of Hong Kong on Ebay these days and for money similar to your capacitor shopping list.

Sam

 

[graduate_owner]

After further reading of my book, it seems that building a convertor to work at 220V is not a good idea - the book says 'expect to be disappointed if you try this on a delta wired motor'. So I'm now thinking to go for an inverter. I already have a 2HP inverter so I'm familiar with them. I'll still need to change the motor to 220V because a 415V inverter is about double the price.
I'm not sure about an imported one - Chinese machinery etc doesn't fill me with confidence and I'd rather pay the extra for one bought from the UK with a guarantee.
The issue will then be to sort out the wiring to the lathe, hopefully so that the original switchgear can be kept intact.

|First job though - get the lathe.

K

 

[wizard]

I looked at a rotary phase converter when i bought my wadkin saw a few weeks ago i was going to buy it until he started it up then i was not sure then when he started the saw i was right of it then he said it needed a 30 amp supply, i just bought the saw.

 

[MMUK]

If you want a decent, quiet running inverter you won't go far wrong if you can pick up an ABB one