Single to 3 phase conversion & motor tutorial.

[9fingers]

I am starting to give some thought to how to do this so that it is both useful to the non- techy as well as providing some background understand for those who want to know "why" as well as "what to do"

I don't want readers to be put off by the detail such that they think they can make use of the modern devices that technology has provided.

Several of you have asked for this so firstly I want to make it useful to you and very much secondarily to save me writing similar stuff over and over on the forum and in PMs

My first thoughts are to write a "how to" first and provide links to more information (the "why") for the curious.

I'd welcome ideas on a structure either in open forum or via PM

I plan to start with a simple section on the types of motor we find in our workshops especially brush and induction (both single and 3 phase) motors as well as some basics on electricity eg what does single and three phase mean.

I know for many woodworkers, maths can be a challenge so I will try to keep this to the very minimum and then mainly in the "why" sections

I'd also like to hear the generalised questions that you would want the tutorial to answer.

So please give me some feedback on what YOU want from this turtorial.

Regards

Bob

 

[wizer]

I just wanted to add my support Bob. I think it will be a very useful resource.

 

[OPJ]

I'll second what Tom has said. Make sure you include many photographs and hopefully it could be made in to a 'Sticky' at the top of the forum.

 

[head clansman]

Hi

as bob knows I'm trying to go down this path at the moment even if i don't win what I'm watching , I'll try again till i do get what I'm after so i want to know just what is involve in changing a motor from 3 phase to single phase so do tell all, plenty of pics as well please sizes of motors in relation to blade size etc, every thing .hc

 

[9fingers]

Having your support is very encouraging but I would really like some guidance on what folk need to know.
It would be a shame if I spend time writing up what is already common knowledge and miss out the burning issues. :roll:

Bob

 

[RogerS]

Bob

Firstly it's a great idea. For my two penn'orth I'd suggest that basics such as the difference between single phase and three phase is done later. Same goes for brush motors and induction motors. Brush motors are noisy. Induction motors aren't. I would argue that from a woodworkers perspective - at the top level - that that is as far as it goes on that topic!

I think that for us woodworkers what we'd appreciate is information on the practical side of buying and using three phase in a single phase world.

Maybe something at the top level as simple as pro's and con's.

Such as:

1/ How to get three phase

- pay for and install a three-phase supply. Upside - limitless (give or take) 3-phase. Real 3 phase as opposed to ersatz 3 phase from converters. Downside - possible cost. Have to use an electrician. need detailed power loaing requirements up front. Much more complicated as lots of red tape and paper work

- static converter. uses one winding on the motor to generate the third phase (am I right there?). downside - have to watch the voltage before you switch on and when actually doing any woodwork. If your personality is wanting to get things on the nail then you'll end up watching the voltmeter and not the blade = blood. Does the static converter need to be turned on all the time or only switched on when you want to use your machine. What is the 240v power requirement aka thickness of cable. maybe table that relates say a sedgwick planer/thicknesser power reqt against size of static converter against size and length of 240v feed cable. one woodwork machine on at a time

rotary converter - more expensive that static. Self-adjusting (is it? or is it close enough not to need to worry). multiple woodworking machines can be used etc etc

inverter - not quite sure what that is in relation to 3 phase. I know about 12v to 240v inverters.

replace the motor - most motors have standard fittings ??? what else is involved??

That sort of thing.??

 

[wizer]

I know nothing about the entire subject. So anything will be of interest. I think you need to look at it from a woodworker who is going to buy an old 3ph machine and convert point of view.

 

[Rknott2007]

I'm not sure if this comes into the catergory but how about info on how to prep a new workshop for power before its been built or during?

 

[RogerS]

I'm not sure if this comes into the catergory but how about info on how to prep a new workshop for power before its been built or during?

I think that is a topic for another day. It's almost in the category of 'how long is a piece of string'.

 

[head clansman]

hi

I would like to know everything about this , so why not start at the very beginning and do it in say chapters, each chapter marking each step as you see it, that way we can all get to follow it at our individual level of knowledge .

P's but get the mods to place it as a sticky for all to see permanent.

 

[plymouth pirate]

Electricity is a fascinating subject and one I never really got my head around when doing my MN engineers exams. We were subjected to theories of magnetism and electronics, which we really didn't need to know to do our job as engineers. That caused me more confusion than enough and a lot of time was wasted in trying to understand it.

I think that, to start, it would be easier to explain and give examples of the various things that make a woodworking machine tick such as the most common stop/start wiring circuits, microswitch use and settings, NV breakers, the wiring of single phase motors and the reason for capacitors and centrifugal switches on them, then build from there.

Regards
John

 

[9fingers]

Thanks for the useful suggestions that are coming through.

Could i ask a favour please. I don't have any machines with high power brush motors. I hate the things but that is just my prejudice!

Please could people send me some photographs of machines such as table saws with brush motors on; ideally a view that show the access screws for the brushes.

Please email these to bobdotminchinatntlworlddotcom

Thanks

Bob

 

[RogerS]

I really feel that we are in danger of trying to encompass the entire world corpus of knowledge on electricity. A lot of what is being requested is readily available on the internet..for example, wikipedia.

What isn't so readily available is how to run 3 phase machines on a single phase supply from a woodworkers perspective.

 

[wizer]

I really feel that we are in danger of trying to encompass the entire world corpus of knowledge on electricity. A lot of what is being requested is readily available on the internet..for example, wikipedia.

What isn't so readily available is how to run 3 phase machines on a single phase supply from a woodworkers perspective.

agreed

 

[studders]

Having your support is very encouraging but I would really like some guidance on what folk need to know.
It would be a shame if I spend time writing up what is already common knowledge and miss out the burning issues. :roll:

Bob

I'd like to know, explained in simple terms, how motors do what they do. Frinstance, I can't get my head around why a certain voltage motor can't be used with other voltages, why or how they turn a certain way and, can that be changed, what makes one motor 1/2 HP and another 3/4 HP? :?

 

[slemishwoodcrafts]

Hi,

this might fall into the category, but I would like to know about wiring motors up to starter switches etc and methods of variable speed control.

regards,

michael

 

[SammyQ]

Bob, I suspect I am in the position of many here - I have a single phase wired workshop, but have managed to buy, cheaply, some three phase machinery. Our problem is:

"How do we run three phase on a single phase supply?"

RogerS pinpopinted our problems: a) What are the differences/advantages/cons between static/rotary/a.n.other way of emulating three phase off single and b) how do we wire them up?

I have read the two excellent model engineering texts by Jim Cox and confess to having stalled as soon as I opened the terminal box on my stonking big ('old') three phase floor drill...."there has to be a simpler understanding" I told myself. I cheated at this point by buying an inverter, but it cost a whopping amount and THAT was after combing Ebay feverishly for eight months to find a barely affordable one.

Now, I am an ex-member of MENSA, have a good degree and have rewired two houses during renovation, so inability and inexperience don't feature here. What does is CLARITY and simplicity. I second the call for "How to" now and "Why it works? later.

Sam, feeling VERY grateful that you have offered to do this.

[/u]

 

[ivan]

I would have thought the Cox's 2 books on electric motors (eng workshop books series) would have said everything, but apparenttly not for very old drills! A good place to start, though, and saves you an awful lot of typing.

 

[RogerS]

I would have thought the Cox's 2 books on electric motors (eng workshop books series) would have said everything, but apparenttly not for very old drills! A good place to start, though, and saves you an awful lot of typing.

Spot on, Ivan. And Wikipedia has loads of stuff already. For example, http://en.wikipedia.org/wiki/Electric_motor.

Digressing slightly but in the 3 phase vein, had a couple of lads from EON Central Networks call by investigating some nuisance tripping we've been having on our incomer. I asked if they knew how much it would cost to run a 3 phase circuit to the workshop. About £5000 was the guesstimate. For a start, the smallest size 11kV > 415v 3 phase transformer costs £3500. I also asked if they'd instal it as an overhead but they said not as the distance was so short, they would run it underground.

 

[SammyQ]

I think the problem with Cox I and II is that - as he himself says at two points - there are exceptions to every 'rule' and electric motors seem to have a plethora of idiosyncratic builders. No doubt a sparkie, with daily experience, could suss out the rudiments when presented with an unusual layout. I, on the other hand, am more at home with clades, Ψcell and T helper lymphocytes and confusing wiring has me in dread of starting a fire in my hard-won Man Cave.

This thread started with an offer by 9fingers/Bob to serve up a tutorial of "monkey-see, monkey-do", followed by an explanation of why there were three electric monkeys...? Yes please Bob, this duffer needs help, more or less as RogerS spelled it out earlier:

What isn't so readily available is how to run 3 phase machines on a single phase supply from a woodworkers perspective.

Sam