3 phase electric HELP

[thinfourth2]

cqueen said:

love it

Think I'll just buy a 3.5hp converter and see what happens.

It will go bang or not work

Read what i said about control circuits

Also if there is a control box which will be a box full of controls.

normally identified by being box shaped and a removable cover.

Remove the cover and look for pieces of paperwork as the old fashioned way of doing things was to stuff a wiring diagram in there. If no paperwork or diagrams then take a picy of the bits inside

ETA

Looked at the cheesefest video and below the buttons is the control box which is opened with a key look in there

Edited by thinfourth2 on Monday 12th September 11:06

[cqueen]

thinfourth2 said:

It will go bang or not work

Read what i said about control circuits

Also if there is a control box which will be a box full of controls.

normally identified by being box shaped and a removable cover.

Remove the cover and look for pieces of paperwork as the old fashioned way of doing things was to stuff a wiring diagram in there. If no paperwork or diagrams then take a picy of the bits inside

Edited by thinfourth2 on Monday 12th September 10:55

Why would it go bang? Yes there is a control panel and some paper diagrams, but im not at home right now so will post them later. Thanks

[cqueen]

thinfourth2 said:

Answer the question about are the motors individually switched as it is important.!

Yes the motors are separately controlled. Most of the time only 2 of them will be in use, sometimes all 4

[thinfourth2]

You have 4 separate motors starting and stopping. A 3 phase motor takes a HUGE amount of current to get up to speed due to the way they work with spinning fields etc. Think of a car which is stuck in 5th you need a lot of revs and clutch slipping to get it going.

A digital converter does things completely differently. It starts at 0Hz and slowly ramps up to 50Hz so you aren't trying to accelerate the motor up quickly so you draw a steady amount of power instead of a big peak.

If you plug into a digital converter and push go it will start to ramp up to 50Hz 220V (to earth 440V across the phases) this will give your controls the juice. You will push go on your first motor it will connect directly to the 50Hz and will draw a big load of amps and your converter will see this and either scream over current and sulk or blow-up or if you are lucky be okay.

I would be looking inside and seeing what powers up the controls, probably a 440V to 24V transformer. Bin the transformer and replace it with a 240V to 24V transformer and run this off one plug.

Then find the 4 main motor contractors and bin them. Replace each one with a 0.5Bhp inverter with a shared 240V feed which will be on a second plug.

But i haven't seen the wiring diagram yet

[cqueen]

So why would this be different to a lathe or big saw in someones domestic workshop? Can't i just buy a converter that is powerful enough to cope?

[freecar]

A big lathe is usually one motor and that's it, maybe a coolant/slurry pump but not much else.

3 Phase is made of 240V supplies, so some parts may only use one phase and therefore run on 240V some may use all phases and need 440V, if you just try to run 440V through the whole thing it might fry the bits that were only wired for one phase.

I used to QC hugs aircon units, the three phase ones could still have a single phase elements inside, they all differed depending on customers need.

Best thing to do would be to get a spark and a full wiring diagram of the unit from the factory, that way the spark will be able to convert it properly for use in a domestic (single phase) setting.

[thinfourth2]

cqueen said:

So why would this be different to a lathe or big saw in someones domestic workshop? Can't i just buy a converter that is powerful enough to cope?

You can buy an inverter that is big enough to cope. As you are looking at 4 x starting current for all 4 motors in a worse case sernario

However 4 small inverters maybe a cheaper and better solution.

The inverter i have for running my coolant pump was about £60 and it is not much bigger then a pack of cards.

This inverter gives me speed and direction control.

The inverter for my lathe motor gives me ramp up, ramp down, direction, speed, inching and emergency braking controls options. If i was to run it off 3 phase i would have direction control and nothing else.

A digital phase converter is far smarter then a simple stop go

[B160 AVE]

Just get a sparks in fella

We fit single and 3 phase condensing units (2-3.5hp) and it is possible to wire a 3 phase unit into a single phase supply (but not the other way round!), provided you know what you`re doing, takes the boys about an hour and a half.

Good luck

[cqueen]

I stopped by an electrical supplier/contractor earlier, he recommended a local company that would re-wire all the motors for probably less than the cost of the converter. I'll pop down there later and see what they say. Sounds good though!

[freecar]

cqueen said:

I stopped by an electrical supplier/contractor earlier, he recommended a local company that would re-wire all the motors for probably less than the cost of the converter. I'll pop down there later and see what they say. Sounds good though!

this is the best idea. Lots of things are wired in three phase for packaging reasons not because they need the specific voltage. You might find that as all his other machines were 3 phase it was easier to get three phase versions of everything, they are sometimes cheaper too!

It could be as simple as fiddling with the wiring and you're all up and running!*

• Of course I mean get a qualified spark to fiddle with the wires!

[cqueen]

Hmmm I've just spoken to a couple of electrical motor engineer types, the both said 'mmmmeh, you'd be better off just buying a converter'. Although I kinda got the impression they just weren't really interested in the work.

[jason s4]

cqueen said:

Hmmm I've just spoken to a couple of electrical motor engineer types, the both said 'mmmmeh, you'd be better off just buying a converter'. Although I kinda got the impression they just weren't really interested in the work.

The trouble with commercial/industrial electrical is that most of them probably wont be interested in "little jobs".

Which is why you are better off contacting a local one man band type.

Have a look here:

http://www.competentperson.co.uk/search.asp

[cqueen]

some more photos...



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[sjj84]

Have you looked into the option of replacing the motors with 240v single phase ones and having the control panel rewired?
Looks from the pics like the control circuit is 24v, can you take a better photo of the Siemens item so it's possible to read the details on it?

[jeebus]

If that machine has a gas powered burner inside you are also opening another can of worms with regards to the gas regs, if you was to start altering the internal wiring you would also be altering the saftey devices/circuits for the gas side of things. From the pictures you have posted I would suggest getting either a single phase machine or a three phase supply.

[cqueen]

Any good?



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[sjj84]

At the top are there just two wires? One connected to 2 and one to 4?

[cqueen]

sjj84 said:

At the top are there just two wires? One connected to 2 and one to 4?

Not sure what you mean, could you expand?

[cqueen]

A little futher info. I wont have all 4 motors starting at the same time.

I will start motor 1 and that will run constantly, then 5mins later start motor 2. Then 10mins later I will turn off motor 2, but will instantly turn on motors 3 & 4 together.

So max of 2 starting motors at one time and most likely no more than 3 running at any time.

[sjj84]

cqueen said:

Not sure what you mean, could you expand?

The Siemens unit, at the bottom as can be seen in the picture you've got two wires coming out which are marked up as 24v, what is going into the top of the unit?