3 Phase CNC milling machine on single phase

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3 Phase CNC milling machine on single phase

This topic has 13 replies, 7 voices, and was last updated 11 March 2016 at 14:13 by Joe Page.

Viewing 14 posts - 1 through 14 (of 14 total)

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9 March 2016 at 21:45 #229241
Chris Richards 3
Participant
@chrisrichards3
Hello all the electric minded,

So after a lot of searching and saving I have finally sourced a large CNC milling machine that will fit through a 30" wide door. The machine is a Tryax ycm 40 knee mill and uses 3 phase, I now need to convert it to run on single phase.

The machine has a 3 hp motor wired delta, fed through from a small box that appears to have a transformer that states 220v. In it's main cabinet it has a transformer that states input 415v and output 240v. i'm guessing the transformer is just suppling the control that is probably single phase? Maybe I can use the transformer and reverse the wiring, if only life was that simple

At this stage it is quite overwhelming so I need to work out where to start without causing too much damage

I'll try add some pictures, to help explain what im working with, any questions and suggestions welcome.

Thanks,

Chris
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9 March 2016 at 21:45 #15093
Chris Richards 3
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@chrisrichards3
9 March 2016 at 22:12 #229245
Chris Richards 3
Participant
@chrisrichards3
Here's some pictures to illustrate my current observations:

This yellow box goes to the spindle motor

This is what is written on the transformer inside the main cabinet

Main cabinet contents on the machine
9 March 2016 at 22:31 #229247
John Haine
Participant
@johnhaine32865
That big thing with 3 chunky windings looks like a 3 phase transformer to me, but doesn't appear to be the one with the label in the second photo. Could you clarify the photos a bit?
9 March 2016 at 23:09 #229250
Chris Richards 3
Participant
@chrisrichards3
Hi John,

The 2nd photo is a close up of the transformer seen in the 3rd photo. The stamped plate as in 2nd photo says input 415v and output 240v at a current guess it provides the power for the computer and servos but I'm not sure yet until I pull cable covers off.

I'll try get more photos in the morning

Thanks,

Chris
10 March 2016 at 00:00 #229253
Joe Page
Participant
@joepage27051
Hi Chris,

We are all probably going to speculate and without a wiring diagram or seeing it in the flesh we probably can't give you an exact answer. I've worked on a few machines and some transformers step the voltage down to 200/220V three phase which are normally the big machines. With you saying the motor is wired in delta then it must be 240V three phase, so the big transformer sounds like it's stepping the 415 supply down to 240V three phase.

So you could cut out the transformer and stick an inverter in there but you will have to check the power of the control circuits, normally they are powered by single phase, tapped off one of the phases to make 240V. I did also notice 24V on the transformer too which probably is what powers the servos and control circuitry, so if you did remove the transformer you would need an extra supply for the control circuit.

Include some photo's of wires going to and from the transformer, some pictures of the controllers too. Maybe someone close by on here would have a look at it for you,

Regards,

Joe
10 March 2016 at 00:05 #229255
Andy Holdaway
Participant
@andyholdaway
The transformer is a 3 phase auto-transformer. The plate says its got outputs of 55 – 240 volts 3 phase, and it appears to have an auxiliary 24 volt tapping, probably for the control circuit.

We used to use a lot of these transformers from Simmonds Brothers, which was a proper old-school outfit – you stepped back in time when you walked in to their works.

The only time I've used that particular output range was when converting a Spanish built machine which was 3 phase 220 volt to run on 400 volt 3 phase.

You may find that the motor on your machine is already set for 3 phase 220 volt Delta, in which case ditch the transformer and fit a suitably sized VFD. You will probably have to fit a 240 – 24 volt transformer for the control circuit as well.
10 March 2016 at 21:32 #229388
Chris Richards 3
Participant
@chrisrichards3
Thanks for the info so far, I appreciate I didnt provide much to work from so I've just been attempting to trace wires so I can make a simplyfied wiring diagram.

So this is how I think its wired up:

3 phase 415v comes in to 3 fuses and splits off to the following

—>Main Cabinet Transformer splits voltages to:

—>85v 3 Red wires –> 160v Capacitor –> 3 axis servo amplifier —> Servos

—>240v 2 wires blue, brown —> Controller Top board

—>110v 2 wires —> Controller End Board

—>24v 2 wires —> Controller End Board

–>Yellow box Transformer —> power drawbar

–>Coolant Pump

–>Spindle motor switch

More Photos to clarrify:

These are the 3 fuses where the 3 phase comes in at the bottom and then goes through the switches/fuse things for the drawbar and spindle.

This is the 160v capacitor the 85v appears to go to and then on to the servo amplifier.

This is the contents of the yellow box that I previously thought went to the spindle motor but this goes to the power drawbar 3 wires and fuse go in to the this box and lots appear to go out to the switch.

This is the top board and end board 240v, 110v and 24v goes into this from the transformer. It appears this then sends power off to the monitor, computer etc..

This is the Servo amplifier board that appears to be fed from the 85v

So at this point the question is what direction to take? rotary converter, vfd to the spindle motor. Im still confusied im sure the motor is wired delta but appears fed direct from 415v. I guess the most cost effective route is always best
10 March 2016 at 23:24 #229394
Joe Page
Participant
@joepage27051
Either way your going to need three phase whether it's 220v or 415V. Motor's can usually be wired in either star (415v) or delta (220V).

If you go down the 220V three phase then you will need inverter for the spindle motor, a 24v transformer for the control, a 110V transformer for the switch gear, and an 85V transformer for the servo drive which I imagine could be quite difficult to source cheaply. Your probably talking £300-400 for the inverter, £100 for the 24v and 110V transformer and ??? for the 85V transformer. Then it depends how confident you are doing all this? You could also use a variac to get the 85V but probably talking £200 upwards.

You could get a 220 to 415V inverter and leave the insides, you would probably need at least 5hp, personally I would go 7.5hp to be safe but your talking £1500. Don't go with static or rotary converters.
11 March 2016 at 08:34 #229402
Neil Wyatt
Moderator
@neilwyatt
This may be a way of getting the 85-volt transformer:

livinginthepast-audioweb.co.uk/index.php?p=xfrmrvt227

I have only done one of these once and that was nearly forty years ago, but it worked really well.

Neil.
11 March 2016 at 08:57 #229407
Les Jones 1
Participant
@lesjones1
Hi Chris,
One thing I noticed in your post on March 10th at 21:32 was that you say
"—>85v 3 Red wires –> 160v Capacitor –> 3 axis servo amplifier —> Servos"
There should be a rectifier between the 3 red wires and the capacitor. The 3 wires could be an 85 – 0 – 85 volts single phase winding that would go via 2 diodes (This could be a bridge rectifier but only using 2 of the 4 diodes in the bridge.) They could also be 85 volt 3 phase that would go to a 3 phase bridge rectifier (Consisting of 6 diodes.) If it is 3 phase then when you power it from single phase you would need a larger capacitor. I noticed this while wondering if it would be possible to use the big 3 phase transformer by feeding it with 240 volts into the 240 volt tapping. If the transformer is an auto transformer then the winding would probably be all the same gauge wire so this should not be a problem. If it was a normal transformer then the 240 volt winding would probably not be able to carry enough current using it as a primary. I think the 85 volt supply for the servos will take the most power (Other than the three phase motors.) Do you know if the big 3 phase transformer is an auto transformer or a normal transformer ? (All secondaries isolated from the primary.) While trying to find a schematic I found this manual that may be some help.

Les.

Edited By Les Jones 1 on 11/03/2016 09:05:51
11 March 2016 at 12:34 #229444
Chris Richards 3
Participant
@chrisrichards3
I'll see if I can look again at the wiring to answer the questions. I did look on the transformer for a 240v input but it appears to just have 415v and 380v input.

What kind of issues would running it off a 5hp rotary converter cause? That's a tempting simple option but I assume the imperfect supply may cause electrical problems.

Thanks,

Chris
11 March 2016 at 12:52 #229447
Tony Ray
Participant
@tonyray65007
Airlink transformers will custom wind you a toroidal, replied to my query within a day or so

(500va 440v to 1x110v + 1x24v). £92.50 + vat + delivery suprisingly affordable given that an off-the-shelf 550Va laminated with only on secondary is £50 +

they do 42 +42 V of the shelf which is I would suggest near enough,given that the input side will fluctuate in voltage anyhow

**LINK**
11 March 2016 at 14:13 #229459
Joe Page
Participant
@joepage27051
Neil – I think these would be far too small but I certainly wish myself knew about these long ago.

Les Jones – It's definitely a 6 diode bridge, second picture shows five wires going into a rectifier. Like you say it will need a bigger capacitor or a bank of them, only problem is a bigger capacitor, the more surge current, I noticed a NTC thermistor to limit surge current so without doing any calculations I would probably just double the capacitance at most.

Tony Ray – I think this sounds a really good option, they are unbelievably cheap. With the size of the auto transformer just to power the control and servo I would assume he would be needing quite a few transformers, it looks around a 5KVA size transformer, although just speculation. I couldn't imagine the servo's needing more than 500W each though.

I was hoping the control boards would have stated their make or ratings so we would know what power we're dealing with. Chirs, would you be able to tell us the ratings of each of the servo motors?

Rotary or static converters are just about ok for running motors with pretty constant loads like compressors or conveyors. I have heard a lot of people drive lathes and millers and found their motors are noisy or run quite hot. I wouldn't want to try it on a cnc, I may be wrong, some may be doing it but I would advise against it.
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