[CSX66]

Hi All,

Been a long time reader and only just started posting. I recently bought a second hand CNC knee mill. It's 3 phase but I only have single phase in my workshop. I'm happy with the workshop setup and thought about 3 phase power when I built it but the cost just wasn't within my budget at the time.

Years ago I rebuilt a big old old Cincinnati Tool Master vertical mill and I machined up an adapter to put a single phase motor on it along with rewiring the electrics to suit. This time I figured I could use 3 Phase for future machines (I'm keen to get a CNC plasma table) and converting the CNC Mill was an order of magnitude more difficult and would mean a lot of down time while I sorted it out. Rather than mess around I bought a Phase Changer 4KW/5.5HP Phase converter. That way I can just plug the new mill in and I'm up and running.

If the advertising blurb and claims made are to be believed it should be a good thing. They are an Aussie company and only about an hour and a half drive from me If I have any troubles with it. Home Page | Phase Change Converters

I'm currently installing it and should have some pics up soon. I''m getting it direct wired it in with a dedicated isolator switch on the wall for it along with a 10A 3 phase outlet next to it. I'm running a 6mm feed in to it as it's nearly a 40M cable run back to the switchboard. The manual says 4mm is OK but go to 6mm for longer runs (I usually prefer to over engineer things) besides the cost of 6mm cable is not much more than 4mm and the effort to install is about the same.

Looking forward to seeing how it runs.

Cheers

Mike

[CSX66]

Here'a a view inside the Phase Changer. There is a small switchboard on the side with a breakers for the incoming 240V single phase and the outgoing 415 three phase. Had to take the lid off to run the cables into the switchboard.

[handlewanker]

Yep.....way to go.....messing with single phase is for the birds.......I bought one like that almost 10 years ago, about 2 grand..... works perfectly as it senses the load and adjusts the capacitor bank and voltages on the generated phases automatically.

Previously I used a home made rotary phase converter with a 2 HP 3 phase motor and a bank of fixed capacitors that, while the system was free wheeling , had the voltages almost equal on the generated phases, but as the load fluctuated so did the voltages which led to a bit of overheating in the mill motor after an hour of running time.

When I'm done with it I could still sell the phase converter, but a 3 phase line in from the company is a pay and forget option.
Ian.

[CSX66]

Well the installation is finished and I fired it up today. Seems to run fine. Haven't hooked a load up to it yet as I've got to relocate my old mill and then move the new one in before hooking it up.

Attachment 301458

Got to tidy up the wiring for the shed Sub woofer that's hanging behind it.

They've gone up a bit in price since you bought yours Ian. Just over $4K for the unit now plus the cabling and connections on top of that. Still cheaper than getting 3 phase pulled in from the street.

Cheers

Mike

[FastFarmer]

3 phase conversion is all total BS.

We went through this with 2 X 10hp irrigation pumps that ran in parallel. Put real load on a phase convertor and they soon grind to a halt. They have NO real power in them and are inefficient. After lots of pain we installed a 25kva Mitsubishi generator and never ever looked back.

[CSX66]

Thanks for the feedback FastFarmer. I have no association with the company that supplied the converter box, Just read about them online and figured it was a solution to my problem. I hope I haven't blown my cash. They advertise it as being 95% efficient and it has a bunch of Capacitors to cope with hard starts etc.

What sort of feed were you using for the pumps? I have a friend on a farm that is on SWER that was considering one to run his Lathe after looking at the box I bought. He used to be closer to town and had dedicated 3 phase but now he's moved out to the farm he can't run any of his machines. He's also been looking at the generator option.

Cheers

Mike

[handlewanker]

3 phase conversion is all total BS.

We went through this with 2 X 10hp irrigation pumps that ran in parallel. Put real load on a phase convertor and they soon grind to a halt. They have NO real power in them and are inefficient. After lots of pain we installed a 25kva Mitsubishi generator and never ever looked back.

Huh.....are we talking about a rotary 3 phase converter or one of those solid state ones that rely on a whole load of circuitry etc to produce the 3 phases?

Although I don't load mine up all that much, sometimes I work for a couple of hours on and off powering a 1-1/2 HP 3 phase motor on my mill.....the rotary converter is very quiet and you can hardly hear it when it's working.

One thing I will say........now that I have 3 phase I'll never use single phase motors again....that is, the single phase synchronous type......some pieces of machinery have brush motors built in so they stay as is.

3 Phase motors are relatively dirt cheap as well as being very compact too......and with a VFD you get infinitely variable speed control too.
Ian.

[FastFarmer]

Well for a lathe that is max going to be 3hp and hardly going to be cutting 2mm of material at a time then maybe it will work well, but I've told you my experience - total waste of money. A generator is more versatile, can be used elsewhere, and can be setup to power your whole place when the power goes out and that bushfire is coming towards you.

At 1.5hp, of course your not going to have a problem with a rotary phase convertor and yes, 3 phase motors purr where single phases scream.

[CSX66]

Well this one is rated at 5.5hp so we'll see how it runs the 3hp motor on my mill. A buddy has a 100Amp 3 phase plasma cutter that I plan to borrow and try out so it'll be interesting to see how that goes.

Cheers

Mike

[CSX66]

If I lived on a farm I'd probably go for the 25KVA generator too. It makes sense for your application. Plus you can pick them up new for under $7K. Unfortunately for me being on a residential block I think the neighbors wouldn't be too happy about the noise of a diesel generator running. Especially since I do a lot of my work in the shed at night.

Cheers

Mike

[handlewanker]

Hi, on a residential basis, a generator has no place whatsoever.........pure noise generation will piss the neighbours off big time.

Last year our electricity company notified us that the power would be off for approx. 4 hours while they did some urgent maintenance on the sub station.

No problem, I have a 5 KVA camping generator, so I fired that up to keep the 2 deep freezers and a fridge happy for the 4 hours etc...........that was a pure test of endurance.

No way would I want to have a genny going all the time......4 hours was enough, even at 54 decibels, and that was rated as being suitable for a campsite.

If I was faced with a power outage on a regular basis I'd probably go for a battery bank, inverter and and some solar panels with a mains top up as required........you couldn't get much quieter than that.

BTW........if I was running machinery or pumps with a 20 HP rating I would definitely be having a 3 phase mains connection, or a generator if in the backwoods far away from the grid, not some underated 3 phase converter set-up
Ian.

[CSX66]

Well I've been using the Phase changer for a little while and it seems to be going OK. I had an issue initially in that every time I turned the mill spindle on the Prototrak computer would reboot. It turns out one of the idiosyncrasies of the phase changer is that under initial load The voltage on L2 drops. Checking the step down transformer in the Mill control box and it is wired between L1 and L2. The drop in voltage on L2 meant the votage output of the step down was also dropping. Enough that the computer power supply would drop out. Rewired it to L1 and L3 and all good as gold.

Cheers

Mike