Rotary Phase Converter

[knighty]

I think you'll be fine on your 100amp supply... plasma/compressor/mig etc. will take a lot less power 99.9% of the time (maybe lots on start up)

I'd try it and see if I were you, nothing to lose, worst that can happen is you pop your 100amp main fuse... they come out and replace those pretty quickly anyway ;-)

 

[maz0]

I plan to run my 100 amp home supply 100 meters across a field to my shed/barn. Will be a beefy cable, probably 35mm for the voltage drop. Doubt you will max it out on your own using one tool at a time. These things have a habit of looking worrisome on paper but tend to work just dandy in reality.

 

[addjunkie]

I plan to run my 100 amp home supply 100 meters across a field to my shed/barn. Will be a beefy cable, probably 35mm for the voltage drop. Doubt you will max it out on your own using one tool at a time. These things have a habit of looking worrisome on paper but tend to work just dandy in reality.

I have to agree, as a one man home user, there isnt much you cant manage at home you certainly cant weld and turn at the same time. With your barn being so far, security may also be an issue.

 

[bwservices]

you can fit a non priority unit which would stop certain equipment cutting in if something else is running

like the compressor cant kick in while the lathe or rpc is starting up,so the motor surge current is kept within limits

it mightn't be needed but its an option

 

[WorkshopChris]

Just catching up on posts, will you be pushing the machine hard at its full capacity, or will little be running lighter loads? This will have a impact on what your final decision regarding converter of vfd is, from what I have read about I think I would be looking for a vfd if it's going to be working to capacity or a home built converter if it's running at lighter loads. Can the motor easily be taken off mechanical load via its clutch for easy starting.

 

[armalites]

These things have a habit of looking worrisome on paper but tend to work just dandy in reality.

Years a go a friend of mine had 3ph in stalled in his workshop for his MOT ramp. The transformer was already on a pole a few feet from the building. The power people wanted to change the transformer wiring etc due to the load. My friend went and had a chat with them and pointed out that on a Sunday lunch time with all the local ovens running the load would far in excess of what his ramp would be drawing and his would be spread across the three phases, this was when cookers ran 40a + supplies. In the end they agreed and 3ph was installed for a couple of hundred quid.

 

[timgunn1962]

Why is it that every time you settle on a plan of action, sod rears its head up. I have just got the quote from western power to put an additional 100amp single phase supply in. I was expecting £2K - turns out £7K+ will be nearer the mark. I am beginning to think plan "C" might be called for. Does any one know what size generator will be needed to start a 5.5KW lathe motor? I was thinking 20KVA but my 3 phase knowledge is a bit sketchy at best.

Generator sizing for motor starting is not quite that simple. There are variables at the motor end which can dramatically affect the starting current: Direct-On-Line start might pull 6-7 times Full Load Current, Star-Delta might pull 2-3 times FLC, A VFD with a ramp-op might only draw FLC.

At the generator end, there are ways to provide "improved excitation", which keeps the Voltage up as the generator slows down (a bit). Back in the late 1980s, we had some plant with a 7.5 kW DOL-start motor. It would start and run on a 22 kVA genset with improved excitation (Permanent Magnet Group and Automatic Voltage Regulator back then) and would not start on a 60 kVA genset without.

 

[printcom]

After much thought I have decided to go down the RPC route and have ordered a Transwave 10hp unit. But as usual its not as simple as that. I now need to beef the supply to the RPC up as its only 32amp and I think I may need to beef up the 3 phase circuit to the Lathe as its only 1.5mm. Can anyone tell me what size cable I need to supply a 5.5kw motor?

 

[addjunkie]

https://myelectrical.com/tools/cable-sizing-calculator

 

[bwservices]

you need to overspec cables around an rpc as they are more sensitive to voltage drop.
just go up a size

 

[Mr-Mike]

Sorry, not fluent in english being from the US. I run 8 AWG from the panel to the RPC, 10 AWG to machine. 3 phase motor amperage draw is surprisingly low at full load. In your case I would guess under 30Amps. If you have a long run, go a grade thicker. Suggest the flexible chemical resistant to the lathe.

 

[addjunkie]

Its the start current you need to allow for, thats when itll draw the most amps

 

[bwservices]

you don't really account for start current, as cables will only briefly experience it and can take an short overcurrent

 

[printcom]

Thanks chaps, I have been reliably informed that I only need 1mm for a 5.5kw motor. So the 1.5mm already there is sufficient. Nice when a plan works.

 

[WorkshopChris]

Personally 1mm on 5.5kw is undersized for a phase converter, as for your incoming supply go as big as you can physically fit and afford.
My incoming supply is 25mm double insulated running to a 35mm swa out to the workshop, with a 10mm run to the converter to minimize any volt drop.

 

[printcom]

The chap I got this lathe from cut the main cable quite short so I am replacing it in readiness for the RPC next week. As I have said before my 3 phase knowledge is sketchy at best.
I am wondering where the neutral wire goes, if any.

 

[daleyd]

The chap I got this lathe from cut the main cable quite short so I am replacing it in readiness for the RPC next week. As I have said before my 3 phase knowledge is sketchy at best.
I am wondering where the neutral wire goes, if any.View attachment 171206

If that’s the incoming isolator on the bottom right of the pic then it looks like it’s never had one.

 

[indy4x]

Personally 1mm on 5.5kw is undersized for a phase converter, as for your incoming supply go as big as you can physically fit and afford.
My incoming supply is 25mm double insulated running to a 35mm swa out to the workshop, with a 10mm run to the converter to minimize any volt drop.

I think the OP was referring to the cable FROM the RPC to the lathe not the single phase cable to the RPC

 

[printcom]

If that’s the incoming isolator on the bottom right of the pic then it looks like it’s never had one.

That my take as well. I was just wondering if that is correct or has someone made "modifications" over the years

 

[printcom]

I have just found a wiring diagram, I am wondering if PEN means what I think it does - Protected earth, neutral ?