Forgot to mention, there is a dedicated forum over on Practical Machinist which is probably worth a read - https://www.practicalmachinist.com/forum/categories/transformers-phase-converters-and-vfd.11/
- Thread starter frank horton
- Start date
Gareth J
Member
- Messages
- 3,507
- Location
- North Cornwall
Are you sure you would need such a big battery set? I'm not 100% sure if it's possible but I think you might be able to do the following;
-DC from panels, into batteries and/or
240VAC transformed to DC into batteries.
-DC from batteries inverted into 3phaseAC with a suitable inverter. If such a thing exists.
You would only need as many batteries as made sense financially. Which would probably be roughly one spring/autumn nighttime's energy use.
Edit;
I think it's doable but don't know if there is a single inverter that will do the lot. More likely you'd need a 240V single phase "hybrid" inverter that is rated at a bit above the highest continuous current draw your 3pg setup will demand. And a second, "island" 3phase inverter, running off the batteries, that's rated at just over the maximum startup current you're likely to require. Multiple inverters are likely to start stacking up the costs but they are getting surprisingly inexpensive.
You'd only need to run the 3phase stuff from the big inverter, household side would be run off the single phase hybrid. Meaning the 3phase inverter could be shut down if the workshop was closed.
I can't be bothered watching videos, so let me guess, he's only feeding two coils of the idler motor, and using the other 4 for generating?
The big flaw with only feeding certain coils, is all your 380/415V output is generated, so unless you use a grossly oversized motor, the output voltage will sag a lot under load, as standard squirrel cage motors are not good generators.
Seadog
Save the planet. It's the only one with rum!
- Messages
- 12,164
- Location
- NE London - UK
No. The system starts with 240v across two phases, with a capacitor feeding the third. Once spun up, the cap. is briefly kicked out of circuit (since it's effectively a short circuit, and would damp and slow rotation too quickly), the 240v is then switched across one phase and neutral, and the cap. switched back in with an additional one feeding the third phase. This gives you a true 3-phase, with neutral. You need a star connected motor with the neutral brought out, obviously. It's on my todo list and I've already had a play with the configuration.
Er...yes. Although I got the number of coils mixed up (I was thinking about a totally different motor!).
What you are in effect doing is generating 2 false legs, and relying on motor inertia and the capacitors for the two false legs, so you'd need a quite oversized idler motor to avoid sudden loads from stalling the idler, and to ensure the output voltage doesn't sag too much.
And also to stop the powered leg of the idler from cooking, as nearly all power entering the system will be going through that one leg, so if you want to power a 1hp motor, you'll need a 3hp idler.
It's not like a conventional RPC where additional motors are getting most of their power direct from the single phase, with only a third coming via the idler, and where additional motors help stabilise the false leg.
The big downside is you no longer get two legs that are full power, so you don't get two 'good' legs for control circuitry.
On 230V, or with a step-up transformer, you have two legs that can provide near full voltage under load, which to avoid relay/contactor chattering issues with voltage sagging under start-up load, you should aim to connect whatever controls the relays/contactors to those legs.
It's also worth mentioning that if using capacitors, you never get true 3-phase.
The capacitor capacitance and motor inductance interact to cause the phase timing to lead and lag the perfect 120deg, so you only ever get perfect timing under specific loads, plus the voltage will also vary separately.
If you get values badly out, the extra rotational vibration can be very noticeable in any running motor.
Blue Chips
Forum Supporter
- Messages
- 622
- Location
- Maine, USA
I set up a 220-240V rotary 3-phase converter about 17 or 18 years ago. I don't remember where I got the components, but as I recall, the idler control circuitry was preassembled and installed in the steel box. I seem to remember wiring up the receptacles, switch, mains cord, and idler connections. It uses a 7.5 hp Leeson/Gentec idler, with no external shaft. I wanted the converter to be portable, but have a steady base, so I modified a hand truck to accommodate it. It's still working fine and runs my mill and lathe smoothly. I wish I could give you more specific information, but it's been quite a while since I set it up. I do remember that I saved a fair amount of cash by buying separate components and doing the rest of the work myself. I might still have the instruction manual around someplace.
Just for comparison, here's a link to a spec sheet for a unit that also uses a 7.5 HP idler.
https://www.northamericaphaseconverters.com/wp-content/uploads/2019/04/SB-7.pdf
brewdexta
The biggest tool in the box
- Messages
- 5,607
- Location
- UK
I bought a 10hp digital drive, it drives my whole workshop. Here's some pics of it https://www.mig-welding.co.uk/forum/threads/lathe-swap.53699/page-26#post-647134
It runs all my 3 phase kit, I just have to be careful not to start the screw compressor and the big lathe with the 7.5hp motor at the same time. I bought the soft start option do it dampens the in rush current a bit.
Cracking bit of kit.
It runs all my 3 phase kit, I just have to be careful not to start the screw compressor and the big lathe with the 7.5hp motor at the same time. I bought the soft start option do it dampens the in rush current a bit.
Cracking bit of kit.
Burdekin
Chief Bodger
- Messages
- 6,685
- Location
- Aberdeen
I thought they were a lot more expensive. Are they still sold?
no one is going to fire up their steam boiler, wait for it to get hot enough then start running a steam powered generator every time they need to turn a 3 phase machine on?
brewdexta
The biggest tool in the box
- Messages
- 5,607
- Location
- UK
Yes, if you don't see what you want on the web site, give them a call, it's a small family business. You probably don't need 10hp if your biggest motor is 3hp.
He was running the same 7hp Colcester triumph lathe as me off of his own devices which helped make the decision.
I got a quote from Drives Direct years ago, and they were determined that I needed a grossly oversized digital converter that wouldn't give me much change from £7k.
Even with having to add an isolation transformer to my current setup, it's only cost me around £1200, however the 7.5kva isolation transformer would cost more than that now. It only cost me £425 delivered 3 years ago
Even with having to add an isolation transformer to my current setup, it's only cost me around £1200, however the 7.5kva isolation transformer would cost more than that now. It only cost me £425 delivered 3 years ago
brewdexta
The biggest tool in the box
- Messages
- 5,607
- Location
- UK
I opted for the soft start option and the 10hp version to drive the 7.5hp lathe, The lathe doesn't start up under load so unless you have something that does have a significant load and you have the right MCB, then I can't see it being an issue. My screw compressor doesn't start up under load either, I think a valve kicks in once its up to speed by the sounds of it.
So far, 7 years on, no issues, touch wood. Nice and quiet, just a small cooling fan.
So far, 7 years on, no issues, touch wood. Nice and quiet, just a small cooling fan.
I just checked the old emails.
They said that as I wanted to power a machine with a 5.5KW (~7.5hp) servo spindle, the converter would need to be at least 3x oversize, and they recommended a 24KVA output converter, at a cost of £6600. To get a sine wave filter and/or a neutral tap would be extra.
I have been tempted to see how my setup would run with the idler motor disconnected, but I'm not sure if the VFD would run with no load connected, plus I've got no equipment left with a basic motor to test shock loading.
gaz1
Member
- Messages
- 19,051
- Location
- westyorkshire
well thats up to others what they pay out
as what the op first stated €15,000.....the pole with 3 phase on it is 14m from the meter
or the below
its up to the owners what they consider there best option
sounds crazy but it would be cheaper to pay someone to be the steam boiler man
