three phase from 240v.....

[frank horton]

storey so far..
bought my house with the promise from the lecy board giving an approx cost to up-grade the house / barn to 440v at around €1200.......
they now want €15,000.....the pole with 3 phase on it is 14m from the meter.....!!!!!!!!

so onward .....we have decided to get a 7.5KV solar system later this year but without batteries for the mo.....
proposed day time use is from solar power, night time use from the mains using the special change over switch required....
Then within a few years to upgrade the PV to around 10KV and add the necc bateries to go totally off grid....
I've had a quote for an inverter box to get 3 phase from the solar system starting around £8,000....ouch.....but they are iffy about the size of the motors........

I have 8x3 phase machines, none with over 3HP motors.....

The question......
I hate electronics, so is it better to use/build a rotary converter or the electronic inverter type.....I want one inverter to supply the whole shop NOT 1 for each machine....
I need 3phase as some of the machines need reverse direction.....mills n lathes.....
simple is best and living in the wilds there nobody to install the inverter or fix it if it when it all goes wrong....

Normally wouldn't think of a PV system but our electric has gone from just 150euros for 2 months to almost 800 for the same useage....

our house is up a private road 1/2klm from the nearest house, so nobody is nicking electric....

be glad of some ideas please.......I have only limited knowledge of this kinda thing....Ta

 

[Burdekin]

I use a 3kw rotary converter to run my mill, lathe and drill press. The brand is Boost Energy but they are no more from what I can see. I just have it all wired in to outlets at each machine. Works fine for me and machines are plug and play.

 

[addjunkie]

Drives Direct - Digital Phase Converters - How To Choose

Drives Direct - Digital Phase Converters. Your One Stop Shop for any Power Conversion Project. Single Phase to 3 Phase Converters; Various HP Inverter Units; 240 Volts three phase output; Single and 3 phase motors; cables; plugs and sockets; Inverter Neutral Generators; Rotary Phase Converters...

www.drivesdirect.co.uk

read this…..

I think rotary convertor is simplest way, others will be along advocating 3 cheap chinese vfds. But the inverter types work well too. Not sure on reliability though.

 

[sako243]

If none of the motors are above 3HP what about swapping them out for single phase ones? They'll still be reversible.

 

[Gareth J]

A static or rotary will do the job with fewest setting and knobs.

However, in your situation, as you're planning batteries anyway, can't you input your PV (or grid electric if it's dark) into DC batteries, then generate 3phase out with a hybrid inverter?

Edit; ah, actually normal 3phase hybrid inverters will probably want to sense 3phase and have somewhere to push excess solar (the 3phase grid). They probably exist as off-grid systems but I don't know about them.

 

[Matrixx]

Use a Variable speed drive to start the motors and avoid the massive inrush currents?

 

[gaz1]

steam is cheaper

you can boil your water in summer whilst also charging your batteries with solar power

or solar pv can be used as a booster to the solar heater

 

[minimutly]

Ideal way to scalp yourself, I wonder why it went out of fashion?

 

[gaz1]

Ideal way to scalp yourself, I wonder why it went out of fashion?

it went out of fashion due to electric coming in yet where electric is hard to get its still used or other alternatives used instead

boilers and heat exchangers all for steam has now changed in leaps and bounds steam power is a good alternative if you want to power tools

even homemade solar collectors can do it

 

[m_c]

For a couple machines I would normally suggest individual VFDs, but for 8, that'll get expensive.

I personally run a VFD as a rotary converter, but to start a motor, it has to be quite a bit oversized. You'd be looking at at least 3x3HP provided none of the motors are starting under high load, in which case you'd probably need at least 5x rated motor power.

If you're planning on going off-grid, then I'd be speaking to the inverter supplier to see what is feasible.

 

[daleyd]

Can you do a vfd (or a couple) and some switchgear/plugs and sockets?

You would need to either remember to stop the vfd or have some sort of interlock to prevent switching over when it's running. Downside is you would need to swap out any 440v switchgear as it wouldn't provide power for 440v relays etc like a rotary converter.

It's obviously not going to be great for a production environment but for a home workshop where time isn't quite so important it could work.

 

[Turbo]

Running different machines off 1 vfd is not a good idea unless they all have similar motor sizes.

You set up the parameters in the vfd according to what size motor it is running. If you have it set up for a 3kw motor but run a 1.5kw motor on it & the motor gets overloaded the motor will be cooked before the vfd senses it.

 

[frank horton]

thanks for the reply's........

a big enough battery set will cost over €15,000 euro's at the mo and who knows in the future.....
as for changing all the motors, to much trouble, then theres the cost of around €300 per motor..plus the switch gear....

where can I find details of a rotary converter build, thought it was a big 3 phase motor perm running in the backround and some capacitors.....
well not quite so....but u get the idea......
anyone here built there own system....
problem here is just getting stuff.....new items have to come from Germany-Poland etc.....and often dosen't arrive......
used stuff is almost unavailable....

 

[Kayos]

it went out of fashion due to electric coming in yet where electric is hard to get its still used or other alternatives used instead

boilers and heat exchangers all for steam has now changed in leaps and bounds steam power is a good alternative if you want to power tools

even homemade solar collectors can do it

Having worked on quite a few de-steaming projects, with a few more coming up this year, it is not the technology I would be recommending

 

[daleyd]

Running different machines off 1 vfd is not a good idea unless they all have similar motor sizes.

You set up the parameters in the vfd according to what size motor it is running. If you have it set up for a 3kw motor but run a 1.5kw motor on it & the motor gets overloaded the motor will be cooked before the vfd senses it.

I know, but it’s an option and is probably ok for a home workshop (your unlikely to be running machines unattended),quite a few people on here I know have done it. You can fit overloads for each motor if you were worried, which most manufacturers recommend when running multiple motors.

 

[8ob]

storey so far..
bought my house with the promise from the lecy board giving an approx cost to up-grade the house / barn to 440v at around €1200.......
they now want €15,000.....the pole with 3 phase on it is 14m from the meter.....!!!!!!!!

At this rate its going to be worth stepping back in time and installing line shafts to run all the machines, a Lister or Petter chugging away all day would only consume a pisspot full of diesel.

 

[Burdekin]

Frank this one is the same brand as mine but up to 16kw. https://www.facebook.com/marketplac...wse_serp:b6eb0129-df29-4c7b-9bde-41fa2fc23a81

The add say it needs two 240v inputs but can use one and down rate the output. It might be too big I don't really know. Info from the ad:
Rotary 3 phase converter. Recently purchased but not big enough for my current 3 phase compressor so selling to get a bigger one. Can be seen working, collection from Hastings or if not too far could deliver at cost. It does say 2x230V but it can be used with one supply with a lesser output or split phase to run to max.

 

[Seadog]

thanks for the reply's........

a big enough battery set will cost over €15,000 euro's at the mo and who knows in the future.....
as for changing all the motors, to much trouble, then theres the cost of around €300 per motor..plus the switch gear....

where can I find details of a rotary converter build, thought it was a big 3 phase motor perm running in the backround and some capacitors.....
well not quite so....but u get the idea......
anyone here built there own system....
problem here is just getting stuff.....new items have to come from Germany-Poland etc.....and often dosen't arrive......
used stuff is almost unavailable

 

[Robotstar5]

Frank this one is the same brand as mine but up to 16kw. https://www.facebook.com/marketplace/item/1268761530358713/?hoisted=false&ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp:b6eb0129-df29-4c7b-9bde-41fa2fc23a81

The add say it needs two 240v inputs but can use one and down rate the output. It might be too big I don't really know. Info from the ad:
Rotary 3 phase converter. Recently purchased but not big enough for my current 3 phase compressor so selling to get a bigger one. Can be seen working, collection from Hastings or if not too far could deliver at cost. It does say 2x230V but it can be used with one supply with a lesser output or split phase to run to max. View attachment 380676

It would be nice to know the input current, should be on the data plate.

 

[m_c]

A basic RPC isn't a complicated thing.
Idler motor, and a couple run capacitors to support the false/generated leg/phase.
You can simply start it by spinning the idler motor shaft by hand then applying power, however you really want to add in a start capacitor with a circuit to disconnect it. This can be manual (capacitor gets connected when you press a button), or automatic.
I'd personally suggest doing it automatically by monitoring the false leg, as then it'll also reconnect if you suddenly apply a large load (this is essentially what the 'boost' light is on various commercial units).

You can get a lot more fancy than that, with automatic switching in/out of run capacitors depending on load, but provided you get a reasonably balanced voltage you shouldn't have any problems. I always aimed for the false leg voltage to be slightly high with just the idler motor running, as it'll drop under load.


There is also the issue as to whether you want to step up the voltage so you get full 380/415V 3 phase, rather than 240V 3 phase.
If you do, you'll need to find a suitable transformer.

Personally, I ditched all that, bought a Chinese 7.5kw 'boost' VFD (aka a VFD that steps up 230V to 380V) to replace the relays/capacitors/step-up transformer, and have that power the idler motor. The idler motor gives a bit load so the VFD doesn't fault out, and also helps with shock loads (such as direct starting other motors).
I also added in a sine wave filter as it primarily powers CNC stuff these days and it managed to start my old 2hp mill in top gear without any problems. For bigger motors, I'd probably go up a couple sizes, provided the incoming supply could support it.