3phase generator v inverters?

[Lightning bolt]

Greetings all,
I'm in the long slow process of setting up a 'new' workshop in my 'spare' time...I have gotten some 3phase machines v.cheap & free. I have no access to 3phase mains unless I win the euromillions. So can anyone advise on which route is better to run old 3phase joinery equipment? Either a 3phase generator or inverters for each machine? Any advice much appreciated.

 

[Argus]

How big is the power requirement of the machines?

If less than about 3 kw you could change the motors to single phase which many single phase supplies will support.
Otherwise, depending on the capacity, you are into a diesel-driven alternator.
Big - size-wise.
Expensive.
Noisy.
.... other issues, too.

It's worth checking your electrical regulations on private supplies in Ireland, too, if you go down the alternator route.

A variable frequency inverter device may be a solution, but again, it depends on the capacity you need and may be expensive. Not all 'old' 3 ph motors lend themselves to running on pseudo 3-phase supplies, though.

 

[Ttrees]

Hello Lightning bolt
How many machines are you talking about?
Would a planer thicknesser be in the list, I guess so...
Most of those have two motors and seems like that can lead to some tricky work.
I haven't seen a non specialist doing one up.

A rotoray phase converter sounds like it might be for you, (not a static phase converter as you loose a good bit of power)
If you wish to use VFD/inverters, then you are limited to 5hp, but I believe you can derate a motor if you get a specific VFD.
The motor needs to be delta (240v written anywhere on motor nameplate) unless you want to dig out the star point in the windings which is a delicate process and that will take some extra study.
Bear in mind that you would be swapping switches for simple ones in most cases for cheap ones, and one VFD per machine, unless you had say, two of the same tablesaws, you could hard wire both up.

Bob (Myfordman on this forum) has a great write up on all things concerning induction motors which you should read.
Thanks to him for making this
Tom

Induction motor information here https://drive.google.com/file/d/0B_GZrXNsNxTlQzd6aldlQjJtUDQ/view?usp=sharing

 

[AJB Temple]

Thanks for posting Bob's paper. I just read that. Really informative. I learnt a lot.

 

[Ttrees]

Thank Bob AJB
It's in myfordman's signature if you need to check for it again.

 

[guineafowl21]

As above, but it would help us if you could post a picture of each motor rating plate, and give details of what types of machine they’re fitted to.

There are many options for running 3ph gear, and which one you chose depends on the machine and motor being run.

 

[Myfordman]

Genny will have to be at least 50% greater VA than the biggest motor you will want to run.
Stick to 4 pole generators as they will only need the deiesel engine to run at 1500 rpm instead to 3000 lower speed will be quieter and better matched to the power output curve of a diesel and save you fuel. One of the few plus sides is that you will be able to run on red diesel rather than road diesel.

 

[Trevanion]

One of the few plus sides is that you will be able to run on red diesel rather than road diesel.

Or kerosene and a touch of engine oil if you're a right skrimping psychopath.

 

[Spectric]

If you can get away running a generator without upsetting neighbours then it could be the cheaper option and allow you to buy and use bigger industrial machinery, better build than the modern tin framed stuff from the orient. I installed three phase in my last workshop, did everything including running a duct to the edge of the pavement so all the local DNO had to do was dig a hole, feed a cable up the duct and splice in and connect, then test but still cost me around £1800 in 1994. Biggest load I had was a 15Hp motor on a compressor. Now I am into wood I really wish I still had that workshop as I have seen so many woodworking machines that I could never run but sensible prices.

 

[Jelly]

One of the few plus sides is that you will be able to run on red diesel rather than road diesel.

Looks like that won't be allowable past 2022, as per this consultation on .gov.uk

Worth bearing in mind given how a long-term an investment a gennerator would be.

After my experiences with generators (as the implication of needing to run a 100hp motor on a site where the maximum Western Power could deliver was 50kVA) I'd definitely consider a private supply as the absolute last option; it's entirely workable, but comparatively expensive and a lot of additional maintenance work.

 

[Inspector]

I am wondering if the OP actually meant a rotary phase converter rather than a stand alone generator? May never know as he hasn't seen fit to comment since posting even though they visited the site this morning.

Pete

 

[Spectric]

Hi

That issue with Red diesel has been talked about for quiet some time, years infact but the idea is very simple. Red diesel will cease to exist, no longer available to buy so everyone buys Derv and pays the duty. Then there will be a list of users who can claim back the duty and this way the government believe they can have more control and ensure they collect all the duty under the guise of reducing air pollution. But diesel is diesel and if needed has to be used and if it cost more then someone down the line will pay the extra.

 

[Jelly]

Then there will be a list of users who can claim back the duty

The consultation cuts that down to agriculture and forestry, rail and domestic heating.

So (except in Northern Ireland where electricity generation uses are exempt from all hydrocarbon oil duty) the current lower rate of duty for "use in an engine other than a road going vehicle" would no longer be available.

If implented it's a huge step-change in policy, which has the plant hire industry (amongst many others) up in arms.

 

[Lightning bolt]

I am wondering if the OP actually meant a rotary phase converter rather than a stand alone generator? May never know as he hasn't seen fit to comment since posting even though they visited the site this morning.

Pete

Sorry for upsetting you pete! Am new to web forums & still figuring out where all things are/how they work, much like my OP on my workshop endeavors.

 

[Lightning bolt]

Thanks for all the information people, i'll read that paper on lunch break. What an amazing resource. Apologies in advance for my v.basic electrical/mechanical knowledge. What I have @ the moment is a startrite tilt arbor 12" table saw. 2.2kw output. I got onto drives direct who sent me a variable frequency inverter. Just need to bring the motor in to local rewinds shop to have it rewired to delta, not 100% sure of configuration myself. I paid €350 for the saw from a local furniture college.€300ish for the vfd. Fingers x it'll do the job. I have been offered a 12" Sedgwick planer thicknesser (old type, green colour full cast iron body) & a multico morticer for free. They both look in decent nick from pics I have seen. I was against the idea of a generator due to noise, but a friend reckons there'll be noise from machines anyway so shouldn't be an issue. Also he says it'll give me true 3phase power as opposed to 'psuedo'.
Also might not work out much more expensive than a no. Of individual vfd units...

 

[DBT85]

Ooh that was an expensive vfd! Post a pic of the motor terminals and someone can help you configure for delta and save you a bit more.

Marius Hornberger just did a video where he added. A VFD to his homemade bandsaw, key upsides for that job were variable speed (for cutting metals or plastics where you want it slower) ramp up time to prevent belt slipping at the start and braking to slow the blade down. His machine on its own took 20s to run down, with the vfd and the braking resistor fitted its now 1s.

Ive been looking at a vfd and older 3phase dual voltage machinery myself but keep umming and ahhing whether I have the time and patience to revive a cheap old machine that will still run great but is covered in a decade or more of surface rust, and then thinking about replacing the fence etc.

 

[MilesH]

....Also he says it'll give me true 3phase power as opposed to 'psuedo'.

Only the output from the old static converters can really be called 'pseudo'..... The big advantage of VF inverter drives, of course, is that they give you complete control of the motor. So you have electronic braking built in, variable feed speed for the thicknesser etc.

 

[Lightning bolt]

Only the output from the old static converters can really be called 'pseudo'..... The big advantage of VF inverter drives, of course, is that they give you complete control of the motor. So you have electronic braking built in, variable feed speed for the thicknesser etc.

That sounds like some good news, thanks for it. Hopefully it'll be running by the end of the week & I can report my findings

 

[guineafowl21]

it'll give me true 3phase power as opposed to 'psuedo'

As above - VFDs give you complete control of the motor, and have NVR and overload protection built in. Also, if you ever decide to sell the machines, you can advertise them as suitable for single or three phase supplies.

Having worked on a farm without electricity where I had to fire up the dirty old genny every time I wanted to use a power tool, I would go for VFDs every time. Also consider that you may wish to run more than one machine at once, so the genny will have to be rated for that, plus the extra loading that inductive things like motors will cause.

True 3ph versus ‘pseudo’ 3ph is pretty much irrelevant - VFDs produce a sort of chopped-up version of mains, but putting this through the windings of a motor smooths this out and will make zero difference to your woodworking. In fact, the soft start/stop functions will probably be kinder to the machines.

 

[Spectric]

Hi there

Yes a genny will give true sinusoidal three phase and as much power as you decide to purchase, ie size of genny. It can run multiple machines unlike the VSD where it is a one to one. Not all VFD's produce psuedo sine output, you can buy true sinewave convertors that will be just like a true three phase supply but will cost more. Psuedo output does increase the stress on motor windings but at low power levels is not an issue.