How much of a problem is 3-phase?

[sparkysy]

I too have a inverter from drives direct for my lathe It works very well indeed, I think brewdexta said it well above they don't have great torque at low speed but on a lathe or mill with all the gears it doesn't matter too much! They are very useful bits of kit for motor control and safety! 3 phase kit is usually better as it lasts longer seems to run nicer you get smaller than the equivalent single phase motor.
Sy

 

[AdrianH]

All this talk of static converters and VFD'S has given me a brainwave, I have a 8hp 415v static converter that runs my universal woodworking machine, if I take the output direct from the transformer in the static and feed it into a suitable VFD it would give me a true balanced 3 phase supply with all the benefits of a VFD.
Looks like a suitable VFD with a 380v input would be around the £250 mark.

Yes and no! If the VFD are 3 phase then they will have a three phase rectifier to charge up a capacitor bank to around 590 Volts DC, this is then converted back to sin wave of varying frequency, if you now only feed with single phase you will be missing an input leg and place more current load on the other parts of the rectifier. So going to full load could cause some problems.

Have a read of this post on another forum.
http://www.practicalmachinist.com/v...le-phase-power-into-vfd-rated-3-phase-153478/

Adrian

 

[Burdekin]

I have a boost energy converter and looking at spurring off it to supply my workshop with 3 phase. Anyone done this? Any recommendations? Any issues to avoid? I have an electrician friend so this might be one for him.

 

[WorkshopChris]

My garage is fed with a 63A supply, currently broken out to a 5A light, 20A socket ring and a 32A socket for the welder. Can I feed a 3-phase converter thingy from one of these?

Is the 63A the rating of the incoming fuse/ breaker or the rating of the fuse/breaker it is fed from?
Depending on distance that would probably be a 25mm swa cable?
One of the biggest factors with phase converters is voltage drop on start up.
We have one at home feeding machinery the only thing it doesn't like starting is the cylindrical grinder.
Fed with a long run of 35mm and 16mm cable.

 

[Pete.]

Just put single phase motors on and be done with it. A fume extractor motor is smaller than a 3hp compressor motor. My fume extractor is badged 2.2kw on 110v but the actual motor is only 0.75Kw - the rest being used for the electrostatic precipitator.

My lathe had some tiny little 1kw ish single phase motor on it, which I ditched and went for three phase but the point is it wasn't a big motor.

Not sure about the size of my mill motor, but its not on gigantic wiring, and the first thing that happens is a reduction from motor speed to 600rpm before any drive is taken off the shafts.

Three phase motors are smoother, but realistically I'm not turning out aerospace quality components on my half century old equipment.

I did this and I'm going back to three phase. I've been buying cheap but good quality inverters in readyness.

Here's one of them http://r.ebay.com/NhxKej

One thing I have found is that the switch from 3 phase to single can sometimes be less than straightforward. Quite often it involves adapting the motor mount as sometime (like on my Denford) they use 415v coils in the contactor which won't pull-in on 240v, so you have to change or adapt those too.

 

[Kent]

Yes and no! If the VFD are 3 phase then they will have a three phase rectifier to charge up a capacitor bank to around 590 Volts DC, this is then converted back to sin wave of varying frequency, if you now only feed with single phase you will be missing an input leg and place more current load on the other parts of the rectifier. So going to full load could cause some problems.

Have a read of this post on another forum.
http://www.practicalmachinist.com/v...le-phase-power-into-vfd-rated-3-phase-153478/

Adrian

What are those turny box things you use on your machines called?

 

[Kent]

My neighbour runs all his 3 phase of a genny. Two lathes (ones a monster) welder (which they cant use too great LOL) Milling machine and a four post ramp.
If you don't have neighbours its a very economical way of doing it especially on the right fuel.
most three phase connections I hear of seem to run North of 15k, that's a lot of genny money

 

[doubleboost]

I bought a Harrison lathe that came with a "rotary converter" (Transwave)
This gives 440 3 phase from a 16 amp plug (up to 3 HP)
You can simply plug any machine in (3 phase 440 volt) and all the pumps power feeds work lamps , switch gear ect will work
I have just bought a "Progress drill" this works no problem
I went to view a Colchester student lathe fie a mate
We took my converter wired a plug on to the lathes armour cable pluged it in and were able to test the lathe
This is a well tried and tested method
It works duel speed motors properly
I can do a bit video & include it in tonights night cap if this would help

 

[Burdekin]

Thanks. I already have a converter which I plug lathe and mill off. Was thinking of spurring off and running sockets in another room for grinder and drill.

 

[Pete.]

Loads of people do that. It's convenient for plumbing in multiple machine you just have to make sure you don't run too many concurrently so you overload the converter, or the supply.

 

[Burdekin]

Thanks. Messaged my electrician friend so will see if he can put in a few sockets for me.