View Full Version : Voltage Supply?

10-08-2011, 08:25 PM
If the supply voltage for say a Leblond 16" Lathe reads 460 and 3 phase on the machine's nameplate, can this be run on regular household electric supply with a 3 phase converter?

Chris S.
10-08-2011, 08:31 PM
No, you have to supply the rated voltage... Sorry!


10-08-2011, 08:33 PM
yeah I'm a dumby when it comes to electricity. so I guess I'm limited on the size of machine I can run in my garage to anything that can be run on 220?

10-08-2011, 08:41 PM
You're limited to anything 220V unless you find a cheap old (and big!) 220/460v stick welder to use as a transformer to get from 220 to 460 before the phase convertor? Otherwise a 3-phase 460v VFD can be hacked to fool it into thinking it has 460ish when powered from 220 - a simple mod' if it has 2 banks of DC bus capacitors (i.e. is oldish and largish), I've done it for my 415v Holbrook to run it from 240v using and old ABB ACS300 series VFD - it means derating it by 30% though, so I've used a 5HP rated (3.5KW) VFD for the 3HP (2.2KW) motor. A competent electronics tech' should be able to do it in 10 minutes or so :)

Dave H. (The other one)

The Artful Bodger
10-08-2011, 08:52 PM
I thought the standard answer here would be to buy a suitable VFD?

10-08-2011, 09:05 PM
Probably the cleanest solution is to pull the present motor, put in a 240V 3-phase motor, and use a VFD to get the 3-phase power. That may not be the cheapest way out, but I don't know enough to come up with any cheap home-grown solutions so it's probably what I would do. What size motor do you need? 3hp?

10-08-2011, 09:23 PM
Recent thread on Practical Machinist suggests that a 440v 3ph motor will
run fine on a 220v 3ph output VFD at 30hz with a power output ~1/2 the
rated horsepower of the motor. If you can stand the power output drop
this is one option. You would have to be able to tolerate the motor rpm
as well perhaps by belting etc. Running the Hz of the vfd up seems to drop
the power output of the motor further as well but the thread got a bit confusing
on that point. This is a 440v motor connected as 440v but driven by a 220V VFD
Ref: http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/connecting-220vac-vfd-440vac-1hp-motor-232914/
and the original starter thread: http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/connecting-220vac-vfd-440vac-1hp-motor-232914/

For a Leblond lathe of that size the motor size may make this approach moot, depending on how much cutting you are doing
with it. Most lathes use only a fraction of the motor power, but cutting a 0.25" DOC off a an 8" cylinder would not likely be
feasible with the above approach.

10-08-2011, 09:32 PM
Check to see if it is a 220/460v motor, you will have to change the overloads and fusing, although if it is possible and using a VFD you will not need the O/L's.
The wiring guage should also be checked.
Twice the current on 220v.
The control voltage is most likely 120v, it would not be hard to supply this.

Rich Carlstedt
10-08-2011, 09:49 PM
Yes you can do it. I did it for a friend 2 years ago
Find the KW rating of the motor
Lets say it is 6 KW.That makes it about 8 HP
You will need to find a surplus of about 10 KW transformer.
( needs to have a larger rating than the motor )
This transformer would be single phase 480 to 240. ( not a 3 phase trans ! )
We found one at a used equipment outlet for 100 bucks.
Wire it backwards 240 stepup to 480 and be sure to fuse for the full KW rating.
Now get a 480 volt VFD , also larger than the motor ( + 30 % )
Even though they have 3 phase input labels, they will convert a single phase input if they have the capacity ( Like 30 %).
You may have to rotate the input terminals ( like 1 & 3 instead of 1 & 2 ) in order to find the largest internal Caps and the best output.
We found a used 10 K Hitachi VFD for 150 bucks and it is superb.
The only issue is the auto break on my friens lathe sometimes interfers with "ramppdown" and he gets a fault. But , that is peanuts

PS I differ with the comment on using 220 Volt. You only get 25 % power, not 50 percent. Half voltage gives half amperage= 1/4 KVA

10-09-2011, 05:27 AM


10-09-2011, 05:58 AM
If the supply voltage for say a Leblond 16" Lathe reads 460 and 3 phase on the machine's nameplate, can this be run on regular household electric supply with a 3 phase converter?

UK phase converters like the 'Transwave' usually incorporate a boost transformer.

It's also possible to re-wire many motors for lower voltage. Star/Y to Delta link are common in the UK, but you can also often convert motors without them; http://bbs.homeshopmachinist.net/showthread.php?t=39602&highlight=motor+rewire

10-09-2011, 10:10 PM


Drives Direct is pretty proud of those. Too bad there don't seem to be
any equivalents available directly in the US. $500+ is fairly steep for
a 1 HP drive. They don't seem to have a direct order website, at least
when I prowled around on that site last year. For US types, this is the
continental equivalent of the 115vac in 230v 3ph out VFD available in
the US. Not sure a 16" Leblond has a 3hp motor, suspect at least 5hp,
even 7.5. Dunno, OP hasn't said, so likely the Drives Direct VFD would
not suit anyway and the 3 HP VFD pushes $1000.
Boost xfmr probably the cheapest route, if suitable can be found
and potentially heavy SOB though.

Paul Alciatore
10-09-2011, 10:54 PM
If you stay with the three phase, 460 Volt motor, getting the proper or improper Voltage/current/phases for the motor is only part of the problem. Chances are there is also some control circuitry and it probably runs on 230 or 115 Volts. Contactors, indicator lamps, etc. You need to look at the total wiring, not just the motor. Actually in any case, you need to look at the total situation.

J Tiers
10-10-2011, 01:36 AM
You said the *machine* plate said 460.........

Look at the MOTOR plate to be sure it is NOT a 230/460 motor, which would solve many problems directly

You would need also to check the control coil voltages, and see if there is a transformer, which also might have a tap for 230

10-12-2011, 06:59 PM
Thanks guys! This has been real helpful - I think! All this electronics talk is over my head but I guess when I get into it it may be more simple than I imagine.

10-12-2011, 07:54 PM
Yes it can be done this is probably the cheapest and easiest way to do it. House voltage is 120 and 240 single phase. You need a 2 to 1 ratio transformer to step up the voltage from 240 to 480 VAC. You can buy a transformer on ebay. You need to buy a transformer that has the same watt rating as your equipment motor. Now you need to build your own 3 phase converter that will work on 480 Volts. Buy 2 motors the same size, buy 3 phase motors at a local motor repair shop or on ebay. Used motors can be picked up for scrap metal price. You also need a single phase motor. The combined watt rating of the TWO 3 phase motors needs to be the same at your equipment motor. The single phase motor only needs to be about 1/4 to 1/2 hp. Mount all 3 motors side by side and connect all 3 motor shafts together with V belts. Wire the two 3 phase motors in parallel make sure they are wired for 480 VAC too. Connect L1, L2, L3, to your equipment. Connect L1, L2 to your 480 VAC step up transformer. Turn on the single phase motor it will get both 3 phase motors up to speed. After both 3 phase motors are up to speed turn on the 240 VAC to the transformer then turn off the single phase motor. The two 3 phase motors running in parallel act like a generator on wire L3 they generate power to each other and you get real 3 phase output on L1, L2, L3. Your equipment will run fine and your control circuit voltage will work fine too.

If your 3 phase equipment motor is a multi voltage motor you can wire it for 240 volts and you do not need the step up transformer.

10-12-2011, 10:45 PM
If I were doing this... I'd run a single 240 volt 3 phase motor as an ider (pony start or not - your choice) and feed that output to a three phase 240-480 transformer. It's a lot easier /cheaper / safter to tune (capacitor) your rpc at 240 than 480.

Oh.... 240 tingles - 480 fries... 480v rms is 679 volts peak. If it runs 5% high - make that 713 volts.

There is an entire forum over on PM devoted to RPC/vfd etc. if you are contemplating doing this yourself, read that forum carefully.

Stuart Br
10-13-2011, 03:48 AM
One vote for the technique described in post #7. I run a Colchester Chipmaster using that exact technique. I don't do any real heavy work though. I used a 2HP (1.5kW) VFD
Details are at


10-13-2011, 09:31 AM
Your situation is the same as mine. 440 3 phase lathe running on 220 single phase.

I have a rotary phase convertor going into a 440-220 transformer wired backwards.

Works great, and has for 8 years now.

Another bonus is with 440V the wiring is cheap, I have 10 gauge wire after the transformer.

My lathe is a feeler (Hardinge HLV copy) and has a huge but only 1 horse motor so my transformer doesn't have to be very large. If you have a 3 or 5 horse motor the transformer might be hard to find ???