VFD for a fairly large lathe's motor

Hello.

My brother and I recently bought a 1953 Koping S8-10 Svvedish lathe with an 11HP motor and are trying to figure out how to get it to verk. We think we likely need a VFD somewhere in the 15 Hp range. We are both fairly inexperienced and so don't want to burn down our house or fry the motor by buying the wrong vfd. We have both looked over many of the other posts on vfds but haven't seen much about a motor this size. The lathe was shown to be working before we bought it and it's really very solid for the $400 we spent; so that's good. We just need to get it chooching so we can put it to use. If anyone knows anything relevant about this kind of thing or knows a good vfd to get we would love to hear it.

Here are some pictures of the lathe:
(the second voltage on the motor's info plate was worn away (scratched off?!?) when we bought it but it probably says 240V)



We've also heard about a way to "dog leg" the 12 connections in some way so that only single phase is required but neither of us really has any idea what that meant even after some good thorough googling. If anyone knows about that... ...we sure don't. Thanks for reading to the end.

I guess you don't have 3 phase power? I suggest a rotary phase converter. I'm not sure if there is a single phase in, 3 phase out VFD in 15hp size.

If you have 3 phase, just hook it up and go.

That older motor is probably not "Inverter rated".

A VFD does not make perfectly clean A.C.,
and you rung the risk of puncturing the insulation.

digger doug said:

That older motor is probably not "Inverter rated".

A VFD does not make perfectly clean A.C.,
and you rung the risk of puncturing the insulation.

Click to expand...

Digger, what about using a choke or reactor: 3-Phase Inductors, Chokes & Reactors | E Craftsmen Shouldn't the right add-on clean up current and voltage spikes without harming function?

The inductor usually helps.

How MUCH it helps, is variable. "AN" inductor (3 phase) may or may not be as effective as 3 separate (single phase) inductors, but is better than nothing regardless. Nice lossy inductors may suppress transients somewhat better than "good" inductors with low losses.

An external inductor just takes some of the transient voltage on itself. How much it takes on depends on its inductance vs the motor inductance at the frequency of the transient. Ideally it would have sufficient inductance to cut the spike voltage that appears on the motor, but not enough to affect power frequencies much. That can be hard to do with a single part.

A more effective method is to use a purpose-made filter designed to go between the VFD and motor.

You can get 15 hp single phase input VFD‘s, but they’re going to cost about $1000.

If you have a forward/reversing clutch on the Lathe, and don’t expect to be using all the horsepower, a static converter might be your cheapest option.

A RPC for PP investment might be another option,... if you’re going to be purchasing more three-phase equipment in the future.

For small shops, which do not have three phase, with only a single three-phase machine, I generally suggest a Vfd or static depending on the situation.

If being able to very the speed, VFD is a good option.

To use a VFD as a phase converter, you will need to use a 30HP VFD if you want the full HP capacity from your motor, or if you use a 15HP VFD, you must de-rate it to about 7-1/2HP and limit the current (which will limit the speed) to about 1/2 of the VFD output rating.

Assuming you only have 240V single phase power available, buy a 15kVA transformer to step up from 240 to 480V, then buy a 480V VFD that will accept single phase input (not all of them will allow it). 480V VFDs are less expensive as a general rule.

There is no point in continuing to search for the "dog leg" way of making a 3 phase motor run on single phase unless you are adept and disassembling and rewinding the motor stator coils to insert a tap-off point inside. The guy that cam up with the concept is VERY protective of it and vehemently guards his secrets, for which you must pay to get a peek at. Years ago his info was posted here for a few months until he made the Admins take it down because it was copyrighted. So last I looked you had to pay him somewhere around $1k to look at his method, then find out after the fact that 99% of people lack the skill set and necessary winding equipment to pull it off.

Milland said:

Digger, what about using a choke or reactor: 3-Phase Inductors, Chokes & Reactors | E Craftsmen Shouldn't the right add-on clean up current and voltage spikes without harming function?

Click to expand...

Ya got's me.

I think JST answered IT pretty good, however I see no indication of amount of suppression.
As in how much spikes are above line voltage ?

Use what's called a "Sine Wave Filter" on the output of the VFD. that's what the industry calls the system that JST described; a load reactor plus a filter.

TCI, LLC - MotorGuard Sinewave Filter

DaveTheSpring said:

Hello.

My brother and I recently bought a 1953 Koping S8-10 Svvedish lathe with an 11HP motor and are trying to figure out how to get it to verk. We think we likely need a VFD somewhere in the 15 Hp range. We are both fairly inexperienced and so don't want to burn down our house or fry the motor by buying the wrong vfd. We have both looked over many of the other posts on vfds but haven't seen much about a motor this size. The lathe was shown to be working before we bought it and it's really very solid for the $400 we spent; so that's good. We just need to get it chooching so we can put it to use. If anyone knows anything relevant about this kind of thing or knows a good vfd to get we would love to hear it.

Here are some pictures of the lathe:
(the second voltage on the motor's info plate was worn away (scratched off?!?) when we bought it but it probably says 240V)
View attachment 209653
View attachment 209654

We've also heard about a way to "dog leg" the 12 connections in some way so that only single phase is required but neither of us really has any idea what that meant even after some good thorough googling. If anyone knows about that... ...we sure don't. Thanks for reading to the end.

Click to expand...

Look for Steelman-Haas conversion, 10EE MG drive motors to single-phase. PITA to do, even if one knows how.

See Jraef's comments on VFD sizing, de-rating, cost, possibility of "some" savings if boosted to 480 VAC. See also the sad-but-true need to protect a motor that old by adding a load-side sine-wave reactor.

Now.. see Wes's post (ewlsey) simple, direct, and.. ta da.. MOST APPROPRIATE to this specific need.. and go find or make a ROTARY Phase converter.

It can power the load-motor to about 90% of nameplate rating. It will not need ANY change to the controls on the Machine Tool. It will not generate ugly or damaging waveforms, load side. It WILL generate harmonic distortion, SUPPLY side, so ...if you have fussy neighbours, same transformer, then the other option is a Phase Perfect.

A "static" Phase Converter isn't. A converter.

Falls in the same category as dropping an anvil on yer toes to make you ferget your back hurts too much to hop about on one foot, and has similar real-world power delivery.

The good news is.. most Static "converters" have all the needful components, and even a maker's schematic to show you how to add an idler motor.. at which point it has become a ROTARY Phase Converter, and can actually do useful work...

2CW - And "disclosure". I have "all of the above". 2 each 10 HP Phase Perfect, one each 10 HP RPC, one each static, ripped off the back of a 7.5 HP Cazeneuve lathe it was being less than honest with, even abusing, and a coupla VFD's, not longer in use, either. Nor planned to be.

ALL my motors are OLD. Fortunately, many are also Dee Cee, so...

Before you get too far along, I would check that motor terminal box. That scratched off voltage on the nameplate, is an indication that the motor re-winder it was last at, converted it from a 12 lead to a 3 lead, and now you have a 460V only motor. Bringing out all 12 leads is a pain, and a lot of shops avoid it, to reduce costs, unless specified by the customer.

The shop where you witnessed it run, were they running it on 460V?

If it has been rewound, the upside is, it may have newer type magnet wire that is suitable for use with an inverter.

If you still have 12 leads and are interested in reading up on the Stillman/HAS method of conversion have a look here.

http://bbs.homeshopmachinist.net/threads/61256-Converting-Monarch-10ee-motor-generator-3-phase-to-single-phase?

http://www.practicalmachinist.com/vb/monarch-lathes/single-phase-power-motor-generator-10ees-153348/

SAF Ω

If you've not got a VFD yet... I believe I have one that'll handle what your looking for...new, in the box, instructions and all. Message me if interested.

just go with a RPC of sufficient size and be done with it, or if you want
to spend real money a pp solidstate.

ewlsey said:

I guess you don't have 3 phase power? I suggest a rotary phase converter. I'm not sure if there is a single phase in, 3 phase out VFD in 15hp size.

If you have 3 phase, just hook it up and go.

Click to expand...

No, you do get 15hp in a single phase 220V in. But I think his motor wants 440V.