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# Doozy alert- powering a toolroom Schaublin 102 on 110V power

#### microns

##### Plastic
Hi All,

This is going to be one hell of a long-winded and confusing post, but I could really use any help or advice with my current dilemma: how to power a Schaublin 102 bench mounted toolroom lathe using 110V single phase power. Here is the background: I live in a rental, pre-war apartment in NYC which only has access to 110V, 60Hz single phase power, from a standard residential breaker box with 20A circuit breakers (and what I am assuming is 12 gauge wire in the walls). I am looking at purchasing either a Habegger or Schaublin 102; the seller has a couple bench mounted models available but all have 220V, 60Hz, two speed motors, all around 1.5HP. Rotary phase converters, and installing 220V power are out of the question, along with upgrading the wiring in my walls. So far, I have looked into using a 1.5HP 110V 1-p input to 220V 3-p output VFD, like this: Weg - CFW300A06P0S1NB20, Invertek - ODE-3-210058-104B. I have also considered using a step-up transformer and a 220V 1-p to 220V 3-p VFD. Another option is to replace the motor entirely. The motors that the seller has are all old, noisy original Swiss units, and I wouldn't mind changing them out (buying the lathe without the motor) for a brand new 220V three phase 1.5HP unit. However, it seems that whether I get an original 1.5HP motor, or get a new 1.5HP motor, I would still be running into the current limitations of my circuit breaker and wiring. A rep from Dealers Electric gave me the following math, with the assumption that a 1.5HP 3 phase motor draws around 6 amps.

"3 phase Current @ 230V * 2 = 3 phase current @ 115V
3 phase current @ 115V * SQRT 3 = 1 phase current @ 115V
6 A * 2 * 1.73 = 20.76A Plus the conversion is not 100% efficient so the maximum amperage could be higher."​

He basically suggested that I would be limited to a 1HP motor and 1HP VFD, which I am not even sure would be suitable for the 102, since I would get even less power with the motor running at lower speeds. I don't intend to be making any huge cuts into steel with the lathe, but I am hesitant to downgrade the motor by 33% from its original spec. I am relatively new to machining, and I am no means an electrical whiz either, so any advice would be greatly appreciated. I suppose my questions/concerns boil down to the following:

1. Can I drive a 1.5HP, 220V 3 phase motor with a 1.5HP, 110V input VFD in the first place, whether it is an original swiss motor, or a modern one, using 20 amp rated circuit breakers and wire.
2. If I can do (1), should I get a new motor (probably quieter), or stick to the original, for some reason.
3. If I can't do (1), how "bad" of an idea would it be to power the 102 with 1HP 3 phase engine, and 1HP VFD.
4. Is there something easier/obvious/better that I am missing? Perhaps 110V or 220V single phase engines, or 110V 3 phase engines, or DC motors, etc etc.

Thanks to all in advance, and I hope this post made sense. And obviously I know I am dumb for living in NYC with no access to 220V power, which the rest of America (and the rest of NYC, probably) has.

Last edited:
Hi All,

This is going to be one hell of a long-winded and confusing post, but I could really use any help or advice with my current dilemma: how to power a Schaublin 102 bench mounted toolroom lathe using 110V single phase power. Here is the background: I live in a rental, pre-war apartment in NYC which only has access to 110V, 60Hz single phase power, from a standard residential breaker box with 20A circuit breakers (and what I am assuming is 12 gauge wire in the walls). I am looking at purchasing either a Habegger or Schaublin 102; the seller has a couple bench mounted models available but all have 220V, 60Hz, two speed motors, all around 1.5HP. Rotary phase converters, and installing 220V power are out of the question, along with upgrading the wiring in my walls. So far, I have looked into using a 1.5HP 110V 1-p input to 220V 3-p output VFD, like this: Weg - CFW300A06P0S1NB20, Invertek - ODE-3-210058-104B. I have also considered using a step-up transformer and a 220V 1-p to 220V 3-p VFD. Another option is to replace the motor entirely. The motors that the seller has are all old, noisy original Swiss units, and I wouldn't mind changing them out (buying the lathe without the motor) for a brand new 220V three phase 1.5HP unit. However, it seems that whether I get an original 1.5HP motor, or get a new 1.5HP motor, I would still be running into the current limitations of my circuit breaker and wiring. A rep from Dealers Electric gave me the following math, with the assumption that a 1.5HP 3 phase motor draws around 6 amps.

"3 phase Current @ 230V * 2 = 3 phase current @ 115V
3 phase current @ 115V * SQRT 3 = 1 phase current @ 115V
6 A * 2 * 1.73 = 20.76A Plus the conversion is not 100% efficient so the maximum amperage could be higher."​

He basically suggested that I would be limited to a 1HP motor and 1HP VFD, which I am not even sure would be suitable for the 102, since I would get even less power with the motor running at lower speeds. I don't intend to be making any huge cuts into steel with the lathe, but I am hesitant to downgrade the motor by 33% from its original spec. I am relatively new to machining, and I am no means an electrical whiz either, so any advice would be greatly appreciated. I suppose my questions/concerns boil down to the following:

1. Can I drive a 1.5HP, 220V 3 phase motor with a 1.5HP, 110V input VFD in the first place, whether it is an original swiss motor, or a modern one, using 20 amp rated circuit breakers and wire.
2. If I can do (1), should I get a new motor (probably quieter), or stick to the original, for some reason.
3. If I can't do (1), how "bad" of an idea would it be to power the 102 with 1HP 3 phase engine, and 1HP VFD.
4. Is there something easier/obvious/better that I am missing? Perhaps 110V or 220V single phase engines, or 110V 3 phase engines, or DC motors, etc etc.

Thanks to all in advance, and I hope this post made sense. And obviously I know I am dumb for living in NYC with no access to 220V power, which the rest of America (and the rest of NYC, probably) has.
Using the VFD will help you a lot. A regular across-the-line motor connection will draw significant current from the line even when the motor is just idling at no load. But the VFD will draw current from the line that is proportional to the actual HP load on the motor, not the motor's nameplate rating. Get a VFD that is at least as big as the motor, a little bigger is nice but but don't undersize it. Then get a cheap power meter (like a Kill-A-Watt P3, typically around \$30), plug it into the wall, plug the VFD into the meter, and start making chips. I think you'll find that you rarely ever get the current over 15A. If you do, just back off. Reduce feed or DOC until the power draw is manageable. If the power goes too high during startup, use the VFD's ramp function to accelerate over 3 or 5 or 10 seconds as needed to manage the inertia load.

Here is a numerical example of the magic of VFDs: The formula for HP in imperial units is HP = torque (ft*lb) times speed (RPM) divided by 5252. Suppose your original motor is 1.5HP at 1750 RPM. Working that formula you find that the motor rated torque is 1.5HP * 5252 / 1750 RPM = 4.5 ft-lbs. If your incoming power limits you to 1 HP, then you can only get 1.0HP * 5252 / 1750 RPM = 3.0 ft-lbs out of the motor at full speed. But when you turn down the speed, for example to 1200 RPM, you can get back the lost torque. 1.0HP * 5252 / 1200 RPM = 4.37 ft-lbs. At 1000 RPM or less you'll be able to use the full 4.5 ft-lbs that the motor can produce and still not exceed 1HP of power draw from the line.

If you have room to mount a bigger motor and \$\$ for the motor and a matching VFD you can do even better. For example, if you have a 3HP motor and a 3HP VFD, the motor's rated torque is 3HP * 5252 / 1750 = 9 ft-lbs. The VFD+ motor combo can deliver that 9 ft-lbs at any speed below nominal. If you are limited to 1HP from the line, you can only get 3 ft-lbs at 1750 RPM, as above. But at 1200 RPM you get 4.37 ft lbs, at 900 RPM you can get 6 ft-lbs, and at 600 RPM you can get the full 9 ft-lbs.

Stop overthinking. Get a cheap power meter and cut some metal. If the meter goes too high (over 15 amps or so), back off on your cuts. Sure, you might have to take a few more roughing cuts than your buddy who is plugged into 240V three-phase, but how much of your typical job is roughing? Once you get to the finish cuts your power limitations don't mean a thing. I bet you'll be pleasantly surprised how much metal you can remove before you hit 15A.

Sources for the power meter:

a domestic lathe story......I cant stand the noise that lathe makes ......OK,buy bigger house ,lathe in basement.....I can still hear the noise .......OK ,lathe in shed in backyard 20 yds from the house ........I know youre using that lathe ,cause the lights are flickering!

I also suspect that if you manage your cuts and soft start that you will be able to stay within your power constraints. If not, I know one guy who pulled from two 120 circuits with opposite phase and made himself a 240 source that way.
I don’t know if that’s at all acceptable from a code perspective in your jurisdiction, that’s on you to determine.
If I were to do that I would probably run it through a lower rated 2 pole breaker or preferably some sort of relay system so that if the breaker on one phase drops that the other phase will be automatically cut as well.
Is this circuit dedicated to your unit, or do you also need to worry about loads from your noise tolerant neighbors?
No electric drier or electric stove in your unit?

One of the secrets may be to fit a clutch to the lathe ,so that frequent motor starts arent needed...........Ive been meaning to fit a car aircond compressor clutch to a small lathe ...but never got around to it........and I dont know if it will work.

A good VFD is the power meter. You can set a maximum current out to the motor to match whatever you think you can get from the wall so it never overloads the circuit. You should also be able to have the VFD display current to the motor or output an analog signal that you can put on a panel meter or similar so that you can watch the load as you cut. Hitachi VFD will do everything you need for around \$200. Probably others, but Hitachi is what I know.

A good VFD is the power meter. You can set a maximum current out to the motor to match whatever you think you can get from the wall so it never overloads the circuit. You should also be able to have the VFD display current to the motor or output an analog signal that you can put on a panel meter or similar so that you can watch the load as you cut. Hitachi VFD will do everything you need for around \$200. Probably others, but Hitachi is what I know.
Current to the motor and current from the line are two very different things with a VFD. Most VFDs can limit the current out to the motor but few if any have the option to limit motor power which is what drives the draw from the line. There may be exceptions, but I haven't seen any. (History: I worked at Rockwell Automation for 20 years designing VFDs.)

Current to the motor and current from the line are two very different things with a VFD. Most VFDs can limit the current out to the motor but few if any have the option to limit motor power which is what drives the draw from the line. There may be exceptions, but I haven't seen any. (History: I worked at Rockwell Automation for 20 years designing VFDs.)
Is it a safe assumption that while not equal there will be a consistent correlation between the two in this application?

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