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Nightmare: VFD in NYC - Powering a Schaublin 102 on 110V residential power

microns

Plastic
Joined
Nov 18, 2022
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 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.

[Mods- I am new to PM and didn't know how to crosspost in both the Schaublin sub forum and here, so I apologize if this is the wrong way to go about this]
 
[Mods- I am new to PM and didn't know how to crosspost in both the Schaublin sub forum and here, so I apologize if this is the wrong way to go about this]
Don't "Cross Post", you just cornfuse people.....:crazy:

This sub forum is the proper place for it, no where else.
 
Thanks Doug, now I know :)

Any thoughts about my VFD dilemma :confused:
Well, I can drive to NYC in under one day, but choose not to.....:ack2:
You could move to where the power is "better"....:D
Seriously, someone will come along shortly
to answer your question
 
Yes, you can "drive" that motor from 120V/20A. No, you cannot drive it at full power without going over the 20A.

Just the 1.5HP motor, if rated 115V, would draw 20A. When using a VFD, you have to account for the low power factor going into the VFD, which will not be improved by the (probable) voltage doubler setup in it to get to 230V.

If you do not run it at full power, it should work. Just remember that if you do hot full power, it will probably pop the breaker.

The use of a smaller motor and VFD would also work. No issues there, but obviously a lower max power draw. Odds are you would not notice, actually, unless you are doing something unusual. Needing high power on smaller lathes is not as common.

The 1 HP VFD will likely drive the 1.5 HP motor, for that matter, but you would want to check current draw to make sure it has some margin. And if you go over, the VFD may either shut down, or go into current limit (depending on how parameters are set, and if it has a current limit mode).
 
I don't know what your actual motor amps and details are, but I looked at a good industrial Siemens 1 1/2 hp motor at 1800 rpm and it was 4.2 amps @ 230 volts. Slower speed motors will draw more amps.

This WEG drive is good for 4.2 amps output and will work on your 20 amp breaker, but just barely. Input amps is rated at 17.7 with an output of 4.2 amps. But residential circuit breakers can only be run at 80% of rated (16 amps) continuously.

Personally I think this would work just fine for you, even if you just limited the output to 4.2 amps and the motor is rated for more.

 
My concern would be the age of the wiring in the building, the distance from the breaker and the assumption that the wire is 12AWG wire, so could present a fire hazard. Most likely the soket is rated at 15A. Typically code is that the breaker size of the VFD needs to be at least 125% of the VFD input current, regardless of what it is driving (i.e. output current is not relevant). Data sheet for the CFW300A06P0S1NB20 specifies the single phase input current is 26.5A at 110-127V, and assumes a 150% overload (HD mode). As mentioned house wiring/breaker assume a maximum of 80% working current for a circuit/breaker. So technically you this puts you at a breaker size of 35A @120V. That being said, assuming you motor draw is less than the VFD rated output and you dial down the overload to 100%, this would put you on the input side at around 18A on 120V, but could cause issues with the wiring and heating, so there is a liability issue. I will say that just operating a portable oven/air fryer which run around 1500-1800 W and cycle on/off can trip a breaker as well as the cord can get quite warm.
 
Don't change the motor for a smaller one. Just hook up the VFD and use it. The VFD addresses a number of problems.

Running a motor directly from the line means you'll draw something like 30% of the full load nameplate current even with no load. This is referred to as magnetizing current and has a very low power factor. Running the motor directly from the line also results in a startup surge of something like 5-10 times the full load current. The VFD eliminates both of those issues.

The input current to the VFD depends only on the POWER being delivered to the load and the VFD's input power factor. 115V times 20A is 2300 watts. One HP is 746 watts, so 2300 watts in theory could deliver 3HP. You'll never get there though because of losses and power factor. But you should be able to get 1HP, and maybe more. But again, that is based on ACTUAL load on the motor, not the size of the motor. If you are taking a 3/4HP cut, you will draw 3/4HP from the line, regardless of how small or large the motor is.

I'd get a cheap clamp-on ammeter (they are available for $30-50) and measure the actual input current during a cut. You might have to avoid very heavy roughing cuts but you can probably do almost anything you want and still stay under the limit. You can draw 20A for short periods (a few minutes). If you are going to run continuously then you should try to stay under 16A. But I don't see a lathe running heavy cuts continuously.

Edit: since you are using an ordinary plug and receptacle a Kill-a-Watt meter is even more convenient. Around $30.
 
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I'll only add- consider wiring directly from the panel.
it should be possible to go direct and have a "temporary" pigtail come out of the front,
something like a 12/3 stranded and keep it short, like 12' if you can. that will eliminate the possibility
of a poorly connected 14ga wire overheating in the wall. this is more important as the age of the building
goes up. if your electric is pre 1980 or so, id say this is essential.
be safe and happy machining in NYC!
 
One thing not yet discussed is that you should hard wire the two-speed motor into the higher speed, and connect the VFD directly to the motor, bypassing an motor controls. The VFD will handle those functions.
 
My concern would be the age of the wiring in the building, the distance from the breaker and the assumption that the wire is 12AWG wire, so could present a fire hazard. Most likely the soket is rated at 15A. ..................
Mention was made IIRC of 20A sockets.

BUT, it is common for the landlord or his know-nothing worker, to install a 20A socket on 15A wiring. Then someone gets a surprise. It is also not unknown for the same sort to install a 20A breaker on a circuit using 14ga wire (15A rated).

Both actions are contrary to code, as they imply a capability that is not present, and could cause a problem, especially with old-time rubber and cloth type insulation, which I would expect on a pre-war installation.

Might be advisable to check out the breaker and outlet to be sure they match as far as rating. If they do, that is claiming to be a 20A circuit. If it is 14ga, that's not "on you", since you can only go by what you see.

The 80% rule is for loads considered "continuous". A lathe almost certainly does not fit the description in most shops.

"Continuous Load. A load where the maximum current is
expected to continue for 3 hours or more."
 
Mention was made IIRC of 20A sockets.

I did not see mention of this, only a 20A breaker. Although the 80% wire rating is continuous as mentioned, and highly unlikely to occur, but with the default VFD settings and a 1.5Hp it would far exceed the rated wiring capacity if turning deep cutting and/or repetitive cutting over minutes, which could cause significant heating. Given the age of the wiring, corrosion as well as insulation deterioration, it would not be advised. Where the breaker panel is and running a separate wiring would be ill advised in a rental unit.

Specifications for the 102 motors varies by model and I assume the ones I see listed are for the 50Hz versions, but in most cases you are running at 1 Hp or less in particular on the low speed setting of a 2 speed motor. So there should be no problem with running the lathe off a 1 Hp motor. You can pick up a 1 Hp inverter type motor for a very reasonable price, I would replace the stock motor with a 1 Hp 1750 RPM motor, you can easily spin these to 2X their base speed if you need the higher RPM. You could go with the WEG 1.5 kW VFD and dial down the output to match the 1 Hp motor, if at some time you move or decide to sell it you still have the original motor. The VFD should be directly wired to motor anyway and that would also be used for speed control (not the current switch), it is also possible to fuse or use a breaker on the input power to the VFD. One last consideration, assuming the stock 2 speed motor is not a constant Hp, and the low speed amperage is less, you could use a VFD on only the low speed motor setting (VFD motor parameters/amperage set accordingly) and run the motor to 2X its base speed on this setting. Motors above their base speed usually will be in constant Hp up to 1.5-2X and then decline, torque falls off but this is compensated by the mechanical drive ratio.
Schaublin 90 & 102 Plain Bearing Lathes
102-96 with a 1-speed 1-h.p. 1500 r.p.m. motor
102-96-100 2-speed, 0.5/0.7-h.p. 750/1500 r.p.m. motor
102-96-150 2-speed 0.7/1-h.p. 750/1500 r.p.m. motor
102-96-200 2-speed 0.5/1.25-h.p. 750/3000 r.p.m. motor
 
Sure that box is not fed with 240? Although there may not be any 240 volt outlets, I would pull the cover and test across two adjacent breakers
I mean it has breakers it is post 1955 or something
Otherwise I echo the above. I would not trust trying to pull that much current from 120.
 
Most of the older NYC apartments are cloth 14g wire at best, that's why its a pain to even try running AC units in the summer. I've lived in apartments that only had 2 outlets for the whole place.

Consider renting a small artist space in Brooklyn and have a small dedicated shop vs trying to run it in your apartment. Getting metal chips on your floor and stepping on them barefoot gets old real quick.

One last thing, watch out for the fuse boxes near the outlets that have a penny wedged in there, someone at some point got tired of replacing fuses.

If you are set on running your lathe in your apartment, 115v motors and swap it out. Its not great but you will make chips
 
It would be unusual to supply the panel with only 120 volts, even if there are no 240 volt appliances. You may be able to put a 240 volt breaker in the panel and solve the problem. Opening the panel will answer that question.

A lot of 9 inch South Bend lathes have 1/2 horsepower motors. You may get by with much less horsepower than 1.5, and you could upgrade the motor in the future if you move somewhere that does not have antiquated electric. That's not a criticism, I understand the challenges of New York City. I guess a pole barn is also out of the question.
 
Many apartments and commercial buildings are wired from the transformer 208/120 wye so you might see that rather than 240. Is there a washer/dryer hookup? If so, there's probably a 220 (208?) receptacle. It would most likely be on a 30A double breaker.
 
It would be unusual to supply the panel with only 120 volts, even if there are no 240 volt appliances. You may be able to put a 240 volt breaker in the panel and solve the problem. Opening the panel will answer that question.

A lot of 9 inch South Bend lathes have 1/2 horsepower motors. You may get by with much less horsepower than 1.5, and you could upgrade the motor in the future if you move somewhere that does not have antiquated electric. That's not a criticism, I understand the challenges of New York City. I guess a pole barn is also out of the question.
You are correct, but anyone that has lived in NYC can attest to how unusual the wiring can be here. I know people that never paid electric bills their whole time in their apartments or others who suddenly get hit with bills that are a few grand out of no where because someone decided to hook up to their panel.

In NYC... don't assume, verify.
 
"...standard residential breaker box with 20A circuit breakers..."

Do you have physical access to this panelboard (aka, 'breaker box')?
 








 
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