# Is this a DC or 3phase motor



## Shotgun (May 16, 2022)

I pulled this motor off of a treadmill, expecting it to be a typical DC motor.  But, I'm thinking now that it is actually a 3phase AC.  Is there such a thing as a 3phase DC?  It is a very smooth running motor and I'm going out tomorrow hoping to bring home a Sebastian H model lathe.

Any ideas of where I might get a controller for it?  My current setup is a bit Rube Goldberg.  The Craftsman 12x36 lathe has a 3phase that I run from a VFD.  That VFD takes 220V 2phase.  The 220V is 110V that runs through an upconverter.  It is all hidden away in the cabinet, but that is still a lot of wires and plugs.  I'd like this one to be simpler.


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## bukwirm (May 16, 2022)

It says 60 Hz 3 phase, so it's a good bet that it is a three-phase AC motor.


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## markba633csi (May 16, 2022)

Yep 3 phase.  Plus it has what is probably a hall-effect sensor for tracking speed. I guess treadmills are evolving


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## SLK001 (May 16, 2022)

Just get the controller off the treadmill.  It's perfectly matched to the motor.


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## Bi11Hudson (May 16, 2022)

According to the nameplate, it is a 3 phase motor. The associated controller probably has a synthetic 3 phase output, the same as a VFD. It likely will work as a stand alone motor as long as the voltage is correct. Base speed is 1800 RPM, suitable for a machine drive. The encoder is only necessary if used with the original drive.

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## Shotgun (May 17, 2022)

Hot DANG!!  This is excellent.  I'd use the treadmill controller (I still have it), but I have no way of controlling *IT*. So I think my best option would be one of the 220V 1ph->220V 3ph VFDs that eBay has an endless supply of for around $100. Right?

Side question:  What happens if you put a 2Hp VFD on a 5Hp motor?  Does it burn up, limit the motor to 2Hp, or not able to drive it at all?  The Sebastian shipped with a 1Hp motor, so I'm not sure I'd want 5 driving it.


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## Asm109 (May 17, 2022)

The rating is 5hp SPL.  Meaning they are using Sears hp or air compressor hp.  Means its is really a 2 or 3 hp motor.


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## macardoso (May 17, 2022)

Shotgun said:


> Side question: What happens if you put a 2Hp VFD on a 5Hp motor? Does it burn up, limit the motor to 2Hp, or not able to drive it at all? The Sebastian shipped with a 1Hp motor, so I'm not sure I'd want 5 driving it.


A big motor powered by a small VFD will have the output power limited by the thermal capacity of the small VFD. Essentially that means the motor will be torque limited to the drive's max output amps. You can set these limits in the drive parameters to avoid tripping the drive, or you can run without limits and be careful about not overloading the motor.

Conversely a big drive can run a small motor given the proper nameplate data is entered.

Rule of thumb is to not exceed 2:1 or 4:1 on the ratio between motor and drive (either high or low). This is because the VFD has current transformers sized best for the full load amps of the VFD. There is a range/resolution tradeoff, so if the drive is massively oversized for the motor, poor control of the motor can result.


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## Shotgun (May 17, 2022)

I'm liking this even better.  Combining what @Asm109 and @macardoso are saying, I should be fine with one of the VFDs that will run a 220V 3ph from 110V 1ph (Example: https://www.amazon.com/Single-Outpu...96XGPCH/ref=dp_fod_2?pd_rd_i=B0896XGPCH&psc=1).  I've got a 20A 110V circuit run to the workshop, with a hesitant desire to run 220V.  The VFD on my Craftsman 12x36 runs off of 220V, but I have an upconverter for that.


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## macardoso (May 17, 2022)

IMO, just install a 240V, 30A, 4-wire circuit to your shop. It really opens a lot of possibilities since most machinery is not 120V. You won't find voltage doubling VFDs from most better quality sources.


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## mattthemuppet2 (May 17, 2022)

that is super interesting, never seen or heard of a 3ph motor on a treadmill. Looks like a nice motor too.

As for HP, easiest way to figure it out is to multiply motor voltage by full load amps, then divide by 750 (1HP = 750W). So (230 x 5.6)/ 5.6 = 1.7HP. You should be able to squeak a 110V in/ 220V out 1.5HP VFD on that.


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## Shotgun (May 17, 2022)

It is a commercial rated treadmill (or, at least it was).  It was the beefiest frame I ever saw.  I ended up putting a couple more roller on it, which I got from another treadmill, and making a cut table for my uncle.  He builds trailers, and the cut table allowed him to sit the girders on it, and move them around under his cold saw.

But now I'm wondering:  How do you ever get 5Hp out of (230 x 5.6 / 750)=1.7Hp ?


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## mattthemuppet2 (May 17, 2022)

that makes sense. Super cool though! The motor in the treadmill our neighbours gave us (now upstairs as a clothes horse ) was also really large and heavy, had to take it out to get the treadmill up there.

Most treadmill motors that I've seen have "treadmill duty" HP ratings, which I think are what the motor produces just after a user gets jammed into the front roller and just before the motor explodes into flames. Usually the real rating is about 2/3 of that. Afterall, almost all treadmills run on 110V which is typically limited to 15A, so the most your going to get out of the wall is somewhere between 1.5 and 2HP.


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## lordbeezer (May 18, 2022)

I’ve stripped several commercial or hospital rated treadmills with 3 phase motors. Much larger and heavier built than standard type treadmills. Few had large dc motors.


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## markba633csi (May 18, 2022)

So that commercial machine was designed for a 230 volt supply?


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## mattthemuppet2 (May 18, 2022)

lordbeezer said:


> I’ve stripped several commercial or hospital rated treadmills with 3 phase motors. Much larger and heavier built than standard type treadmills. Few had large dc motors.


 That's cool, learn something new every day


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## lordbeezer (May 18, 2022)

No sir the commercial ones had the 20 amp I think plug. One spade turned opposite from other. One out of hospital best I remember was 220.


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## lordbeezer (May 18, 2022)

208-230 on both I can get to. Both had 110 plug ins.


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## markba633csi (May 18, 2022)

That's an A.O. Smith motor- I read some stuff online about that exact brand used in spa pumps where the spl means "special" HP and is 
usually inflated. It has to do with the service factor being less than 1.   Even though it says "1" on the label, it may be a lie.  
Interesting, I learned something today


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## bukwirm (May 18, 2022)

SPL usually means the power rating is the maximum possible power that the motor can produce (right before it busts into flames), instead of the maximum continuous power.


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## Shotgun (May 19, 2022)

I'm guessing here:

They put a 5Hp rating on it and use winding insulation that can handle 220V. The treadmill designer sticks it in with a custom designed 110V VFD.  Being half voltage, you can expect about 1/4 of the rated power.  The designer counts on big currents to make up a little for the lower voltage during peak times, Those peak times are expected to be relatively short, 'cause how many guys of my size can really sprint on a treadmill for an expended period of time.  (The best I can do is from the workshop to the dinner table.  Then I'm done.). So call this a 1.5Hp motor, and be happy if I get that?


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## mattthemuppet2 (May 19, 2022)

I think that's reasonable. Besides, other than a big 2x72 belt grinder, most workshop tools (lathes, mills, drill presses) of regular size will work just fine with a 1.5hp motor, especially 3ph with VFD.


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## mksj (May 19, 2022)

You are limited by the plug in the wall and the circuit/breaker, so manufactures often use peak (locked rotor) SPL Hp which is just a gross over estimation of what the motors are truly rated for. Circuits/sockets are also not designed for continuous duty at the breaker sizing, there is usual a derating of 20% for continuous use. The motor amps is 5.6A@230V three phase (which would be ~18A at 120VA) which works out to ~1.5Hp when you factor in efficiency, etc. So you could run it off of a 2 Hp VFD, with no issues. You would want to run it at 230VAC, at 120VAC the Hp would be 1/2 or 0.75Hp. There are voltage doubling VFD's, they are common to 1 Hp, above that it there are far fewer and the price goes up quickly. You would need a 20-30A circuit for 120VAC depending on the Hp/kW rating.


			https://www.amazon.com/Variable-Frequency-Inverter-Converter-HUANYANG/dp/B0775F4G47/ref=pd_lpo_1?pd_rd_i=B0775F4G47&psc=1


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