Simple 3 phase conversion

[rons]

Does not get simpler than this. (mwdropbox is apparently NLA)

Or reliable. Just one part.

 

[johansen]

The auto transformer method of driving a single, 3 phase motor is equally simple, and delivers much better quality 3phase currents in the driven motor, than capacitor alone and hoping for 60% nominal torque.

You find a 120:240v transformer and set it up as an auto transformer to deliver 360vac, then connect a capacitor of reasonable size from that 360v source and connect it to the third leg of the motor.

The spindle motor will be enough of a rotary phase converter to run a 1/8 or even a 1/4 hp feed or coolant pump in addition.

 

[DaveKamp]

I have a Moore Jig Bore #1 1/2 in my garage. The shop I use to work at closed their doors and gave me the machine with a Sony DRO. I would like to use the simplest form of conversion possible (digital phase converter)? Too much BS to deal with on a VFD. I just want to simply take single phase 220 and convert it to 3 phase.

Have 3 phase installed in your home, have electricians replace your utility panel and pull a 3-phase receptacle to the machine. Nothing easier, and less complicated, than writing several checks.

Anything more will require a bit more dedication to the cause, and it doesn't matter wether it's a VFD, a rotary converter, or a static converter. If 'too much BS' is your hard limit, you've already exceeded it by getting the Moore into the garage.

 

[JST]

The problem is that many, maybe most, utilities will not bring 3 phase to a single residence (they will bring it to an apartment building, but it has to be used to deliver single phase to the units). Yes I know you were not being serious.

I took the "too much BS" to be the complete redo of the original machine controls to use a VFD. An RPC, or a "static converter", does not force that (nor does a PP)

 

[jim rozen]

Con Ed will install three phase service, but at that point you are on the hook for a) peak demand billing, and b) charges for VARs, not just Watts.

 

[JST]

Eh... Ameren (used to be Union Electric) does not. I have one of their (now obsolete) handbooks.

The also will not install corner grounded service.

 

[SFW62]

Thank you to all that replied! I’m sorry for not returning any replies / thank you’s thus far. Get ideas for sure. I ended up using a 7.5hp VFD (it was given to me without instructions). I got the borer to work, however I did leave something out of the equation when I posted the initial question. When the machine was at the shop the 3 phase 220v came from the outlet to a power disconnect on the machine, from there it went to a 220-440 transformer then basically to the machine. So, when I hooked up the VFD ahead of the transformer, the transformer buzzed like one powering a large building. I used the machine back at the shop many times and it was always quiet. I’ve somewhat read up on this situation and it sounds like it’s not the best idea. I’m still trying to figure this situation with the buzzing out. Thanks again for all the input,
much appreciated.

 

[johansen]

Many Vfds do not make clean 3 phase sine waves especially below 20hz, and they apply extra volts to get the motor to run. So the transformer will be somewhat saturated below 30hz for most vfd nominal programming.

If you ran the machine at 60hz and the tx still buzzed then there is something weird going on.

Is the 220v side of the transformer grounded in any way?

If you want to get rid of the noise then put a line load reactor between the vfd and the transformer, and put delta connected capacitors on thr 22v side of the tx

 

[Mannyv]

a vfd isn’t that complicated there are plenty of videos for it, if I can set one up to run everything on my lathe including tail stock and except the 3 ph. coolant pump which I’m working on now by adding a capacitor because a vfd can only run one motor at a time unless there all the same anyone can do it.

 

[SteveEx30]

You asked for a simple method, yet sounds like you wanted the cheapest method.

 

[DaveKamp]

... I ended up using a 7.5hp VFD (it was given to me without instructions).... 3 phase 220v came from the outlet to a power disconnect on the machine, from there it went to a 220-440 transformer... I hooked up the VFD ahead of the transformer, the transformer buzzed like one powering a large building.

Pardon the trimming, I did that to simplify and clarify how you had it set up.

So you're taking incoming 240v single phase from your utility panel, feeding the VFD, then using IT to drive a 240-440v transformer, which powers the spindle motor?

The VFD's intended home, is with it's 3-phase output connected directly to the motor's leads... and the VFD's control inputs or panel are within operator's convenient reach, where the motor's speed, direction, and run state can be chosen.

AC power Transformers don't like square-ish waves, they like sine waves, and VFDs tend to be closer to a Tetris game than Simple Harmonic Motion. They also REALLY don't like to be driven at some frequency other than their design frequency... they become improperly tuned low pass filters at least, and fuses at worst.

If that transformer's purpose was to step up the incoming 220 to 440 for the motor's sake, do this:

If I have this interpretation right, the best way is to return it to how it WAS... with the house 220 through the big hand switch, to the transformer, disconnect the transformer's output (which is stepped up to 480, right?) Acquire a 480v VFD, connect that 480 THERE... and connect the VFD's OUTPUT to the spindle motor... and mount your VFD's remote controls (run forward/STOP/Run reverse, and the speed potentiometer) to a pendant up at the operating location. As a bonus, connect a braking resistor to the VFD's dynamic brake terminals, and set the programming parameters to enable it at some reasonable level. The machine will be much quieter, much more powerful, and much more reliable... you'll certainly like it.

And I'm not knocking 'ya down for doing what you did... the four-letter F word (Free) is always a good word in MY shop, but the cool part about your circumstance, is that if everything is as I understand, you're in an excellent position, as good surplus 480v drives are significantly less costly to obtain, than the 240v one you were given... you can pull it off and save it on the shelf for the next machine you need to convert!

 

[JST]

I don't think it is as bad as all that.

As inductive devices, transformers will be fine over a range of frequencies IF there is a V/F compensation. VFDs normally do have that, because motors need it.

And, the days of square wave VFDs are past, at least all the current ones I know about have PWM sine wave output. Unless particularly evil as to frequency, that won't be a problem, and likely will be better at low frequencies than at high. I do have an old square wave ("quasi-sine") solar inverter, which runs most everything very well, transformer or not. (Certain battery chargers, having capacitive dropping, will not work).

The issue with transformers is usually at the high end, since the ones made for mains frequency will become lossy and inefficient at higher frequencies. Usually you will not be operating that high, but it is a consideration.

That all said, I also vastly prefer the idea of supplying a high voltage VFD with the high voltage, and not having a transformer on the output. It's a variable I prefer not to deal with.

 

[johansen]

a vfd isn’t that complicated there are plenty of videos for it, if I can set one up to run everything on my lathe including tail stock and except the 3 ph. coolant pump which I’m working on now by adding a capacitor because a vfd can only run one motor at a time unless there all the same anyone can do it.

A 7hp vfd running a say a 5hp lathe motor should be able to handle a 1/2 hp coolant pump switched manually in parallel, provided the lathe is not under heavy load when the 1/2 hp motor is switched on.

That being said a few weeks ago i bought a 1/2 hp fuji vfd for 50$ on ebay.

 

[JST]

A 7hp vfd running a say a 5hp lathe motor should be able to handle a 1/2 hp coolant pump switched manually in parallel, provided the lathe is not under heavy load when the 1/2 hp motor is switched on.

That being said a few weeks ago i bought a 1/2 hp fuji vfd for 50$ on ebay.

Yes, it should. But the pump will have the same power frequency as the spindle motor. That might be an issue if the spindle is speeded up or slowed down significantly.

 

[johansen]

Yes, it should. But the pump will have the same power frequency as the spindle motor. That might be an issue if the spindle is speeded up or slowed down significantly.

Thats what the gears are for...

 

[JST]

Thats what the gears are for...

I agree. I don't find the need for such fine speed control, myself.

But, a VFD is often used for speed control, as well as simple 3 phase conversion. People have the VFD, so they want to "use it".

If you start mucking with speed via the VFD, the pump gets the same speed change.

 

[aribert]

If the OP's jig borer is about 1.5 hp, and speed regulation is not required, could one not get a 5 hp static converter and a 5 hp, 3ph idler ( combined to be a crude rotary) wired to the static and the borer ?