Have a chance to pick up a Ronk

I got a call about a couple of used Ronk converters. I haven't seen them yet, but were running when taken out. They are model 80A........looked up the Ronk site, but doesn't look like they still make that particular model. From the description I got of them, they are pretty heavy, like 100 pounds or more. That is kind of heavy for just a static converter, would it be a "phase shifter" model? One is a 10hp model the other 20hp

Likely they are actually Rotary Phase Converters.... RPCs

They are most likely an early type transformer type static converter.
Known as the Ronk Add-A Phase.
Here's a copy of an early manual page showing a model 64A


I believe that these early models are comparable to the current type S, and are intended for a single motor load. I would call and check with Ronk to see if they are suitable for your intended application, and if they have a manual for balancing them. They need to be adjusted to the load.

ADD-A-PHASE - Static Phase Converters - Ronk Electrical



SAF Ω

Sounds like they have a transformer in them, because they sure aren't rotary. So that would mean they actually produce constant voltage on the third leg?
They came out of a water treatment plant in a one horse town, literally a wide spot in the road, so no three phase power available. I was told that they were running two motors off of each.
I was hoping from what I was told and what little I could find, that they were phase shifters, since it is obvious they aren't rotary

You said the magic words "water treatment plant", so yes, I think you folks are right, they are the transformer type.

That type is really only good for a constant power load. Water pumping that operated continuously at one load is a perfect application, so irrigation is typical, but a treatment plant could also have a constantly operating pump like that.

It would not be very helpful for most machine tool loads. .

rj1939,

The Ronk Add A Phase is a static auto-transformer converter. Sounds like that is what you have. The Add A Phase has a heavy auto-transformer in the box, the Phase Shifter is just a box of relays and capacitors. Add A Phase will provide full rated horsepower. As has been previously noted they are tuned to the motor for full horsepower (by adjusting the running capacitance and transformer voltage). At full load the leg amps will be equal. They can be run at less than full load as in machine tools since, although not balanced, none of the leg amps will exceed the FLA of the balanced condition.

Prior to the introduction of reasonable cost VFD's I built a number of these auto-transformer converters (same circuit as Add A Phase) for the machine tools in my shop. They have provided excellent trouble free service.

Here is an interesting FAQ about the Add A Phase.

Ronk Static Phase Converter FAQ

The Add A Phase conversion method has been discussed at length in this Forum. If you are interested you can check out this thread and the links posted in it.

https://www.practicalmachinist.com/...-conversion-103057/?highlight=autotransformer

Joe

Thanks Joe..............that gives me some more info than what I have otherwise found. I've got some reading to do on that previous thread. Wasn't aware of the limitations of auto transformer setups til now.
Had done a search on Ronk converters and had quite a few hits, but didn't notice that one.

Finally got a chance to get a picture of said converters................no doubt, they are of the auto transformer style.


Aside from running pumps, they would be suitable for running an air compressor, it seems to me. That is about all that comes to mind.

rj1939,

For 30 years I've been running a 175psi air compressor, 5hp table saw, 1 hp morticing machine, 13" metal lathe with a 2 speed motor, Belt/Disc sander,12" wood planer, 8" wood jointer, 18" band saw and a 20" band saw on home made autotransformer converters with the same circuit diagram as the Ronk. Use it with any machine or wood working tool within the rated capacity. You can used it at less than rated capacity by adjusting the transformer taps & capacitance.

I see you are from southern Ill, not surprising you found add a phases in that area. The Add-A-Phase was originally made by the System Analyzer Co. in the 1950's for running oil pumps in southern Illinois where 3 phase power was not available. Ronk bought the company and continues to sell the Add a Phase.

Joe

Joe, do you know why they use a dual core winding, versus the homebrew single core models?

SAF,

The Ronk has an expensive custom wound auto-transformer with taps for adjustment to the voltage to the run capacitors. I suspect most of the cost of the converter is the transformer. I assume their configuration suites their manufacturing requirements. It's all about raising the voltage to the run Cap.

If you calculate the voltage required to the run capacitor you will find for most motors 7.5 hp and under you will need (230 base V) very close to 460 v for a 3600 rpm motor and 345 v for a 1800 rpm motor. The voltages are determined by the motor's Power Factor.

For a home-brew version any 240/480 to 120/240 isolation power transformer (all coils encapsulated in a metal box) can be wired as an auto-transformer to provide the required voltages. For 1200 rpm and lower a buck-boost transformer can be used. Then you only adjust the run Cap for balance. The Add a Phase provides much better adjustment capacity by use of the transformer taps and capacitance adjustments.



Joe