Transformer Converter? What is that?

Instead of an idler motor spinning away this type of converter uses a transformer. This approach was used back in the 1940’s and fell out of favor in the on going years.

Why did it fall out of favor? One reason was, transformers became more expensive and mass produced 3 phase motors were cheaper.

But there’s another reason;

Get your mind around this concept and you will understand the differences.

The transformer converter powers the motor that you want to run and there is a symbiotic relationship (Inductance/Capacitance tuned circuit) between the transformer. the capacitors, and that motor.

This puts power into your motor for starting and running at full power. So your motor is part of the whole circuit.

It’s different with the rotary converter;

The theory for the operation of the rotary converter is getting a bigger motor running and overbalancing it with capacitors to force the voltage up on the manufactured leg.

By using additional capacitors the voltages on two of the legs are force higher then the line voltage. Usually around 250-270.

Those legs are forced up because guess what happens? When you start and run your motor the voltage drops down. The idea is to raise the voltage so when it drops, it’s in the ballpark.

What you need to realize is this isn’t a big spinning generator, cranking out amps and volts. It’s a big spinning motor, that’s running on single phase power through the use of capacitors.

If the rotary converter manufacturer can get that motor running, why not just sell you that? Put that motor on your compressor? Why you could have a 50 hp compressor at home!

Well, the reason you can’t is that motor can not start or run anything. It’s just going to idle away all day.

You now have a 20 to 50 horse power motor running, and from that do nothing motor you are going to start your compressor!

The catch is they sell you an over sized converter. The extra large motor is not doing any work, so now there’s ‘surplus energy’ in the motor. You are stealing a portion of it to run your load motor. Simple right?

If that is the case why are rotary converters the ones manufacturers sell?

It comes down to two practical reasons; business economics and usability.

The rotary is a unified package. It comes as one unit. Okay, the motor and the control panel are sometimes separate but one electrically.

You don’t need to make any adjustments or fiddle with start relays. It can be connected up to a milling machine, lathe, or other machines with multiple motors, speed controls, reversing switches, etc.

No real user intervention needed.

The transformer converter is not one unit.

You have the transformer and then each motor has its own run and start capacitors and start switch.

You can run multiple motors, each one feeds off the transformer, but needs it’s own start and run caps. When you set it up, you are going to adjust the capacitance for the motor.

Because of this balancing, you can not run motors or machines that have complicated speed controls, reversing functions, cnc machines, etc. The transformer converter is for simple machines with one motor like air compressors, dust collectors, vacuums, pumps, etc.

So that’s it in a nutshell.

Selling the rotary converter is just easier for the manufacturer and they will recommend you buy one that is big enough to run all your loads.

That is why I stress so much on this site, that you need to know what you want to run. And how many, etc.

One point to make here is if you have a transformer converter and then have a machine that needs a rotary converter you can always hook up a do nothing motor to the transformer converter and now you have a rotary converter.

The transformer converter will work stunningly well in situations, but you need to know when to use it and why you are using it.

So what would be the use of the transformer converter?

Is there an advantage for the DIY person to build one?

The transformer works best in a few different situations:

Your motor is so hard to start the rotary would have to be way over sized. Evaluate the cost of an extra large rotary. Compare that to the cost of building a transformer converter for the one or two machines that need that extra starting power. Sometimes it is only your air compressor that has trouble starting.

If you have a machine that is going to be used occasionally throughout the day. No sense having a rotary running all day just so you can run a drill press or band saw once or twice in a day.

A machine like a pump or fan that comes on and off all day. Especially if the motor is real small such as 1/4 or 1/2 hp. Here the noise of running a rotary all day just for a small fan motor doesn’t make sense. Especially in 24 x 7 situations.

If this is a simple motor that needs to run at twice the input voltage: 380, 415, 480, 500. The rotary converter seems to lose some of its all ready weak starting power, when run through the step up transformer.

When you have a very big motor and a very small one. Again sizing the rotary for the big one is expensive and more noise and electrical use.

 

Made this transformer at home
Homemade transformer and capacitor box

If you want to save money and get out standing starting power. By shopping around for a used transformer you can have a converter that starts your drill press, air compressor, hydraulic press, dust collector, or any other simple motors. For a very reasonable cost. Size the transformer right and run as many motors as you want from one transformer.

On the left an image from one of my videos. The yellow thing next to the metal box is a homemade transformer. The box and the transformer start and run the vac with ease.

Here are some examples of a good situation to use the transformer converter.

The 10 hp vacuum cleaner is one. The cost of purchasing a 40 to 50 hp rotary just to run that makes no sense. The small transformer converter that I show in the above image starts and runs it just fine at the cost of a few hundred dollars compared to 4 or 5 thousand for the rotary. That vacuum is an extremely hard to start machine, a 55 hp rotary just barely got it running. During the years I used the vacuum cleaner, I found it very convenient to simply click a 60 amp breaker and the vac and transformer would be powered on together. I would vacuum and turn it off. Real simple.

On my You Tube channel I show a ten horse air compressor running and also show the inside of the converter box. Think of what it would take to run this compressor on a rotary converter. You would need a 30 hp rotary to run it, and start it reliably. That’s a massive motor running all day for when the compressor needs to start. You are wasting electricity. Think of your shop situation and think of how many hours your air compressor runs in an eight hour day. Sometimes that might be only 30 minutes to an hour.

My customers in the overseas countries had problems of skimpy, expensive electric systems, plus they had to double the line voltage. Those are the worst conditions for a hard to start load. They didn’t have the power to start a large rotary. I showed them how to build their own transformers to raise the voltage and start the motor with out the rotary. On the Ronk Industries page they mention the advantage of being able to raise the voltage with the transformer converter, in the same package, no extra transformer needed.

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