Phase Converters and Motors - What Goes With What?

So, you're getting started on a new project and you require some guidance on converters and motors. Maybe you’ve never done electrical work before - or perhaps you’re a bit rusty and need a refresher. We know from our customers that sometimes certain projects require guidance; well, you’ve come to the right place!

At Electram, we specialize in power and electrical knowledge, and are happy to help our customers determine what they require for their power and electrical needs.

Common questions we get are:

“How much can I run on my converter?”

“Can I run two 50 hp motors on one 100 hp converter?”

The answers to these questions are not black and white, so let’s get into it.

How much can I run on my converter?

It is based on what type of load you have and to determine how big of a generator you need to have enough power to start and maintain your load. The question comes down to total ampacity of the converter. The ampacity of the converters are found on the plate with their maximum amps. It’s important to remember there are different types of converters, so be sure you choose the right one for your project.

What are Digital Phase Converters?

Digital phase converters are the new age of technology. It's an electronic box that you hang on the wall, your single phase comes in - your 3 phase goes out and you've got a computer making sure that the voltage balance is always equal.

What are Rotary Converters?

Then there are rotary phase converters, they are more difficult to size for a project. The rotary converter has a generator, which is a glorified electric motor converted to act as a generator instead of an electric motor. Basically on a rotary converter, the generator has a name plate with maximum amps on it, and in a perfect world you wouldn't run a motor with more amp draw then what your rotary generator has.

If you're going to operate a computer-controlled machine, like a CNC, you want to go with a digital converter as it will maintain the balance of the voltage - whereas a rotary converter does not possess that technology.

The main takeaway is that it comes down to the total ampacity of the load versus the ampacity of the converter. Basically, you look at the size of the converter and you don't run more amps on your machinery then the generator is rated for. It’s important to keep that in mind when looking to purchase.

Can I run two 50 hp motors on a 100hp converter?

Two 50hp motors will likely have a combined locked-rotor ampacity (LRA) that is higher than one 100hp. A 100HP converter will have a total output of 142amp. If the motors are on VFDs (variable frequency drive) then the LRA won’t be as high, or at least it can be controlled. As long as they have a soft start or a VFD then it shouldn’t be a problem. So the rule of thumb is you cannot run more loaded motor horsepower than the size of the generator you're utilizing, and that's basically a starting point.

If you’re looking for more information or guidance, please feel free to contact us as we’re always happy to help.

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