I want to design a device to control a 0.5 HP to 3.0 HP three phase AC motor with single AC power.

I need to able converting single phase to three phase. Also an three phase ac motor controller should be added. Is there any IC and modules for helping me in this project?

  • \$\begingroup\$ Just to be clear, do you want to have such a thing, or to build one? Having one is easy, they sell them by the millions. Building one is an extremely broad question! \$\endgroup\$ – Stephen Collings Oct 26 '15 at 13:28

You can take a look at the various methods of building a phase converter and pick the one that fits your needs. This technology is very old and well documented even in the oldest handbooks you will find. You may find something smart and simple from e.g. 1960 that will work perfectly well.

The second approach is more straightforward: first convert AC to DC and then, using three synchronised and phase-shifted inverters, create three phase AC of any desired frequency and magnitude:

Similarily like that, but with three inverters

  • \$\begingroup\$ Thank you. Do you know any useful invert's module? I think i should control these inverts with a micro controller.So invert's IC should have this capability. \$\endgroup\$ – mehdi Sep 24 '12 at 14:01
  • \$\begingroup\$ Can you explain some of those very old methods? \$\endgroup\$ – Rocketmagnet Sep 24 '12 at 15:08
  • \$\begingroup\$ One of the most popular ways was to use an autotransformer, but I never read into it. This method was preferable, because anyone can wind up coils to create such a device using only wire and elbow grease. And this is another example of the (old approach)[en.wikipedia.org/wiki/Rotary_phase_converter]. \$\endgroup\$ – Jonny B Good Sep 24 '12 at 15:38

You don't say what parameter you want to control on the 3-phase AC motor. It could be voltage, speed or torque.

It sounds to me that you are describing a variable speed drive. These are readily available in a wide range of powers, etc. For smaller loads such as yours they are available with single-phase input and three-phase output. This makes them ideal for driving three-phase motors where only a single-phase supply is available. An additional advantage is soft start capability.

If you want to build your own make sure to provide proper isolation between the control circuits and the high-voltage side using opto-isolators. Some of the three-phase controllers will have the opto-isolators built-in. Be warned that the control strategy will be far from trivial.


What you want is a variable frequency drive, or VFD. This is a commodity part, easily available from a wide range of manufacturers and distributors. At the power levels you're describing, many are specifically designed to take single-phase AC in and put out three-phase AC out to a motor.

A quick Google search found these:




Now, if you actually want to design such a thing, that's much more complicated! You'll need to know how to design a rectifier, both electrically and thermally. You'll need to know the same about an inverter. You'll need to size the capacitors properly. You'll need a precharge. And that's before you even get into how you control a motor by feeding it voltage and frequency. This is very much not a trivial endeavor; there are several billion-dollar companies who do this for a living!

Not to say you can't or shouldn't do it. Just know that it's an investment of months or years into making something that you can buy for $300. If you succeed, you'll be much smarter! Just make sure you understand that that's your goal when you start, and not necessarily to be cost-effective.


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