Building A Variable Frequency Drive For A Three-phase Motor

Here are the power and driver boards that [Miceuz] designed to control a three-phase induction motor. This is his first time building such a setup and he learned a lot along the way. He admits it’s not an industrial quality driver, but it will work for motors that need 200 watts or less of power.

The motor control board uses an MC3PHAC driver IC and an IRAMS06UP60A handles the power side of things. The majority of the board design came from studying the recommended application schematics for these two parts. But that’s far from all that goes into the setup. Motor drivers always include levels of protection (the whole reason to have a driver in the first place) and that comes in several different forms. [Miceuz] made sure to add EMI, over voltage, and over current protection. He discusses all of these, sharing links that explain the concepts of each.

23 thoughts on “Building A Variable Frequency Drive For A Three-phase Motor

  1. I was asked to produce something like this over the summer for a small scale investigation into the effects of power line harmonics caused by using VFDs on large (15MW) electric compressors.
    Ended up buying a commercially available unit, wish id seen this first :(

  2. Excellent find! Not only useful for 3-phase mains motors, but VFDs are essentially the controllers used to run turbomolecular vacuum pumps! (albeit at lower voltages and much higher frequencies)

  3. I have never seen a 3 phase motor that uses less than 1 amp, or about 340ish watts? The smallest commercially available VFD that I have seen is 1/4 of a HP or so. They are available used or surplus for perhaps $30 or so on ebay and are fully featured industrial controllers. Awesome build though!

    1. I used to use a rotary phase converter on my lathe. Sucks too much power and the output is not as smooth as true three phase. I now use either VFDs or brushless servos on everything.

      For the price of commercial VFDs on the market is it hardly worth building your own. Especially if you want something reliable. Teco makes some cheap ones, but there is a lot better stuff out there with flux vector capabilities.

    1. Bigger IGBTs, more careful drivers and driver balancing, more capacitors, capacitor precharge and protection, more snubbering, higher bandwidth control loops, faster current measurement, de-sat protection… As I mentioned above, it gets hairy fast and that’s if you’re still interested in a straight V/Hz drive. If you want to do sensorless vector/flux vector/encoder control then you’re in for even more fun.

      This is a great project, and I grabbed a copy of it just to see how be built it, but don’t start playing with bigger currents until you’ve got a really good handle on what you’re playing with. VFDs can get unstable really fast and you end up with the IGBTs blowing, with the caps right after them. It’s loud as hell and if you head or hands are anywhere in the vicinity, you could get hurt really bad.

      1. Thanks for the cautions, Andrew.

        Do you have any advice, in addition to getting very familiar with the controller’s behavior before scaling things up? I’ve built 3-phase BLDC controllers, which were designed to drive small CNC mills (motors no larger than your hand), but nothing of this size or magnitude yet. Are there better protection schemes or precautionary measures you can recommend?

        That said, this project does indeed look very interesting, and I’m compelled to build & improve it. :)

  4. Hoping to use simulink with some motors to learn with! But just to wrap my head around so the basic idea when it comes to motor types and motor control..

    In terms of constant v/f scalar.. does this include driving BLDC/PMSM with trapezoidal/sinusoidal current? It’s closed loop if using hall sensors for feedback? Are all “DC Motors”, either BLDC or PMSM, simply converting DC into AC internally to achieve the trap/sine commuation?

    In terms of Vector control… what is the difference between FOC (Direct and Indirect) and Direct-Torque Control (Space Vector Modulation and Direct Self Control)? Can FOC (and DTC?) be used on both BLDC and AC Induction Motors? Is FOC/DTC for BLDC/PMSM sensorless? How does Space Vector Modulation (SVM) fit in this?

  5. Do you think I could use this to feed a 3hp AC motor? I want to feed it 45 Hz instead of the standard 60 Hz and I don’t want to buy a commercial AC adjustable frequency drive.

  6. Need a inverter board for GE 3-phase washing machine motor.

    Hopefully can reuse some of the components such as it’s 2 large electrolytic capacitors, 6-heavily heat sinked power transistors. It has a 28-pin surface mount IC that has a small crater in it. Been reading a lot about GE HYDROWAVE washers.

    Don’t bypass the lid switch. If 4 cycles are completed without the unit sending the lid switch being opened, it disables the motor. You must have access to info in service manual to get the washer in “Service mode.”. They keep talking about a surface mounted LED on top of the inverter board made on square PCB mounted on top of motor under a metal top.

    Just got a very close look at my board. No LED.

    THE DESIGN Has a winding of wire & a gear in shape of a short hollow cylinder with gear teeth on top, when solenoid coil is powered, the gear is forced up during agitation cycle only. Down unenergized position for spin cycle.

    The coil is wrapped around a white plastic spool with a small fuse in series. The exposed portions of spool are protected by fiberglass tape. My coil was open & saw YouTube video on how to repair.

    This assembly is called the mode shifter assembly. NOBODY sells a replacement coil or fuse. The coil’s metal housing is RIVITED to the assembly. No problem, can drill out & fasten with bolts & nuts.

    3 hours later, a little upset & very sad. GE must have seen the video & started needlessly using excessive amounts of epoxy on my solenoid winding, now all busted up & damaged enamel wire. GE wants $150.00 to replace the assembly.

    Regardless, need to be able to power the motor to start. Oh,. You can’t get the inverter board separately either, comes with motor only, over $250.00.

    No really go to Wikipedia and look up washer & what it says about today’s models being planned (Engineered) obsolescence.

    Suggestion (preferably positive) to


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