A small 3-phase inverter to drive induction motors

[danijel.gorupec]

I made a small, 1A, inverter to drive standard small induction motors. Read details **broken link removed**. Schematics, PCB layout and demo software are available.

The inverter is supplied by 230VAC, Uses IRF840 MOSFETs, PWM is at 15kHz, is pretty elementary and... is easy to build at home. It however lacks self-protection and motor-protection means... Anyway...

 

[danijel.gorupec]

I was advised to also include some resources in PDF form:

- Schematics: View attachment Schematic_ Inverter.pdf
- PCB layout: View attachment PCB_ inverter.pdf

 

[andre_luis]

Would be nice if you could attach some pictures of the output waveform.

 

[danijel.gorupec]

Sure... I used my cheap phone camera to make oscilloscope screen photos...

The picture below shows the voltage on one phase (measured between DC-bus negative and phase output). The connected motor is 150W induction motor and runs non-loaded.


The picture below shows the single phase current measured as the voltage over 0.54 ohm resistor (2 resistors of 0.27 ohm in series). There are spikes, but it doesn't look very bad. There is some offset that I don't know the exact reason.


The picture below shows the same current but zoomed-in so that effects of switching can be seen.


Finally, the picture shows the output voltage zoomed out at maximum motor speed (about 60Hz). Because high voltage amplitude is needed at these speeds, you can see that there are portions of the waveform where the PWM is stuck at 0% or 100%

 

[engineerpervez1]

Nice contribution