four switch inverter as driver for three phase induction motor

[sally6]

I have set up a system use 4 IGBTs for an inverter that will drive a 3 phase induction motor in a simulation using PSIM. The output of the 3 phase should use 6 IGBTs, but I'm using 4 IGBTs and connecting the other phase with 2 capacitors. However, the current from these 3 phases is unbalanced. The phase connected to the capacitor cannot match the others. I feel the mistake I made is in the oscillator circuit I created. Are there any other suggestions for this issue? Or any other advice on how to learn PSIM software for the oscillator circuit in a 4 IGBT inverter to drive a 3-phase induction motor? I would appreciate any opinions on this problem. I'm open to other ideas as well. Thanks.

 

[wayne440]

Claiming no expertise, I will venture a guess that the phrase "...The output of the 3 phase should use 6 IGBTs..." defines the root cause of your issue.

 

[sally6]

The root of the problem is when I start the simulation using PSIM with 4 IGBTs and 2 capacitors, it doesn't produce a balanced current output. Here, I need to learn about the oscillator circuit used to control these IGBTs. Do you have any suggestions? Thank you.

 

[BrianPetersen]

Also claiming no expertise, it seems to me that supplying 2 of the 3 phases to the motor via active control components (IGBTs) and one via passive devices (capacitors) is inherently going to supply unbalanced current. Maybe you can find one specific speed and motor load at which it balances out, but any other speed and load it will not.

Maybe there's a reason commercial VFDs are not built that way. Maybe you're finding out what it is.

I am absolutely not an expert in this, and am quite open to be proven wrong by someone who knows more!

 

[sally6]

have u ever do a c block in psim that contain codes switching sequence for output 3 phase from the input 1 phase? i think the mistake i made in coding input.