Controlling a Single Phase Motor (Refrigerator Compressor) using PWM

[flio098]

we want to amplify the amplitude because we discovered something in our simulation. PWM input to an IGBT (we used IGBT to function as a switch w/ PWM as the input to its gate) we plan to let a 220VDC through the transistor and it will be switched on and off through PWM. What we discovered was if our PWM input was only about 5-10Vpp the voltage that the IGBT lets through was approximately 5-10V as well... so we changed the PWM to about 100Vpp and then suddenly the voltage that comes through became 199-215V...

Is this a concept in a transistor?

 

[flio098]

Alright Thanks! um do you know any schematic on how to drive an IGBT? i believe that its the current that counts when you want to turn on the device, is that right?

 

[MikeMl]

Here is a low-side IGBT gate driver that I built into my airplane mover. It uses a 1/4HP 130Vdc GearMotor. I am using a PIC to PWM it at about 10kHz to smoothly control the acceleration/deacceleration. Picture here.

The green trace is the current into the gate of the IGBT. It takes a driver with a current drive of ~1/2A to rapidly charge/discharge the IGBT gate capacitance.

 

[flio098]

Hi MikeMl thanks for the schematic! our group is trying to drive a motor with an H-Bridge configuration... I also tested your circuit and it works fine when the load (i just used a resistor) is in the COLLECTOR side. I tried transferring the load to the Emitter side and the voltage output was very low. Is it really like that?

Thanks!

 

[flio098]

how do you post images, it says here it needs a URL link? does it have to be in tumbler or websites like that? (we are new here sorry)

 

[Nigel Goodwin]

how do you post images, it says here it needs a URL link? does it have to be in tumbler or websites like that? (we are new here sorry)

No, post the picture here - click on 'Go Advanced' and then on 'Manage Attachments"

 

[MikeMl]

Hi MikeMl thanks for the schematic! our group is trying to drive a motor with an H-Bridge configuration... I also tested your circuit and it works fine when the load (i just used a resistor) is in the COLLECTOR side. I tried transferring the load to the Emitter side and the voltage output was very low. Is it really like that?

Thanks!

Read the Name on the schematic I posted: LOW-SIDE DRIVER! It drives the gate of the FET/IGBT to 12V with respect to its source. It was never intended to be used to drive the high-side of an HBridge.

Why are using an H-Bridge, anyway? Don't you just have a DC motor that always turns one one way? You only need an H-Bridge if you are reversing the motor.

 

[flio098]

We plan to apply it to an AC Motor, is it not applicable? Another question, doesnt an IGBT acts as a switch? so when it turns on, it sort of turns into a closed switch where it will let voltage flow from collector to emitter? Thanks

 

[flio098]

This is the circuit that we simulated, the 500ohm is like our "MOTOR" and we switch the igbt's on and off correspondingly for it to become an AC.

 

[tcmtech]

So once again why are you ont just using common high/Low side driver IC's to run your circuit?

View attachment IR2110 - IR2113 HALF BRIDGE DRIVER.pdf

 

[MikeMl]

You were told in the first three posts in this thread that this entire enterprise is a fool's errand.

The project has become: Lets learn how to make a Variable Frequency Motor Drive controller[/I]. If I really thought I needed a VFD, I would just buy one.

 

[flio098]

That would be nice, but we are not allowed too.