220 Volts DC Motor Control using IGBT and Arduino Mega with Optocoupler

Thread Starter

JMBA

Joined Dec 21, 2018
5
This is JMBA from the Philippines saying Good Morning to everyone! (11:59 AM | UTC+8:00 Manila Time Standard). I am a Computer Engineering Student and I am in deep trouble and need your help!

The whole point of this thread is to ask this: Why do you think this circuit failed?

We are graduating this school year, 2018-2019, and we made a thesis called: "ViReX-E | The Virtual Reality Exercise Equipment". It is a project where you will use an android phone with VR capabilities (Some phones doesnt have the function) to interface a VR game where you can walk on a treadmill but see different on the phone, simulating the experience as if youre walking on the virtual world with the same experience as you walk on the real world. The biggest downside of this project is it can only accomodate one direction of movement: Only Forward, but to use that as an advantage, we changed the scope from simulating an all capable vr world to being able to exercise in the vr world.

To see a bit preview of the project, you can visit this website. But I'm afraid I haven't updated it up to this date.
https://hackaday.io/project/161435-virexe-the-virtual-reality-way-to-exercise

Now my problem at the moment is regarding the design. To control the speed of the DC Motor (Max Rated 220VDC), I used an IGBT, FGA25N120. For reference, refer to the Diptrace Schematic below:
https://drive.google.com/open?id=1o1PsdpPP3Fx3-W1GJiY2FB1FhhU_CFaH

For those who do not see or can't open the Schematic, I included an image below:





I was still in testing phase, so I removed M2, M3, M4, and M5. The video below is the testing phase of the circuit:


As you can see in the video, the Treadmill run at the same speed when connected to 220VDC. The Test LEDs D8 and D9 never lit. PWM PIN [D2] was sending a 0% Duty Cycle. After the test run, Q1, the FGA25N120ANTD, had its Collector and Emitter shorted with 3 Ohms on either biases (Forward or Reverse). That's why the DC Motor kept running on 220VDC, Q1 was already busted right at that moment, the Collector was already shorted to the Ground, thats why the DC Motor was getting 220vdc at the moment.

My Arduino Mega is sending a PWM signal through D2. The Code is here
https://drive.google.com/open?id=1CebxuLfvB1ma5HS35T6kq_YHTi3Ty21_

I controlled the PWM Pin by sending A0 values from a 10K Potentiometer, dividing the 5 Volts and GND.

But I kept wondering why it broke. Is something the matter with my circuit? Why do you think my IGBT broke? Am I missing important pieces? Should I consider using a MOSFET? Please help me. I need to make this project possible, and I need your help guys :) Good day. You can also e-mail me, parekoy201@gmail.com
 

Sensacell

Joined Jun 19, 2012
2,544
Your IGBT will always be on, there is no current path to pull the gate to ground.

The gate looks like a capacitor, it's very high impedance at DC.
It's charging via the leakage current of the opto-coupler, even with zero LED current on the input.

You need to provide a discharge path for the IGBT gate, a resistor to ground.
Depending on your PWM frequency, you may need to re-design the gate drive circuit altogether.
A gate driver needs to be able to source and sink hefty currents to both charge and discharge the gate capacitance quickly.

Just using a resistor to ground will work, but the turn-off will be slow, causing high power dissipation in the IGBT.
 

Thread Starter

JMBA

Joined Dec 21, 2018
5
Hello Sensacell! Thank you very much for replying. I can see that the Gate will charge, and to clarify, are you saying that I should connect a Pull-Down Resistor to it (A resistor connected to the gate and the other to the ground)? Do you think the IGBT broke because of the leakage current? Sorry I am very new to this
\
 

Sensacell

Joined Jun 19, 2012
2,544
Place a 5K resistor gate to ground and try it again.

Note that the absolute maximum gate-to-emitter voltage is 20 V, your circuit is on the edge.

You should aim for 10 volts on the gate.
 

Thread Starter

JMBA

Joined Dec 21, 2018
5
I tried to connect a 7815 to regulate the gate voltage to 15Volts with my second IGBT IXGH32N60C but up to no avail, it also broke. It also ended up with 6 Ohms shorted from Collector to Emitter. But I will try that gate suggestion later on.

Also, I tried the IGBT without the Motor but with the LED (D9) but it was also working, but as you said, when the Vge was 0V, the Vce was 50VDC and the Vge was 15VDC the Vce was 220VDC.
 
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