# MOSFET burns - 220V inverter for induction motor speed control using Arduino.

#### Claudez

Joined Mar 24, 2019
28
The probes ratings is also 300V

#### 1206.sachin

Joined Oct 3, 2019
2
Once i turn ON the power, the MOSFET explode. And gate driver fails too.
Actually 4n35 is slow, but I archived fast turn OFF but pulling it’s gate to emitter by 10k ohm. And i check the waveform with the oscilloscope, it is pretty well.

Here it is.
Run system at 24 volts & take waveforms across MOSFET. Then you can extrapolate those waveforms for 310 Volts .
Add RC Snubbers @ 310 volts it is must.

#### Irving

Joined Jan 30, 2016
3,313
For engineering purposes the ionisation point of air is usually taken as 1kV/cm depending on atmospheric conditions etc but many cheap/small eg 1/4W resistors are rated at 200 - 250v. Its common practice then to use a string of them to limit the voltage across any single resistor. Some more expensive types, eg Ohmite, are rated at 500V or 1kV so you could use fewer but at £1.80 ($2.50) each that's expensive. Historically the 'general rule of thumb' was 5:1 though I can't cite a specific source. So a minimum of 5 resistors to make 99Mohm. 20Mohm are hard to find so I use 10Mohm, needing 10 resistors. Does that make it clear? Just because the probe is rated at 300V doesn't mean you should rely on that. For both these HV probes the HV end is a custom heavily insulated cable/probe. I wouldn't use a 300v tip on a 1kV circuit.. #### Irving Joined Jan 30, 2016 3,313 Run system at 24 volts & take waveforms across MOSFET. Then you can extrapolate those waveforms for 310 Volts . Add RC Snubbers @ 310 volts it is must. Hmmm, I'm not sure about that. At 310v Vds the impact of the charge through the drain-gate capacitor on the switching time is very different to that at 24v... Thread Starter #### Claudez Joined Mar 24, 2019 28 For engineering purposes the ionisation point of air is usually taken as 1kV/cm depending on atmospheric conditions etc but many cheap/small eg 1/4W resistors are rated at 200 - 250v. Its common practice then to use a string of them to limit the voltage across any single resistor. Some more expensive types, eg Ohmite, are rated at 500V or 1kV so you could use fewer but at £1.80 ($2.50) each that's expensive. Historically the 'general rule of thumb' was 5:1 though I can't cite a specific source. So a minimum of 5 resistors to make 99Mohm. 20Mohm are hard to find so I use 10Mohm, needing 10 resistors. Does that make it clear?

Just because the probe is rated at 300V doesn't mean you should rely on that. For both these HV probes the HV end is a custom heavily insulated cable/probe. I wouldn't use a 300v tip on a 1kV circuit..

Alright, Thank you.

#### Claudez

Joined Mar 24, 2019
28
Hmmm, I'm not sure about that. At 310v Vds the impact of the charge through the drain-gate capacitor on the switching time is very different to that at 24v...
I think so, because I tested my circuit with 20ish Voltages and the waveforms were good I couldn't notice much of the issues, but once I apply 310V, boom!

#### hyu2123

Joined Jan 5, 2008
4
Hello Claudez,

My suggestions:

++ Connect the Shutdown SD of the two mosfets drivers with an RC circuit to initially be the driver OFF. ( Like a Reset circuit)

++ Also connect pulldown resistors 10k to the four mosfets.

I also had this same problem (with low voltage it worked but when connected to high voltage ... Kaboom).

You can see this modification in an Application note from Microchip AN889

Check page 18 for the schematic

You can test this modifications connecting in series with the line wire a filament bulb

Good luck!! And be safe!!!

#### Claudez

Joined Mar 24, 2019
28
Haha, Thank you. The SD pin of the driver is for shutdown as you say, as i remember from the data sheet, should be high to shutdown and low for the driver to work, can you a bit explain to me how will the RC circuit be used as a reset?

Alright, i, I’m adding 10K pulldown resistor, Thank you.

#### hyu2123

Joined Jan 5, 2008
4
Hello,

The SD shutdown pin could be connected to something like this:

Source from https://electronics.stackexchange.com/questions/67767/connecting-the-reset-pin-of-at8051
(Reset in the image is your SD pin)

The capacitor is used to initially connect the SD to 5V, shutting down the driver IR2113

Another option: You could control the shutdown with your arduino using the pull up mode or connecting an external pull up resistor. And after a while, output a LOW with the arduino to activate the driver.

#### Claudez

Joined Mar 24, 2019
28
Thank you, May i know what is the reason for shutting down the driver at the beginning?

#### hyu2123

Joined Jan 5, 2008
4
Hello, I would say we never know what would happen in the startup transient with the logic circuit. So to be sure I disable it at startup and also the G-S pull down resistors help.

May be I am being too cautious haha.