Problem with MOSFET on the ESC

Thread Starter

joelsurfer

Joined Apr 25, 2022
7
Hi there, i´ve dimensioned the next circuit to control a bldc motor which would require 32A or more with load and instead of being 12 V is 24V. I have changed the mosfets and some of the BEMF resistors so that the arduino has a maximun 5V entry. Well, today i have done a test (without any tupe of load) but my mosfets had burned. I´m attaching the datasheet of the mosfets that i have used. I don´t know what could happen to burn the mosfets (they are able to handle till 46 A, +-30V). If anyone can help me i will be grateful.
 

Attachments

ronsimpson

Joined Oct 7, 2019
2,167
I see things wrong.
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With no load too much heat, the problem is "shoot through". You need to turn off a MOSFET, wait 200nS then turn on the other part! (on both edges) The IR2101 allows you to turn on both the top and bottom MOSFET at the same time. You must add some "dead time".
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100 ohms on the Gate? Try 2 to 10 ohms. Your AC losses will be too high with a slow 100 ohm resistor.
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You are using 650V MOSFETs. That is OK but 30V through 100V would be much cheaper. Look for 50V parts.

You are using 95m ohm MOSFETs that are rated for 35A. For the moment forget about AC losses and look at only DC losses. 35A x 35A x 0.095 = 113 watts. You will need a very large heat sink. You will lose 3.3V across the MOSFET.

I do not know this motor. A motor rated at 35A run current probably will need 100A to start up.

I searched digikey.com for MOSFETS, N, 75 to 200A, 30V to 100V in a TO-220, <2.5 gate turn on voltage.
I randomly picked PSMN4R3-30PL,127 which is 100A 30V 4.3m ohm, It looks like it will handle 100A at 3.5V of gate. (5V drive is better) DC loss = 5.5 watts. Needs a heat sink but better.

PSMN1R1-30PL,127 is 30V 0.0013 ohms. 200A Now we are at 1.5 watts. small heat sink.
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You defiantly have shoot through. You need low voltage, high current MOSFETs. (low Gate turn on voltage)
 
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Thread Starter

joelsurfer

Joined Apr 25, 2022
7
Well, first of all thanks.
;)

I have done a phase of the squematic with the components that I have rally used. I´m attaching the file behind.
Apart from the notes that I take on the photo I would like to be recommended about this items.

1. The resistance that goes to the driver is 100 ohm but you told me that it isn´t the most apropiate value. you recommend me10 ohm for each MOSFET no?

2. I tried some days ago this circuit modifying the value of the C13 capacitor. I just try the circuit with a program that putted 'HO' (HIGH or LOW) and 'LO' (HIGH/LOW). Well, I putted some capacitor with more value, 10 uf and 33uf for example. Firstly the voltage of the high side MOSFET in the gate was about 24 V more or less, but instantly decreased, the lower the value of the capacitor, the faster it fell the voltage on the gate. This can lead on what someone told me, the program really turns off the high side MOSFET but physcally it is really slowly decreasing his value instead of putting off instantly. This can lead into a short circuit between the two MOSFETs.

3. Someone told me that I could supply the driver with 12V to be in the apropiate operating range of the driver supply. I dindn´t do this so as to not to put a buck converter and so, supply all the circuit with 24V.

4.The Vgs of the MOSFet you tols me are +-20V. I wouldn´t have any type of problem no ? I thought that as I´m supplying the MOSFET with 24 V the VGs had to be at least +-24V.


Tell me what you think, thanks!
:)
 

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ronsimpson

Joined Oct 7, 2019
2,167
24V is too much for the IR2101. Most MOSFETS are +/-20V and some +/-30V. You can use a linear regulator.
1655814206774.png
You chose the wrong type of MOSFETs. You want low voltage high current. Please look at your dc losses.

the value of the C13 capacitor
How fast are you switching? 22uF is very large so I think you are switching at 60hz. What type of capacitor are you using? We normally use a small ceramic cap very close to the IC and the 22uF is in parallel. (0.1uF//22uF) C10 also.
 

Audioguru again

Joined Oct 21, 2019
4,798
A motor is stalled when it begins turning. The 32A is probably the running current, not the much higher stalled current.
The 36A Mosfet you selected can pass 36A only when its case is cooled to 25 degrees C which is impossible unless you use liquid nitrogen. With a huge heatsink plus fan maybe it will survive 20A. Use much higher current Mosfets instead of high voltage ones.
 

Thread Starter

joelsurfer

Joined Apr 25, 2022
7
24V is too much for the IR2101. Most MOSFETS are +/-20V and some +/-30V. You can use a linear regulator.
View attachment 269914
You chose the wrong type of MOSFETs. You want low voltage high current. Please look at your dc losses.


How fast are you switching? 22uF is very large so I think you are switching at 60hz. What type of capacitor are you using? We normally use a small ceramic cap very close to the IC and the 22uF is in parallel. (0.1uF//22uF) C10 also.
Sorry for mi letter! It´s not 22 uF, it´s 2.2uF.
 

Thread Starter

joelsurfer

Joined Apr 25, 2022
7
Well, so first of all, would you recommend me to put a buck converter and supply de IR2101 with 12V or to change that driver for another one with internal deadtime for switching and ensure that both MOSFET are never 'ON' at the same time. If you would recommend me the 2nd option, which driver would you recommend me?
Thanks.
 

ronsimpson

Joined Oct 7, 2019
2,167
I think you have a 24 to 5 switcher. You could change it to 24 to12 and then add a LM78L05 to make 12 t0 5. If the micro is low power.

For dead time, you can change the program to have more dead time. Or choose a different Gate Driver that forces dead time.

There are no pull-down resistors on the Ah, Al ,,,,CH, Cl lines. At power up the micro probably has the pins in tristate mode (or input mode). I think there is a chance these lines will not be at 0 and turn on some of the MOSFETs. Add 100k resistors to ground. After the computer is up and has set the pins to "0" and output, then this problem is OK.
 
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