Timeline for Brushed DC motor control MOSFET selection
Current License: CC BY-SA 3.0
16 events
| when toggle format | what | by | license | comment | |
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| Oct 9, 2014 at 14:13 | comment | added | KyranF | it is not really the best thing to just keep up-rating the device. Remember, these things can handle 4-5x the current for short durations (pulse current ratings) such as a load change, and the motor is an inductor itself which naturally limits current surges.. | |
| Oct 9, 2014 at 14:11 | comment | added | KyranF | @siva for your next attempt, I say use two in parallel with each their own heat sinks, and try to put a heavy duty 200+V, ~3-10A rated flyback diode across the motor terminals. | |
| Oct 9, 2014 at 14:10 | comment | added | siva | But my doubt is in what factor should I increase these ratings. | |
| Oct 9, 2014 at 14:09 | comment | added | siva | Yes, I saw that post, I probably should increase the mosfet ratings since the measured mosfet junction temp is 80.c which will further derate the Max Id allowed(can be seen inthe datasheet) and also I noticed the failure of mosfet happened only when there is sudden increase in load and increase in load will lead to sudden increase in current and then mosfet failure. | |
| Oct 9, 2014 at 13:52 | comment | added | KyranF | @siva see this question and it's answer on this site: electronics.stackexchange.com/questions/63568/… | |
| Oct 9, 2014 at 13:47 | comment | added | KyranF | @siva perhaps that was the over-voltage transient, that can cause FETs to fail into short circuits. Try diode clamps. | |
| Oct 9, 2014 at 13:43 | comment | added | siva | During the failure the Mosfet DRAIN and SOURCE pin gets short.Yes ofcourse it get hot, which is why I have put a heavy sink and I have measured the heatsink temperature which is 70.c (max).The duty cycle goes upto maxium of 75%. | |
| Oct 9, 2014 at 13:33 | comment | added | KyranF | @siva it seems your mosfet is good enough, do you know what was happening during the MOSFET failure? And did your first FET get very hot? what duty cycle % does your controller output usually, when you reach the desired speed? | |
| Oct 9, 2014 at 13:14 | comment | added | siva | I have further updated with the circuit diagram, with additional notes, have a look. | |
| Oct 9, 2014 at 13:01 | comment | added | KyranF | for example if you chose a 200V 6A MOSFET, you will very quickly have a broken device. | |
| Oct 9, 2014 at 13:00 | comment | added | KyranF | @siva It only takes one microsecond of things not being okay, to blow up ;) | |
| Oct 9, 2014 at 13:00 | comment | added | siva | I have already designed the circuit based on the ratings, and its running okay. | |
| Oct 9, 2014 at 12:58 | comment | added | KyranF | If you wanted to go for a higher current handling FET you can go for that FDP's big brother, the FDP24N40 or similar, which is 400V 24A rated, with the same package. | |
| Oct 9, 2014 at 12:55 | comment | added | KyranF | You can also put FETs in parallel for more throughput, but be aware that this also parallels the gate capacitors, making it even harder to turn them on quickly. | |
| Oct 9, 2014 at 12:51 | history | edited | KyranF | CC BY-SA 3.0 |
added 178 characters in body
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| Oct 9, 2014 at 12:43 | history | answered | KyranF | CC BY-SA 3.0 |