The Boost converter is designed for input voltage 72V and Output Voltage 210 V. The MOSFET Switch is getting damaged with in 2-3 minutes.
We are using IRF 840 MOSFET(44A, 550 V), 1 mH inductor on ferrite core, 1000 Micro Farad 250V capacitor. The current waveform is having spikes. We have not used any type of protection. Kindly suggest how to overcome this problem. The load is resistance 400 Ohm. View attachment Circuit.doc
does the diode fail too? if not, it is the layout that is killing your fet, you show no decoupling near the fet, or low Z caps (e.g. 1uF polypropylene) near the o/p diode to gnd, if the gate drive is really poor, this can affect things, it may pay to reduce the turn off speed if the volt spikes are too great and you cannot improve your layout ...
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poor or no heat-sinking of the fet (and/or diode) will kill it in minutes too ...
I must assume you did not go through existing threads dicussing similar problems.
Why does a Mosfet fail:
* overvoltage, even short spikes
* overcurrent
* overtemperature. Either short time according SOA or long time.
---> we ar not able to verify this with your given informations.
Thus we need
* your schematic,
* your PCB layout or a photo of your circuit
* additional informations about your current and voltage waveforms, timings...maybe by scope pictures