Electronics > Projects, Designs, and Technical Stuff
BSP100 mosfet blows open, not short
jbb:
Yes. Sorry.
The ABB application was in High Voltage DC power converters, where you connect a whole heap of 6.5kV (or thereabouts) in series to make a composite switch rated at 150 kV at a thousand amps or more. An open circuit would be Bad News here because it would arc like nobody’s business. So instead they use more switches than necessary and accept some short circuit failures.
The converters include special gate drive and snubber systems which distribute the off voltage evenly across each switch.
T3sl4co1l:
--- Quote from: james_s on September 19, 2019, 07:42:47 pm ---I've seen blown bond wires a couple times but it has been rare for me.
I'm all too familiar with shorted mosfets causing a cascading failure. I had a washing machine motor controller that blew up every IC on the board including the ASIC running the whole show. It's the reason I'm not really a huge fan of non-isolated gate drive ICs.
--- End quote ---
I got a good one for you, yesterday -- I made a control board using a PWM chip (internal 5V reference), and the inverter with a Hall effect sensor for power measurement. Well, in one test I grenaded the inverter; as it happens, the transistors failed silently (stage 3 failure), and fault current flowed from the filter caps into the transistors through the sensor. The sensor is the only part that exploded! Conveniently, said sensor was powered by the PWM chip's 5V reference (the circuit is 12V otherwise), and it happened to take out both!
Tim
james_s:
--- Quote from: jbb on September 20, 2019, 01:26:54 am ---I once blew the silicone potting gel out of a 1700V 1200A IGBT module. It was very loud and messy. (I was glad to be behind a blast shield and wearing earmuffs for that testing.)
--- End quote ---
That's something I have always liked about power electronics, when something goes wrong it tends to be pretty exciting! Unfortunately it also tends to be expensive. :(
jbb:
Many's the time at my current job where I've wished for a nice clean 'bang' type fault, instead of the elusive intermittent bastard type fault.
On the other hand, I don't have to fill out safety paperwork, and the last thing to make clouds of smoke was the kitchen toaster.
Circlotron:
If only the nice clean ‘bang’ you speak of was limited to the power device instead of snaking it’s way through the board. :palm:
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