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Voltage Spike Problem

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PICMICRO

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I need to draw variable about of power from an Inductive Power source (small 3-phase alternator)

I am using 3-phase rectifier and an IGBT as switch. I am providing PWM signal to the IGBT, to control the Power drawn by dummy load.
But during the Turn-off phase of PWM signal, the Inductive source Produces a very high-voltage spikes, exceeding the rating of IGBT and blowing it.

Is there any work-around or effective protection?
 
Last edited:
strantor said:
View attachment 65268
goes across the inductive load, clamps spikes. There are several types that are well suited for the job. I have only ever needed to use general purpose/rectifier diodes but you may need something faster. I don't know, maybe others can advise.
https://en.wikipedia.org/wiki/Flyback_diode
Click to expand...
The problem is, the load isn't inductive, but the source is.
Now, can you please re-work on the problem and place the diode appropriately?
 
I would place a zener with voltage rating about 75% of the maximum IGBT collector-emitter rating from the collector to emitter. The zener power should probably be rated at least 3W. Add a small (0.1μF) cap in parallel to absorb the high frequency transients.
 
During turn ON, the IGBT will be drawing currents in the orders of 40A. If I place a zener diode, shouldn't it need to flow 40A for brief time?
350V and 40A (peak) zener diode, can I find them?
 
I think you need a re-design. Dump regulators need to be phase angle controlled, 3 phase ones are difficult to build as you need to phase control 3 switching devices. That is a common system as seen in just about all motorcycle 3 phase regulators.

If you just short out a rectifier output with PWM it is going to always be shorting and releasing the supply inductor at peak current making massive spikes.
 
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