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| PartialDischarge:
I've been working on a current pulser, short pulses (adjustable 5-100us) in the 100s of Ampere range (adjustable). This one I made should get to 600-700A. I've been researching thyratrons for this reason but this one is IGBT based. The system is simple, a high voltage adjustable 0-1000V DC-DC converter charges a capacitor (42uF) that is discharged through a low inductance power resistor (Vishay RPS250) by means of a IGBT (CM300DC). The pulse is a one shot generated by a 555 an applied to a IGBT driver. I used thin paralleled copper bars to make the joints and kept distances small. The heatsink acts as ground plane. I got a respectable 210ns rise time. This is the system: And some measurements with the Tek A6303 and AM503B amplifier. I didn't go over 100A just yet, since I need something else to go beyond that. 50A pulse, 10us. 50A pulse rise time. 100A pulse and the VGE of the IGBT 100A rise time. |
| daqq:
Nice setup! Minor observations/tips: It's better to have the gate drive twisted together, this lowers the loop area, lowering the gate series inductance. A bit lower main circuit inductance could be achieved by connecting E2 from the other side. A steeper edge could possibly be achieved by using a higher resistance (thus lowering the L/R constant) with higher voltage. At these speeds you could be dealing with a limitation of the transistor. If you want some (other) resistors that can take some serious pulsed abuse, see: http://www.hvrint.com/rtrlseries.htm https://www.hvproducts.de/en/hv-passive-components/bulk-ceramic-non-inductive-resistors/ If you need this for some really serious applications (since you've been looking into thyratrons), you could take a look at the goodies Behlke has: http://www.behlke.com/productlines.htm Don't forget to add a snubber if you'll be connecting loads that add inductance to the system. |
| Wolfgang:
Hi, nice pulser ! Some comments though: - IIRC High power IGBTs as well as MOSFETs have a dI/dt rating. If you go to still higher currents this rating could be exceeded. - The base circuit must be free of resonances (including the hefty and nonlinear IGBT capacitance). A voltage spike caused by a resonance could kill the gates. Damping is a good idea. Use twisted wire and a termination resistance (e.g., 120Ohms). - Turn-off time of IGBTs can be long. When they need to be fast, you have to "suck out" current from the gate. Your IGBT driver probably does that. Some years ago I tried to build a can crusher using semiconductors. No survivers so far. The weapon of choice for games like that is probably an IXYS pulse power thyristor. These bastards withstand up to 90kA and a few kV. But the price is astronomic. Have fun Wolfgang |
| Insatman:
I had lots of experience designing low impedance drivers. What we did was use a step-down transformer so you can switch at higher voltages and lower dI/dt. Then step-down the drive impedance with a pulse transformer. With proper design you get better rise/fall times. Of course pulse length is limited by the magnetics. |
| David Hess:
What about grounding the gate of the IGBT and driving the emitter with the drain of a power MOSFET which then only has to sustain low voltages? |
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