| Electronics > Projects, Designs, and Technical Stuff |
| Current pulse generator project |
| << < (4/4) |
| David Hess:
--- Quote from: MasterTech on December 18, 2018, 05:55:36 pm --- --- Quote from: David Hess on December 17, 2018, 08:25:46 pm ---The driver drives the MOSFET instead. The IGBT gate is then tied to a low impedance positive bias supply high enough to fully turn it on. --- End quote --- Got it, will try it in a future version. --- End quote --- I should have mentioned that the only reason this works is that IGBTs and MOSFETs have the same gate drive requirements. A high current low voltage power MOSFET driving the emitter of a bipolar transistor has the advantages of both devices and is sometimes used where either alone would be either prohibitively expensive or not high enough performance. I have never tried it with a IGBT replacing the bipolar transistor but if I ever have an excuse to, I will. |
| daqq:
--- Quote ---Eventually this worked very well, I added another 3.3 ohms in series (3x10ohm paralleled) with the 2.2ohm and the rise time nearly halved. This limits the current pulse of this setup to about 200A, but with this I can test current probes of >2MHz bandwidth. I shortened the pulse to 5us for the sake of the resistors well-being. --- End quote --- Yeah, you are getting to the limits imposed by your transistor, but you still have some space there. You can probably further reduce the inductance of the setup by reorganizing things a bit (make the loop as small as possible) and adding a smaller capacitor parallel to the setup (the big one is on somewhat longer leads). I think to go any faster, you'd have to go into MOSFET territory. |
| PartialDischarge:
--- Quote from: daqq on December 19, 2018, 06:15:02 am ---Yeah, you are getting to the limits imposed by your transistor, but you still have some space there. You can probably further reduce the inductance of the setup by reorganizing things a bit (make the loop as small as possible) and adding a smaller capacitor parallel to the setup (the big one is on somewhat longer leads). I think to go any faster, you'd have to go into MOSFET territory. --- End quote --- I need a small loop to fit in the A6303 head, anyway I'm happy with the results. My aim was a 1-5MHz current pulse at at least 100A, and I plan to increase currents in future setups not necessarily (decrease) rise times. The fall time of the 100A pulse gives me 4MHz. I have another setup with 1800V 2000uF polypropylene busbar caps that are shorted with a thyristor. I used that to create high temperature arcs using thin wires. Never got to study the currents in that setup, I did estimate currents in excess of 10kA based on the voltage discharge profile (I may need a coaxial shunt) but I can tell that the cables did shake after each shot. |
| Navigation |
| Message Index |
| Previous page |