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Author Topic: High power SCR gate to cathode resistance?  (Read 10821 times)

2E0ILY

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High power SCR gate to cathode resistance?
« on: May 26, 2014, 03:29:18 AM »

I am testing two high power (1000 Amp) SCR's. I read low ohms between gate and cathode in both directions, on both devices, yet they trigger and pass DC under test OK. Is the internal gate / cathode resistor used in high power SCR's a low value? Or is there a chance they are faulty, yet still pass DC current to a small low voltage bulb when the gate is triggered with 2V, and stay passing current with the gate voltage removed? They are actually used in an AC rectification / current control application when in circuit. Thanks.
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Best regards, Chris Wilson.

KA4POL

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RE: High power SCR gate to cathode resistance?
« Reply #1 on: May 26, 2014, 04:23:22 AM »

This voltage measurement is critical as it depends upon the voltage of your meter.
See http://www.galco.com/circuit/SCR.htm
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2E0ILY

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RE: High power SCR gate to cathode resistance?
« Reply #2 on: May 26, 2014, 04:47:22 AM »

This voltage measurement is critical as it depends upon the voltage of your meter.
See http://www.galco.com/circuit/SCR.htm

I am testing with a dual bench power supply to both give power across the SCR anode / cathode / load (bulb) and to trigger the gate.

I appreciate multimeters may not have enough ooomph to trigger /test big SCR's reliably. The resistance reading gate to cathode is done unpowered, by both digital and analogue meters, and is about  10 Ohms, with probes in either direction. Thanks Dieter.
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Best regards, Chris Wilson.
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