Thyristor SCR gate trigger
It does not say that you should apply 30V to the gate- it says the drive circuit should produce at least 30V with the gate disconnected. A current source with 30V compliance would satisfy that, and a resistor from a voltage source of 30V would as well. If you do not exceed the recommended drive current, the gate voltage will not exceed the maximum.
Applying excessive gate current using the back porch will increase gate dissipation, so it is not recommended. More than 100 microseconds at 30W exceeds the maximum. If you are supplying 2A Igm and the gate voltage rises to 15V then the dissipation is 30W.
Some kind of pulse shaping network can be used with a driver to create these waveforms, perhaps through a pulse transformer.
[ Summary: the voltage across R2 needs to be much larger than the Inductive Kick/Bounce.]
How are you managing inductance?
If high dI/dT currents flow in the Ground wiring between Gate Driver and Cathode, the SCR may become confused and start to turn off before all the regions are able to turn on.
Provide us a diagram/photo showing that the high currents will NOT flow between Gate Driver and the Cathode.
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If the gate driver provides a CURRENT, and the ground_bounce is << than the voltage providing that current, you should be OK.
Example: the math for inductive bounce/kick/spikes is
- V_inductor = L * dI/dT
and if your optocoupler connects to one side of the Cathode, and the high current exits the OTHER SIDE of the Cathode, and those two wires are not twisted together, then you should be OK.
However, suppose your current changes 1,000 amps in 1uS (1,000 nanoseconds). Suppose the high_current shares 1cm (0.4") of Ground with the opto-coupler Ground.
The voltage in that shared_ground will be approximately
- V = 10 nanoHenry * 1000 aumps / 1000 nanoSeconds
and
- V = 10 * 1000/1000 = 10 volts
which is a big number, but may be OK if your Gate voltage is 20 or 30 volts.
Just some thoughts. When I was a teenage, I paid good money for the GE Manual on SCRs. Certainly did NO HIGH CURRENT DESIGN with that information.