IGBT switching faster than the gate signal

[Phoenix6478]

Hello everybody  ,
I am new here.
I am building a DRSSTC using IGBT Bricks and everything is working fine but i have a question: My rise/falltimes are always very slow at the gates of the IGBT's (over 1uS), but if i measure the output of the H-Bridge while the primary circuit is connected, i get super fast switching times (120nS/80nS).
Why are the Bricks switching faster than the input gate signal? I know that this is a good thing because then i get less losses. Is the higher primary current somehow supporting the switching process?

Greetings,
Phoenix

[Whales]

(Not familiar with IGBTs, assuming they don't have any fancy input latching)

The IGBTs are acting as amplifiers during the short switching period.  A small amount of voltage/current rise on the input creates a large amount at the output.

The result is the output looks like it's changing faster than the input.

[Phoenix6478]

Thank you for your fast response
I am using SKM200GB128D Bricks from Semikron. The whole setup is running at 75kHz via Feedback and soft switching. So i can get away with slow rising times at the gates and without to much losses?

[danadak]

This might help -





http://www.ti.com/lit/ml/slua618/slua618.pdf

[filssavi]

The raise and fall time of the gate pulse are not reallylinked to the switching time of the IGBT, apart from the obvious maximum frequency limitations  (you have to fit a full raise and fall time in a period)

once past the treshold voltage the switching speed depends on how much current you can pump into the gate to charge it's capacitance up to the desired voltage

another thing that you have to keep in mind is that the switching times you find in the datasheet are specified at Ic=150A Vce=600V 7ohm gate resistance and +-15V Vgs

and since I doubt you are switching 90 kW (I guess you are switching high-ish voltage at a lower current) the switching times at lower operating conditions will go down