Re: Gatedrive waveforms

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dan Strother by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dstroth-at-hotmail-dot-com>

You will not be able to accurately assess the gate drive waveforms until 
the MOSFETs are installed. The MOSFETs' gate capacitance is the primary 
cause of such undesirable effects.


Dan Strother





>Original poster: "Finn Hammer by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><f-h-at-c.dk>
>
>Dan, all:
>
>Thankyou, Dan, for this little tutorial, you are helping a lot in
>extending the experience of SSTC`s to the part of this community, that
>don`t have electronic experience, like myself.
>
>You write, that when testing the gate drive signal, overshoot and slight
>ringing is okay. I have recorded these waveforms from my board, this
>being without the FET`s mounted.
>http://home5.inet.tele.dk/f-hammer/gatedrive.jpeg
>
>The pink trace shows both turnons, and one turnoff, the green trace
>shows the turnoff extended in time.
>
>The turnons overshoot to 15.6V, then ring back to 9.4V
>
>The turnoff`s overshoot 5V, then ring 4.2V opposite.
>
>Having litle knowledge of this subject, I would like to ask, if these
>are acceptable values for overshoot and ringing, so that I may proceed,
>or is troubleshooting indicated.
>
>I should be getting 125 IRFP460A`s this week, and am looking forward to
>testing the rest of the features.
>
>Cheers, Finn Hammer