+ How are your modulating the load? PWM or linear?
PWM.
+ How are you dissipating 500 Watts of heat? External to the
+ transistor or internally?
Externally - power resistors. I have one power resistor set up to
absorb the minimum load (about 5 amps). I'll then have a parallel
resistor regulated by the transistor to modulate the current up to a
possible max of about 50 amps. This was something Otmar mentioned to
me a few weeks ago. If I wanted to add even more sophistication to
this project, I could have the LabVIEW setup activate one of several
primary resistors based on the load current selected. This would allow
me to size the transistor such that it would only be responsible for 5
or 10 amps of the load. But I'm not sure I want to add any more
complication and I/O to an already large task! I'm just planning to
have the primary resistor take care of the minimum end of our
operating range and let the transistor and secondary resistor
dissipate the rest. Not as classy... but nothing says our design
project has to be a ready-for-production device! ;)
mason
-~-~- mason s. convey -~-~-
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