Jaguar Meltdown

[Al Skierkiewicz]

Gary,
The FET used in the Jaguar is a Fairchild FDP8874. Thanks to Scott and the Luminary folks for being so open and providing schematics and descriptions. HEX Power FETs all have a diode that is a fall out of the manufacturing process as I understand. The Fairchild device has a few better specs than the IFI devices in that the On resistance is a little lower, the current rating is a little higher and the gate switching time is a little faster. The diode is speced for a voltage drop at 40 amps so I would guess the diode can handle more than that. With three in parallel, they should handle any current the motor could back feed into them during a motor reversal.
In the one post above about a single FET melting the plastic, I would suspect that the one device had just reached the temperature of the plastic melting point while the others were not far behind. This could easily be a difference in cooling fan flow or contact with the transistor tab. Remember that the IFI Victor did not contain plastic near the transistors so users would have nothing to indicate that the devices were at elevated temperatures without touching them. Luminary is trying to research all the data from the field so it is important to report as much data as you can about the device and it's use at the time of failure. This is a daunting task to sift through what might be actual failure from what might be abuse. Remember that we have had abusive failures every year we have used IFI components. Try as they might, manufacturers can only try to design to minimize abusive failures. There is significant diminishing returns to this equation though. "Make it foolproof and only a fool will use it", as the old saying goes.

[dbeck103]

Being one of the beta teams we had one do exactly what you had happen - it smoked the transistor - Since then we have had two other failures. Luminary Micro has been great about replacing them and trying to determine why they are failing. Ours both failed in drive mode. Please contact Luminary Micro for help if you have failures.