Intermittent connection on field only

[Mark McLeod]

I think the Victors will survive.
I actually tested this hypothesis a couple of weeks ago and the 40amp breaker on the circuit will trip before the Victor suffers harm.

The order seems to be:

• Jaguars trip first (most sensitive)
• 40 amp breakers trip second

What this means is that swapping the Jag out for Victor will help in marginal cases, but won't do any good if the problem is more than borderline.
Some gear ratios just need to be recalculated.

[techhelpbb]

Originally Posted by Mark McLeod

I think the Victors will survive.
I actually tested this hypothesis a couple of weeks ago and the 40amp breaker on the circuit will trip before the Victor suffers harm.

The order seems to be:

• Jaguars trip first (most sensitive)
• 40 amp breakers trip second

What this means is that swapping the Jag out for Victor will help in marginal cases, but won't do any good if the problem is more than borderline.
Some gear ratios just need to be recalculated.

I generally agree. The risk is not so much the incidental overload, but the cumulative damage. The auto-reset breakers are not very fast and they often finally open the circuit at currents much higher than their ratings. The Victors are well built and we've been using them for years with very low failure rates but I can see how repeatedly banging on those MOSFETs could result in eventual failure.

[Al Skierkiewicz]

The Victor FETs are rated at around 40 amps each with three in parallel for each leg of the bridge for about 120 amps. This figure is continuous with peaks above that but must be derated as junction temperature goes up. Remember that neither controller has any heatsink for the power devices. The 40 amp circuit breaker can withstand up to 240 amps for short durations but will likely first trip between 100 and 120 amps. The trip point is reduced for each successive trip as the breaker heats up internally. When the breaker trips repeatedly, it buzzes and gets HOT!
The stated trip for the Jag is greater than 90 amps for just under 1 second, with 100 amps stated as the maximum current through the device. Following an over current trip, the Jag will wait about 3.5 seconds before re-enable. While the series resistance for the FET is lower than the one used in the Jag, there are only two per leg.

[techhelpbb]

Originally Posted by Al Skierkiewicz

The trip point is reduced for each successive trip as the breaker heats up internally. When the breaker trips repeatedly, it buzzes and gets HOT!

I just want to add that this means that it's hard to repeatedly overload the Victor's in a short duration of time when the 40A auto-reset breaker is protecting the circuit because the breaker heating causes them to trip at lower and lower currents.

However, each time you let the breaker cool off you run the risk again that the next overload will get a shot at cumulatively damaging the MOSFETs in the Victors because it's back to 240A max and 100A-120A normally.

The time frame between matches can reach that point. Also if you blow cool air on the breakers you increase the risks of this happening.

[Al Skierkiewicz]

Mike,
How did you couple to the wheels from the KOP transmissions? When you reached trip point were you driving straight or turning? Were you using the standard KOP frame with bolts for wheel axles?

All jags were independently powered from the distribution board, fused at 40 amps and wired with 10ga. Power consumption to each circuit should have been the max of 1 motor. Two front motors were Cim's w/ simbox and KOP gears and sprockets with #35 chain and 8" plaction wheels. Rears were the 16000 rpm AM motor coupled to a AM planetary with the simbox and KOP gears and sprockets, 8" omni wheel #35 chain. We realize there is a difference in RPM between front and back, testing under all foreseeable conditions proved it to be an acceptable setup. Our acid test was a %500 game cycle test at accelerated driving speeds. We are going to set the bot up and load test each circuit under varying conditions, this should provide us with some good data.

[Al Skierkiewicz]

Mike,
I am going to bet that the 8" wheels are really the big effector here. Have you calculated your final gear ratio and motor RPM?

[Alan Anderson]

Originally Posted by Al Skierkiewicz

I am going to bet that the 8" wheels are really the big effector here.

Good point. There's a team at Queen City this weekend having Jaguar cutouts on their drive motors, and they have CIMpleBoxes driving 8" wheels.

[Captaindan]

Team fusion did not change a single thing on their bot since the bayou regional, we went to lonestar unbagged the robot and put it on the field it connected and had no problems the entire regional