[SMS]

Hi gang,

Was going down the road, accelerating slightly when the traction fuse blew. Looking into it the positive contactor tests closed, it is a normally open unit. Did a search and could not find another post where a contactor welded while going down the road. Any suggestions on where to look for a cause?

Thanks

 

[cricketo]

I imagine the contactor opened/closed with load being present, so heavy arcing may have welded it shut. A decent controller likely wouldn't recover from a fault in such fashion, but it would be worth to check the fault log on the controller.

 

[remy_martian]

Not enough info.

What's the pack voltage?

What's the current limit on your motor controller?

What's the DC voltage and current rating on the contactor?

You could be running too little hold current into the coil, which increases the contact resistance. I^2 multiplies that R into heat. A weak 12V battery could do same.

What is the contactor switching on and off? The motor's obviously not drawing any current, but what else may be when you switch the contactor?

Are you doing precharge?

 

[SMS]

What's the pack voltage? 44 CALB @3.2V for 140V

What's the current limit on your motor controller? Curtis 1239e at 550A

What's the DC voltage and current rating on the contactor? GV200PA-1 1,000V 4,000A max, 400A continuous

You could be running too little hold current into the coil, which increases the contact resistance. I^2 multiplies that R into heat. A weak 12V battery could do same. Will check the 12V battery

What is the contactor switching on and off? The motor's obviously not drawing any current, but what else may be when you switch the contactor? This contactor is only between the battery and controller. Was driving down the street and accelerating slightly so drawing current.

Are you doing precharge? yes

Thanks a lot for the help

 

[piotrsko]

To weld contacts you generally need an arc or such heavy currents that you over powered something. Intermittent opening under load would be the probable cause.

 

[SMS]

A few seconds before the fuse blew I crossed over some railroad tracks. Assuming that my foot moved up and down on the accelerator and there was some shaking in the car.

For the 400A traction fuse to blow and the contactor to weld shut I would expect a large amount of current to suddenly occur. Have floored the car, not that impressive, so that is not too much current.

Wondering if bouncing the accelerator could cause a spike?
Wondering if the car bouncing caused something to hit, pinch, or rub which created a short? It is a 40 year old VW so somethings are bound to be loose.

Thanks

Scott

 

[cricketo]

Program your controller to limit the current to the amount consistent with other components.