Cut the red wire?

[bulletbug]

I'm using a Tesla small front drive unit in a Bug. I'd like to have 2 safety features incorporated into what I'm building.

1. An OHHH Crap button - same as you'd have on a cnc machine or 3d printer to stop the system manually. I'm it's a simple "normally close" red button on the ignition wire going to the inverter. What is the behavior of the inverter if it is turned off while the car is moving at freeway speeds? Would it be better to put the Normally closed switch on another line?



2. Inertia switch (crash switch used to cutoff fuel pumps in ICE cars) in case of crash, would it make sense to just cut off the same "ignition" line to the inverter? Are there additional items that should be tripped in case of an accident?

Thanks for anyone's input. If you have any example of implementing this sort of thing, I'm all ears.

David

[Isaac96]

Hi,
1. There is the EMCYSTOP input for such applications.
If you shut off the 12v power to the inverter, the contactors will open even if the motor is spinning -- and with the Tesla units I believe that will blow up the inverter. EMCYSTOP will just shut off PWM, saving your power stage from spontaneous unscheduled disassembly.

2. This is a little different; if an inertia switch trips, chances are you hit something. And if you hit something you probably aren't moving very much. Then it would probably be safe to disconnect HV - cut the ignition for that.

-Isaac

[arber333]

Hi,
1. There is the EMCYSTOP input for such applications.
If you shut off the 12v power to the inverter, the contactors will open even if the motor is spinning -- and with the Tesla units I believe that will blow up the inverter. EMCYSTOP will just shut off PWM, saving your power stage from spontaneous unscheduled disassembly.

2. This is a little different; if an inertia switch trips, chances are you hit something. And if you hit something you probably aren't moving very much. Then it would probably be safe to disconnect HV - cut the ignition for that.

-Isaac

1. EMGCY button with ACIM motor should stop PWM and trip main contactor, that is OK. BUT with PMSM motors you should leave contactor ON because you may trip this button accidentaly on the road while motor is in field weakening. Then resulting EMF voltage could damage IGBTs if path to battery is cut.

2. Yes i would advise to use inertia switch with a latching relay in a failsafe fashion, cutting its GND line so contactor would trip if you hit something or you overturn the car.

[johu]

Thing is... Tesla boards don't have the EMCYSTOP input. You could simply turn off the direction input (forward, normally) that will also shut down PWM.
I've tried turning ignition off in Polo, that also works. The car coasts after that and nothing blew up.

[P.S.Mangelsdorf]

I'm using a Tesla small front drive unit in a Bug. I'd like to have 2 safety features incorporated into what I'm building.

1. An OHHH Crap button - same as you'd have on a cnc machine or 3d printer to stop the system manually. I'm it's a simple "normally close" red button on the ignition wire going to the inverter. What is the behavior of the inverter if it is turned off while the car is moving at freeway speeds? Would it be better to put the Normally closed switch on another line?



2. Inertia switch (crash switch used to cutoff fuel pumps in ICE cars) in case of crash, would it make sense to just cut off the same "ignition" line to the inverter? Are there additional items that should be tripped in case of an accident?

Thanks for anyone's input. If you have any example of implementing this sort of thing, I'm all ears.

David

If its just for street driving, everyone else's answers are going to be more helpful.

However, if you want to drag race the car (at an NHRA track), I'd recommend using a completely separate emergency contactor on both the 12V and HV for the entire car. NHRA and NEDRA rules call for both the driver and someone outside the car to be able to completely disable the car with a single switch. I've run the driver (dash mounted) and rear kill switches in series to a 12V and HV contactor in parallel on a previous build. On my new one, the HV contactor will be turned on by the 12V contactor, the dash and rear kill switches will still be in series.