nino500 wrote:I'd like to have a reliable failsafe in case of runaway/welded contactor situation. Would it be possible to have a mechanically seperated emergency contactor? Perhaps pulled open by hitting the clutch pedal (no actual clutch fitted so this would be its only use)
I have seen circuit breakers used with a remote panic button/lever inside the vehicle, operated by a cable. The trick is finding a suitable circuit breaker!
nino500 wrote:Another question about contactors: We all know that series motors can run several times over their rated voltage. What about contactor coils? If a system voltage was upped from 48 to 72 volts would the 48 volt contactors handle it or would this be suicide?
Cheers, Nino.
Motor ratings tend to reflect what the manufacturer was asked to supply rather than the capability of the motor. This does
not apply to fuses, circuit breakers, wiring, switches, contactors etc. You must not exceed the manufactures ratings.
For a contactor there will be 2 voltage ratings, one for the coil that operates the contactor and the maximum voltage the contactor can break across the contacts. Make sure you are looking at the DC ratings, they will be
much lower than the AC ratings. Since the coil and contacts are isolated from each other you can increase pack voltage to the maximum ratings of the contactor as long as you don't change the voltage to the coil. The coil voltage must match the voltage you are going to operate the coil with, normally 12 volts, but check this as it can be different for some controllers, My Kelly controller uses 24 volts so I have a seperate DC-DC convertor to operate the contactor and control side of the controller. I can then use any traction pack from 24v to 72v with this motor and controller without having to change anything.