# Mov



## Anaerin (Feb 4, 2009)

Unless I'm missing something, isn't Motor- AKA Pack ground?

If you're suggesting a short from Motor+ to GND under high current, erm, you'll probably blow your batteries.

Most wiring designs have (or damned well should have) a fuse rated for just below (or at) the current limit of the controller in use, so if you have a 500A controller, you'll have a 500A (Or 480A-520A for a little safe room either way if you find you're blowing fuses too much) fuse in the circuit, probably on Battery+. This is there to both protect the controller from runaway events, but also to prevent "Plasma Events" from short circuits, and to help mitigate potential contactor welding issues.

Reading up on Varistors, Wikipedia notes that "A varistor provides no equipment protection from inrush current surges (during equipment startup), from overcurrent (created by a short circuit), or from voltage sags (also known as a brownout)". Given that it seems Varistors are meant for supressing Voltage spikes, rather than Amperage spikes, and there is little opportunity for excessive voltage to appear in an EV (Your voltage is limited by your pack), there seems little need for one of these.


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