motor stall current vs Victor ratings

[Al Skierkiewicz]

DA,
Maximum rated current for a Victor was published a few years ago but can be derived from the current specifications for the MOSFETs used. Keep in mind that each FET is in parallel with two others for current sharing but that there is derating due to lack of heatsink. The FETs have a very low "on" resistance and so very little power is dissipated within the device which keeps internal heating to a minimum. However, there are other factors...usually at maximum current, a) the speed controller is no longer using a PWM output, it is at full "on", b) the motor is at or near stall, c) the motor may be back driven by a pushing robot, d) bad electrical connections at the Victor will raise it's temperature due to heating of the contact area, e) the fans become inefficient due to the lower battery voltage. Keep in mind that about 90% of all speed controller failures are due to foreign and conductive material inside the controller. The remaining failures are a result of incorrect wiring, over heating, repeated high current due to stalled motors or rapid direction changes or defective mechanical systems.
As pointed out, many teams design for at least 6 ft/sec but speeds from 8-12 ft/sec are acceptable. Higher speed designs will result in mechanical systems that will easily stall and draw excessive currents when starting or accelerating.