Originally Posted by epyon
...What contactors are you using ?
We put the main contactors inside the controller, greatly simplifying that side of the EV wiring. All Ron needs to provide is the mandatory emergency disconnect (often called the "oh schiesse!" bar).
If you were asking about the contactors needed to do series/parallel shifting of the motors, there aren't any. Or, at least, there better not be. I don't really think S/P shifting is all that great at 1000A, but at 3000A it turns into an exercise in futility. This is because it takes (3) normally open switches (ie - contactors) to shift the motors from being wired in series to parallel. The series connection switch needs to be rated for the maximum motor current - or 3000A in this case - while the two parallel connection switches need to be rated for at least half the maximum motor current, say 1600A, as there will inevitably be a slight imbalance in total resistance for the wiring of each motor.
If the popular Albright SW200 contactor is to be used for all of the S/P switches then it would take *15* of them for the series switch and *8* of them for each parallel switch. A total of *31* contactors. That's just nuts.
To make matters even worse, a quality under/overdrive can shift gears faster than you can electrically rewire the motors. The reason is because before you shift from series to parallel you have to cut throttle to zero and then wait for motor current to do the same. The inductance of motors is high and their resistance is very low so their electrical time constant (L/R) can exceed 0.1 second, and the rule of thumb is that current through an inductor will decay to zero after 5 time constants (e.g. - 0.5 second). If you try to S/P shift before current has dropped to zero then a huge arc will jump across the contactors in defiance. You'll definitely damage the contactors and you might just hurt the controller, too, since this voltage might exceed what the semiconductors inside can handle.
So we don't much like S/P shifting at Evnetics, and judging by the amount of time that I see racers waste on getting it to work properly, I'd say we're on the right side of that argument.