The reason for the 40 A breakers is to delay the onset of "Puff". When those engines start (with a Drive-it-like-you-stole-it driver), or when some Idiot tries to push the end wall and your wheels have absolute traction on the carpet, the motors aren't turning very fast, the back emf they generate is zero, and they draw the "Stalled" or "Locked rotor" current in the specifications. For how long depends on the fuse. One sheet said that when one of these motors (I forget which) was stalled, it acted like a .0999 ohm resistor, or, using Georg Simon's wisdom, it draws blessed 120 A ! ! !
Once they are moving the 'bot somewhere, and their back emf approaches the applied voltage, the current drawn becomes a lot less (like "20 A"). This is the "under normal driving conditions" state, where the fuses don't blow anyway.
And, when the load is primarily braking (sudden shift to speed = 0 on a 'bot going all ahead full), the current in the Victors is in the loop between the Victor and its motor. As stated above, this circulating current can be very high, and it doesn't flow through the breakers.
These are not TOYs, but they get the respect Rodney Dangerfield gets ! Pfui !
What makes a man is not the mistakes, but the actions that follow.
Andy B. - Andy Baker [more] 
05-02-2003, 10:05
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