On 6/20/2014 8:50 PM, Harold Zimmerman-Clean Power Supply wrote:
They began using the permanent magnet motors on the E12JA which was probably late '72 or early '73. Both the wound field version and the permanent magnet version used a centrifugal switch which was meant to keep 2A contactor form pulling in until the motor reached a certain RPM, preventing "Jack-Rabbit starts"
I would assume the PM motor would need the armature switching control to reverse. Fair enough, and on thinking I see why the clutch is needed: On an E20 you have to step through three speeds to get to full power, so you can't really pop wheelies. On the E15 there are the capacitors to do brief timing intervals between the speeds since there are only two of them before full power. But an E12 has only two intervals, so you would want the clutch to limit the power.
Nicely done by GM....