Patchem, Eric EM2 wrote: > How is an AC induction motor (in the case of AC drive) used for > regenenerative braking? I understand how the motor works, but I > cannot see how it would work as a generator. I know the inverter > plays a major role in this, but I cannot see how an induction motor > with no field connections, can produce an output.
Any induction motor acts as a generator if you connect it to an AC power source and turn it faster than its synchronous speed. For example, plug any ordinary induction motor into the 60 Hz AC line. Suppose it runs at 1725 rpm. Turn it at 1800 rpm (synchronous speed) and the current it draws drops to zero. Turn it FASTER than that, like 1875 rpm, and it GENERATES the same amount of power it would have used as a motor, pushing the power back into the AC line. The field of an induction motor is the rotating part (the rotor). The field is powered by transformer action from the stator. All you need to power the field is a source of AC applied to those stator coils. The AC line (or inverter in the case of an EV) is supplying the AC to excite the field. Since field power is only a tiny fraction of total motor power, it can generate far more power than the field consumes. -- Lee A. Hart Ring the bells that still can ring 814 8th Ave. N. Forget your perfect offering Sartell, MN 56377 USA There is a crack in everything leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
