DC Injection Braking Demo
DC injection braking is a method of slowing down a motor with electricity and no mechanical brake. It is done by disconnecting AC power from the stator windings, and connecting DC while the motor is spinning. This creates a stable magnetic field on the stator in which the rotor continues to spin. The magnetic field causes a voltage to be created (and therefore a current to flow) on the rotor because you have a conductor (the rotor) spinning in a stationary magnetic field (think e=Blv). By Lenz’s Law, this induced current creates a magnetic field which creates a counter-torque to the direction of rotation which has the effect of slowing down the rotor. The kinetic energy of the rotor is then burned up as heat on the rotor due to the eddy currents circulating in the rotor (again, by e=Blv).
Watch the video for a demonstration: