Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

operating condition in an electric motor in which the torque developed between the stator and rotor coils opposes the direction of rotation of the rotor. Typical braking methods in DC machines include "plugging" in which the polarity of either the field or the armature coil, but not both, is reversed while the rotor is turning, "dynamic braking" in which generator action in the armature is used to dissipate rotor energy through a braking resistor, and "regenerative braking" in which generator action in the rotor is used to dissipate rotor energy by returning electric power to the power source as the rotor slows. Typical braking methods in AC machines include switching of the phase sequence of the supply voltage, dynamic braking through the armature coils, and varying the frequency of the AC supply voltage.
See phase sequence
braking resistor
resistive elements which can be switched into the electrical system to create additional load in the event of a transient disturbance, thus limiting the generator rotor acceleration such that the system can more readily return to synchronism.
dynamic braking
since AC motors do not have separate field excitation, dynamic braking is accomplished by continuing to excite the motor from the drive. This causes a generative current to the drives DC intermediate bus circuit. The dynamic brake resistors are then placed across the DC bus to dissipate the power returned. The brake resistor is usually switched by a transistor or other power switch controlled by the drive.