Electrical machine braking methods are used to decelerate or stop the motion of electric machines, such as motors and generators. These methods vary depending on the type of electrical machine and the application. Here are some common types of electrical machine braking methods:
Dynamic Braking: In dynamic braking, the electrical machine operates as a generator and converts the mechanical energy of the rotating shaft into electrical energy. This electrical energy is dissipated as heat through resistors or other dissipative elements. Dynamic braking is effective for rapidly decelerating the machine, and it is commonly used in applications where the load has a higher inertia than the motor can handle.
Regenerative Braking: Regenerative braking is employed in electric machines equipped with power electronic converters, such as electric vehicles and some industrial drives. When the machine needs to decelerate, the power electronic converter reverses the direction of current flow in the windings, turning the motor into a generator. The generated electrical energy is then fed back into the power supply system or stored in a battery for reuse. This method is more efficient as it recovers some of the braking energy and reduces energy consumption.
Plugging (Reverse Braking): Plugging, also known as reverse braking, involves reversing the direction of the current in the machine's windings. This rapidly decelerates the motor by producing a reverse torque. Plugging is often used in applications where rapid stopping is required, but it can be more severe on the motor and electrical system due to the high currents generated during the braking process.
DC Injection Braking: This method is commonly used with induction motors. It involves injecting a controlled DC current into the stator windings, which creates a stationary magnetic field. The interaction between the rotating magnetic field of the rotor and the stationary magnetic field of the stator creates a braking torque. DC injection braking is relatively simple and provides good control over braking torque.
AC Injection Braking: AC injection braking is similar to DC injection braking but involves injecting AC current into the stator windings. The interaction between the injected AC current and the rotating magnetic field generates a braking torque. AC injection braking is less commonly used than DC injection braking but can be more efficient in certain applications.
Mechanical Braking: While not strictly an electrical braking method, mechanical braking mechanisms, such as friction brakes or eddy current brakes, can be combined with electrical machines for additional braking power. Mechanical brakes can be used as primary or backup systems in conjunction with electrical braking methods.
The choice of the appropriate braking method depends on the specific requirements of the application, the type of electrical machine used, and the desired control and efficiency characteristics.