DC injection brakes slow down AC electric motors. Dynamic braking lowers the wear of friction-based braking components, and can regenerate energy, saving on operating costs.
After disconnecting the AC voltage supplied to an AC motor, DC voltage is injected into the windings of the motor, providing a braking force to the rotor. This creates a stationary magnetic field that applies a static torque to the rotor, which slows and eventually stops. This static torque holds it in position until the DC voltage is either changed or removed. The higher the DC voltage, the stronger the braking force and holding power.
Dynamic brakes are used to assist AC drives in periodically decelerating loads without tripping overvoltage sensors and fuses. This system consists of at least one transistor and one resistor and is sized for rated motor horsepower. A braking transistor may be included in the standard drive. These resistors are sized for a 10% duty cycle and will provide approximately 150% braking torque.
Dynamic braking can also use the electric traction motors of a vehicle as a generator when slowing. Rheostatic braking occurs when the generated electrical power is dissipated as heat in brake grid resistors. Regenerative braking refers to systems in which this power is returned to the supply line.
During dynamic braking, the motors become generators and are connected to "braking grids". These grids contain large resistors that limit the current flow and dissipate the
Hoffmeyer offers both electronic and mechanical motor brakes, including a selection of AC motor brakes with dynamic braking capabilities.
With over 90 years of experience, Hoffmeyer provides you with a wealth of expertise to find the motor brake solutions you need. Contact one of our customer service specialists today; they will help you find the right equipment, accessories, and adapters to make your conveyor belt systems start and stop exactly the way you require. Hoffmeyer can even provide specially designed solutions if you have unique needs or unconventional applications.
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