what is breaking resistor
Breaking resistor is a high wattage resistor used to control speed of motor it is used to stop motor quickly by draining excess voltage and keeping it within safe tolerances.
Application examples
Cranes: When a crane is being used to lower a heavy load it has to contend with surplus potential energy, which could cause the motor to run away in an uncontrolled manner, thus creating a safety hazard. A braking resistor can be used to prevent this from happening.
Elevators & lifts: When elevators and lifts are descending and carrying people there is excess potential energy which tends to drive the lift motor in reverse, thus making it operate like an alternator. A braking resistor can be used to dissipate the unwanted electrical energy. There are some purpose-built units for this duty, engineered for roomless lifts and for fitting inside the framework of an escalator. These resistors have special EMC connection boxes which are required in public buildings and can provide protection against damp and dust. Importantly, this type of resistor does not require an additional housing, thus they can be used in confined spaces and usually cost less than enclosed resistors.
Electric locomotives: Dynamic braking resistors are often used in conjunction with air-brakes in electrical locomotives to reduce the amount of wear on mechanical components. When it is switched into circuit the braking resistor causes the current to flow in the opposite direction to when the locomotive is motoring. Therefore, the motor exerts a torque that opposes the forward motion.
Wind turbines: Braking of a wind turbine can be achieved by “dumping” energy from the generator into a braking resistor. This technique is useful if the kinetic load on the generator is suddenly reduced or is too small to keep the turbine speed within its allowed limit. Also, in faster winds, it is possible to introduce cyclical braking which causes the turbine blades to slow down. This increases the stalling effect, thus reducing the efficiency of the blades. In this way the turbine’s rotation can be kept at a safe speed.
