If a motor is in an overhauling condition – that’s, the load is moving much faster than the designated motor speed – the motor functions as a generator and also has electric power from physical energy. This particular power energy, nonetheless, needs someplace to go, and also the most typical method of coping with the release of its is through compelling braking.
Exactly how compelling braking works
With compelling braking, the power power produced during stopping is released as heat by way of a a voltage regulated resistor and also transistor. You will find 2 types of a powerful braking circuit: a “chopper” & a “dynamic brake.” The compelling brake circuit includes the switching unit (an insulated gate bipolar transistor, or maybe IGBT), the control circuit, as well as the resistor.
A chopper, on the opposite hand, only comes with the regulatory circuit plus turning unit, with the resistors getting individual components. This enables the dynamic braking resistors to be properly sized and mounted remotely, that may be vital, since the resistors produce a considerable level of heat. The blend of changing device and control circuit is frequently called the “chopper module,” while the resistor is called a “dynamic brake resistor.” Dynamic brakes are generally rated for duty cycles in the twenty % range, along with choppers are usually utilized in heavier duty applications.
You will find 2 control types for compelling braking: hysteresis control and PWM (pulse width modulation) control. With hysteresis control, the control circuit keeps an eye on the DC bus voltage level and turns the transistor on once the voltage reaches a predetermined level, to stay away from an overvoltage fault in the drive. When present is streaming towards the resistor, the power is converted into heat, that causes the DC voltage to decrease. As the voltage drops to a preset “low” level, the transistor is switched off.
Where hysteresis management turns on the transistor and foliage it on until the voltage drops to a predetermined level, PWM control spins the resistor on and off based on the degree of the DC bus voltage. Generally, hysteresis & PWM control techniques are equivalent in function, but PWM control is chosen for uses with the same DC bus since it can help stay away from a situation in which one drive does a disproportionate share of the powerful braking work.
Dynamic braking or even regeneration?
Dynamic braking is needed when power has to be dissipated periodically, and also regeneration is frequently preferred once the engine is often acting as a generator. By an application standpoint, overhauling loads (a problem in which the load is moving much faster than the designated motor speed), like cranes and conveyors, produce energy being created constantly and make healing and reuse much more cost effective. But applications in which the deceleration speed varies, like fans, are ideal for compelling braking. While regeneration lowers energy consumption, dynamic braking decreases wear on braking components which depend on friction. And while electricity is squandered as heat in compelling braking, the initial cost of its is considerably less than that of regenerative drives.