Brake chopper


A brake chopper is used to monitor the DC link voltage in a frequency inverter. This monitoring is necessary because power surges can occur in the intermediate circuit. They arise when the motor is broken. An element called the brake resistor is connected to brake chopper, which converts the excess energy in the DC link into thermal energy. Like an electronic switch the chopper switches the resistance before the DC link voltage reaches a dangerous level for the components. When the intermediate circuit voltage decreases again and becomes lower than the turn-on voltage, but greater than the line voltage, the chopper switches the brake resistor off again. The process is repeated as soon as the voltage rises again.

Operating mode of a brake chopper

If you consider a drive-system, it comes with a velocity “v”, so it has a kinetic energy. If the system is slowed down, the excess energy flows in the form of regenerative power from the amplifier back to the DC link. If this voltage exceeds a threshold voltage, the chopper is switched electronically. The excess energy is then converted by the connected brake resistor almost entirely into thermal energy. The limiting factor is the brake resistor, because within it a large amount of energy is converted into heat. The losses in brake chopper are not relevant.

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