VFDs often contain brake transistors which switch on and off to allow excess energy to be shunted across a braking resistor. However, if the brake transistor fails and goes undetected the resistor could see an abnormal amount of current which could lead to failure or even a fire.
KEB's external bake transistor monitor can be added to VFDs in the field. It monitors the status and health of the Brake transistor connected to the AC drive. If the monitor detects a short circuit, it safety disengages the Brake resistor.