Transient over voltage problems are quickly solved using shunt regulators that clamp regeneration voltage to safe levels. These simple devices can increase system reliability by stabilizing voltage fluctuations and eliminate over-voltage shutdowns.

The purpose of a shunt regulator is to 'burn off' excess regeneration energy that is produced when a drive brings a large load to a stop. Mechanical braking systems use friction to stop a load and convert kinetic energy into heat. Servo drives on the other hand are very efficient power converters - typically over 98%! They convert electrical energy from the motor to the power supply just as efficiently as when they convert energy from the power supply to the motor. During a rapid deceleration or the deceleration of a large load, enough excess energy can be transferred to shut down the drive or damage the power supply.

A shunt regulator 'clamps' the power supply voltage to a set level and prevents unexpected shutdown or damage. It monitors the power supply voltage and if the voltage exceeds the set limit, the shunt regulator 'bleeds off' the extra voltage through a power resistor. The shunt regulator is only active when the voltage exceeds the set level; otherwise, no current passes through the power resistor. The shunt regulator automatically turns the power resistor on and off as necessary to regulate the voltage, sometimes up to several hundred Hertz.