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 rapid deceleration, enough excess energy can be transferred to shut down the drive or damage the power supply.

Shunt regulators work by 'clamping' the power supply voltage to a set level. If the power supply voltage exceeds the set limit, the shunt regulator will 'bleed off' excess 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.

When are SRST's required?

Excess regeneration energy is produced when:

• A drive brings a large load to a stop
• Vertical deceleration against the force of gravity
• Under rapid deceleration (including smaller loads)

If the excess energy is enough to raise the power supply voltage above the rating of the amplifier, then a shunt regulator is suggested.

Setup

Attach the leads across the DC power supply.

Power Supplies

DC Power Supplies