Motor terminal snubbing circuit
A snubber circuit to mitigate voltage overshoot in a power train for driving a motor, the snubber circuit configured to be connected to the motor terminal between a transmission line from a power supply and converter and a motor. The snubber circuit includes a rectifier, a capacitor connected across an output of the rectifier and a load connected across the capacitor. The capacitor is rated to charge to a predetermined link voltage and wherein an input voltage to the rectifier that exceeds the link voltage causes the voltage at the motor terminal to clamp to the link voltage and for excess energy from the input voltage to be stored in the link capacitor and dissipated by the load.
1 . A snubber circuit to mitigate voltage overshoot in a power train for driving a motor, the power train comprising a power supply, a power converter connected to the power supply, and one or more long transmissions lines from the power converter to the motor that connect the output of the power supply to the motor, the snubber circuit configured to be connected to a terminal of the motor between the one or more long transmission lines and the motor, the snubber circuit comprising:
a rectifier;
a link capacitor connected across an output of the rectifier; and
a load connected across the capacitor;
wherein the capacitor is rated to charge to a predetermined link voltage and wherein only when an input voltage to the rectifier exceeds the link voltage the snubber circuit is activated by an output of the power converter to cause the rectifier to clamp the voltage at the motor terminal to the link voltage and for excess energy from the input voltage to be stored in the link capacitor and dissipated by the load.
2 . A snubber circuit according to claim 1 , further comprising a resistor in series with the capacitor connected across the rectifier output.
3 . A snubber circuit according to claim 1 , wherein the rectifier is a 6-pulse rectifier.
4 . A snubber circuit according to claim 1 , wherein the load is a passive load.
5 . A snubber circuit according to claim 1 , wherein the load is an active load.
6 . A power train for driving a motor, the power train comprising:
a snubber circuit as claimed in claim 1 ;
the power supply;
the power converter connected to drive the motor via the one or more long transmission lines;
wherein the snubber circuit is connected between the one or more long transmission lines and a terminal of the motor.
7 . A power train according to claim 6 , wherein the converter is a PWM converter.