Method and apparatus to dissipate recovered energy from a mechanical load within a connected motor during braking

A method of dissipating recovered energy from a mechanical load within a connected motor during braking, the method comprising:

• storing power received from an AC power line in a DC power storage device;
• inverting the stored DC power to a multi-phase power and providing the multi-phase power to the motor;
• calculating an (ID) current corresponding to a rotor angle of the motor from values of currents of the multi-phase power being provided to the motor, the ID current producing only motor energy losses and IQ current being directly proportional to the motor's shaft torque;
• calculating an ID target current based on monitoring the voltage across the DC power storage device (Vbus);
• and
• adding ID to the currents of the multi-phase power based on the monitored value of Vbus.

An energy dissipation control circuit to dissipate energy stored in a DC storage device within a motor drive circuit, comprising:

• a first comparator to continuously monitor and compare a DC storage device voltage (Vbus) value to a voltage maximum limit (Vlim) of the DC storage device;
• a second comparator to continuously monitor and compare the DC storage device voltage Vbus value to a predetermined voltage value below the Vlim;
• and
• a controller to provide a target output current dissipation value to the motor drive circuit to decrease the Vbus value based on the monitored Vbus value, the target output current dissipation value being varied depending on the monitored Vbus value.