Brushless alternating current electric servo motor drive

Abstract

AC servo motor drives which allow several AC drives to be connected in parallel and allow for the connection and reconnection of AC servo motors to be accomplished primarily through a central processing unit (CPU). Thus, multiple AC servo motor drives may be ganged under the supervision of the CPU to provide a servo motor with multiple times the current available from a single drive and optionally redundancy in the drives. To provide necessary coordination, the required motor current magnitude and phase (current vector) are broadcast by an axis controller to the drives. This command current vector is broadcast over a high speed serial data bus which allows many simultaneous listeners (the AC servo motor drives). To protect against damage to each drive, each of the three current output terminals is preceded by an output filter. The output filters preceding the terminals permit phase by phase parallel connection of several drives in the service of one servo motor. In the preferred embodiment the drives, CPU, power supply and other major components are modular and plugged into a rack backplane with a double bus structure built therein. The functional modules derive and supply their low voltage power and commands to and from the upper bus structure. However, the new rack backplane configuration includes a high voltage motor drive power bus spaced from the upper bus structure. The new backplane configuration provides a machine controller that eliminates the task of wiring a motor power supply to each AC servo motor drive module.