Patent ID: 7944157

Claim:
A motor drive control system comprising: communication media including at least one network line; a plurality of motor drives, each motor drive comprising: (a) a motor control circuit for controlling an electric motor; (b) a media access control unit (MACU) having: (i) a first communication module and a second communication module, each having a transmitter and a receiver joined to the communication media, (ii) a set of four routing switches joining the first and the second communication modules to connect the motor drives in an independent primary ring and a secondary ring communicating data for controlling the motor drives wherein a first routing switch joins the transmitter of the first communication module with the receiver of the second communication module, a second muting switch joins the receiver of the first communication module with the transmitter of the second communication module, a third routing switch shunts the transmitter and receiver of the first communication module and a fourth routing switch shunts the transmitter and receiver of the second communication module and wherein at least one of the primary ring and secondary ring include a segment joining a transmitter and receiver of one communication module.