Comparison of signal coupling methods for power line communication between a motor and an inverter

It has been shown that the motor cables in variable-speed electric drives are a feasible medium for power line communication (PLC). Communication between an electric motor and an inverter is required because of sensors installed at the motor. These sensors are used in the motor control and in the diagnostics. A PLC signal is coupled through a coupling interface to the motor power cable. Being the only component in the channel that can be affected in the communication system design, the coupling interface thus constitutes an essential part of the system. Different coupling interfaces are already introduced for normal low-voltage networks, but not for inverter-fed networks. This study considers the applied channel characteristics and noise scenario from the viewpoint of communication. Two different coupling interfaces, capacitive and inductive, are developed and analysed by laboratory tests. The developed inductive coupling method makes it possible to create a broadband data transmission link between a motor and an inverter without a du/dt filter at the inverter output.