When two inverters are used to control a dual winding motor in a master-follower setup, the system's controller or PLC sends the run command and references to the master inverter, and the master inverter will relay the commands automatically to the follower inverters.
The master and follower inverters will communicate through a CAN bus connection, which can be the same CAN bus used for the PLC-to-master communication, or a separate CAN bus only between the master and followers. Note that the fault clear command is not relayed; in case the follower inverters trip, the system controller has to send the fault clear command directly to the slave inverters (or the slave inverters can be reset via PowerUSER, or a power cycle of the 24 V auxiliary power).
Note: the master-follower feature is only supported in firmware version 7. See the Multi-inverter drives article for more information about using several EC-C inverters in parallel.
Recommended procedure for setting up the configuration:
- You can choose which CAN bus connection of the inverter is used for the master-follower function from the parameter group master_follower (1300) with the parameter can_channel (1300.2).
- The master and follower unit ID’s must be configured so that the inverters can communicate with each other via the CAN bus and the master unit will control the follower units correctly. The parameter id (1300.3) should be set to 0 for the master unit, and 1, 2, 3,... for the slave units. If only one slave is used, set the id of the slave to 1.
- After the ID's are set, the master-follower function can be enabled for all inverters with the enable (1300.1) parameter. Reboot the inverters after enabling to allow the master-follower function to activate correctly. Other settings of the master-follower function should be left at the default values.
- The limit settings of the follower inverters should be always set to be less strict than the limits of the master inverter by approximately 2 to 5 percent. For example: if the overvoltage trip limit of the master inverter is 850 V, the overvoltage trip limit for the follower inverters should be set to about 870 V. If the minimum torque limit of the master is set to -1.2 pc, the minimum torque limit of the follower inverters should be set to -1.25 pc, and so on. Over- and undervoltage controllers can be disabled for the follower inverters, they are only needed for the master inverter.
Note: The master-follower function does not share the resolver signal to the followers automatically. If the master inverter is running in closed-loop control with a resolver, the slave inverters have to receive the resolver signal via the SYNC link connection, or they can be used in open-loop control without a resolver.