Contactor control by Manager Controller

    This article explains the considerations that need to be taken into account when the main contactor is not controlled by the individual AC Motor Controller.  

    In vehicle that contain multiple motor controllers, it is common that a single contactor is shared across the various power devices. In those cases, often, the main contactor is controller by a 3rd party System Manager controller, a Curtis 1350 or 1351 System Manager controller, or one of the VCL-enabled Curtis AC Motor controllers that serves as a System Manager controller. 


    Required Periodic Messaging
    Manager to Ancillaries
    • Pre-charge Enable (bit in command-word)
    • Interlock Enable (bit in command-word)
    • Emergency Shutdown (bit in command-word)

    Ancillaries to Manager
    • Motor Control Active (bit in status-word)
    • Capacitor Voltage (16 bit OS variable, or reduced resolution 8-bit VCL variable)
    • System Action (32 bit OS variable, or simplified/modified 16-bit or 8-bit VCL variable)


    Startup Sequence without or with passive weld-check
    1. Manager compares ancillary capacitor voltage with keyswitch voltage, a voltage delta is expected in case the main contactor has not welded. Only move to the next step if the capacitor voltage is at least 3V lower than the keyswitch voltage. In case of a rapid re-enable, this step make take a long period of time, as it relies on a slow passive discharge.
    2. Manager sends pre-charge enable bit to ALL ancillaries
    3. Manager compares ancillary capacitor voltage with key-switch voltage, the delta shall be less than 3V.  Once the threshold has been met, move to the next step   
    4. Manager closes the main contactor
    5. Pre-charge bit to all ancillaries must be cleared
    6. Interlock may now be set and cleared for each individual Ancillary, depending on operator interlocking logic

    Startup Sequence with active weld-check
      1. Manager sends pre-charge enable bit to ALL ancillaries
      2. Manager compares ancillary capacitor voltage with key-switch voltage, the delta shall be less than 3V. Once the threshold is met, move to the next step
      3. Manager disables pre-charge to ALL ancillaries
      4. Manager briefly enables, then disables interlock to one or more ancillaries, minimum field current must be set to draw-down the capacitor bank
      5. Manager checks capacitor voltage, the capacitor voltage must have lowered by at least 1V from last measurement
      6. Re-enable pre-charge bit to ALL ancillaries
      7. Manager compares ancillary capacitor voltage with key-switch voltage, the delta shall be less than 3V.  Once the threshold has been met, move to the next step 
      8. Close the main contactor
      9. Pre-charge bit to all ancillaries must be cleared
      10. Interlock may now be set and cleared for each individual Ancillary, depending on operator interlocking logic

      Shutdown Sequence
      1. Interlock bit must be cleared to all ancillaries
      2. Manager controller must monitor the Motor Control Active bit for each ancillary, and wait for all ancillaries to get to a safe state (Stopped, EM Brake Set), and stop motor control
      3. Main contactor may be opened

      Emergency Shutdown Sequence
      Manager must monitor the "ShutdownMainContactor" (bit 0x02) in the System Action word from each Ancillary. In case any Ancillary request the main to be open, or another device reports a critical fault (such as BMS), manager must immediately: 
      • Open the main contactor
      • Send a Emergency Shutdown bit to each ancillary


      Other Considerations
      There must be timeout check on the periodic messages on both Manager and Ancillary. In case of timeout, the worst case should be assumed by both Master and Ancillary, initiating emergency shutdown.

      Never close the contactor while the capacitor voltage is low. Not only will this cause high-inrush current, but also, a low capacitor voltage could indicate a critical controller failure in which case B+ shall not be applied.


      TACT Template for sequence verification and debug
      [TBD]

      VCL sample code
      [To be posted on Bitbucket]
      Emergency shutdown but shall trigger VCL fault with FAULT_ACTION_ShutdownAll fault action (or at a minimum FAULT_ACTION_ShutdownMotor + FAULT_ACTION_ShutdownEMBrake)

      For more information, please see this Technical Application Note