Diagnostics for the 24 Vdc and 3.3 Vdc Backplane Voltages

The BMXCPS4002S, BMXCPS4022S, and BMXCPS3522S safety power supplies automatically provide detection for an overvoltage, overload, or short-circuit condition that may occur with respect to both the 24 VDC and 3.3 VDC Backplane Voltages.

If the power supply detects one of these conditions on the 24 Vdc voltage, the following occurs:

  • The power conversion function is shut down for the entire backplane.

  • A RESET command is issued for all modules in the rack.

  • The power supply OK LED is turned OFF.

  • The entire PAC is powered down.

If the power supply detects one of these conditions on the 3.3 Vdc voltage, the following occurs:

  • The power conversion function is shut down for the 3.3 Vdc backplane voltage.

  • A RESET command is issued for all modules in the rack.

  • The power supply OK LED is turned OFF.

  • Operation of the entire PAC program is stopped, although some PAC circuits may continue to receive power.

In either case, to recover from these conditions, take the following steps:

  1. Power down the primary power line.

  2. Check the compatibility between the estimated power supply consumption of the PAC against the capacity of the M580 safety power supply module on the 24 Vdc and 3.3 Vdc backplane lines.

  3. Eliminate the cause of the underlying condition.

  4. Wait for 1 minute after power down.

  5. Apply power on the primary line to restart the M580 safety power supply module.

Alarm Relay Contact Diagnostics

The BMXCPS4002S, BMXCPS4022S, and BMXCPS3522S safety power supplies present a two-pin alarm relay contact that you can use to obtain the following information:

  • If the relay is activated (i.e. closed):

    • Both the 24 Vdc and 3.3 Vdc backplane voltages are OK; and

    • RESET is not active.; and

    • If the power supply is placed in the main local rack:

      - the CPU is operational, and

      - the CPU is in RUN mode.

  • If the relay is de-activated (i.e. open):

    • Either or both of the 24 Vdc and 3.3 Vdc backplane voltages are not OK; or

    • RESET is active; or

    • If the power supply is placed in the main local rack:

      - the CPU is not operational, or

      - the CPU is in STOP mode.