This article explains more about the PSM INP1 Failure Alarms being set and clear shortly without any activity on the customer side.

Check if we are seeing the below log messages:

2025-01-21 03:05:50 mcyat-hl3-1b mcyat-hl3-1b: craftd[11496]: %DAEMON-4: Major alarm set, PSM 1 INP1 Failure

2025-01-21 03:05:50 mcyat-hl3-1b mcyat-hl3-1b: craftd[11496]: %DAEMON-4: Major alarm set, PSM 4 INP1 Failure

2025-01-21 03:05:50 mcyat-hl3-1b mcyat-hl3-1b: craftd[11496]: %DAEMON-4: Major alarm set, PSM 7 INP1 Failure

2025-01-21 03:05:50 mcyat-hl3-1b mcyat-hl3-1b: craftd[11496]: %DAEMON-4: Major alarm set, PSM 10 INP1 Failure

2025-01-21 03:05:51 mcyat-hl3-1b mcyat-hl3-1b: craftd[11496]: %DAEMON-4: Major alarm set, PSM 13 INP1 Failure

2025-01-21 03:05:51 mcyat-hl3-1b mcyat-hl3-1b: craftd[11496]: %DAEMON-4: Major alarm set, PSM 16 INP1 Failure

Please check on the below lines:

- Do not mix AC and DC PSMs or different PDM types within a single system. << Not mixed in our router.

- The MX2000 line of routers configured for three-phase wye AC input power must use only three-phase wye AC PDMs and three-phase wye AC PSMs. 

- The systems configured for three-phase delta AC input power must use only three-phase delta AC PDMs and three-phase delta AC PSMs. The systems configured for single-phase AC input power must use only single-phase AC PDMs and single-phase AC PSMs.

In a three-phase AC power system, the AC power going to the PSMs is split into a pair of phases. Each PSM works on a single phase. This means the power system works independent of the kind of AC feed connected. You can connect one or two feeds, depending on the power system configuration, number of PSMs, redundancy, and so on. Each phase from each of the two feeds is distributed among one or two PSMs. One feed has each phase going to two PSMs and the other feed has each phase going to a single PSM. The PDM can receive up to six different phases for distribution among nine AC PSMs.

Now based on the above information the root cause can be as below:

• The input power fluctuation is seen on PSMs 1, 4, 7, 10, 13, and 16. These PSMs appear to be linked to one specific phase (e.g., Phase A) of the three-phase AC power system. A fluctuation in this phase can affect all PSMs connected to it. This issue can arise from:

Phase Imbalance- The power supplied to one phase might have slightly fluctuated, causing instability for all PSMs using that phase.

• If dual power feeds are used, one of the feeds might have inconsistent power delivery to the affected phase.

Reference Documents:

https://www.juniper.net/documentation/us/en/hardware/mx2020/topics/concept/mx2020-power-subsystem-overview.html

https://www.juniper.net/documentation/en_US/release-independent/junos/topics/concept/mx2020-ac-power-supply-module.html