350 Hertz tone after power surge or self-test (Smart-UPS SMC1500IC)

[Rivanni]

My Smart-UPS SMC1500IC produces a continuous tone of 350 Hertz after a power surge or the weekly self-test. After approximately an hour, I hear some click, and the sound stops.

It is very unpleasant. I can hear in the whole room, not just near the UPS.

What is causing this tone?

Is it indicating something malfunctioning?

I have an older SMC1500I, and it doesn't make this sound.

[Teken]

Provide all the logs from APC Power Chute software / NMC / LCD: Event, Data, UPS

[Rivanni]

I only have an Event and Data log. I don't know what you mean by the others. PowerChute Serial Shutdown doesn't offer more log options. The logs were empty, by the way.

I performed a Runtime Calibration Status and then a Self Test.

During the calibration, the sound was very loud. After the self-test, it seems a bit less loud than the previous self-tests or power surges.

[Teken]

The sound you hear is from the unit going into battery only mode. The noise is from the inverter circuitry such as the transformer.

Based on the limited information you have provided from the logs. The system is operating as designed and running in AVR / Battery only mode as the input power is considered dirty.

You may consider making changes to the Power Quality, Green Mode. I have appended the full user manual for your specific model UPS:

https://download.schneider-electric.com/files?p_enDocType=User+guide&p_File_Name=SU_UM_990-5444E_MN0...

To enter configuration mode is explained in page 11. Power Quality is on page 12, Green Mode page 13.

Changing the power quality will force the system to accept a wider input voltage. Disabling Green Mode will bypass some internal circuits and consume more power (energy).

NOTE: APC PCSS must be running continuously on the target computer system to capture and record the historical event, data, ups logs.

Questions Ask . . . 👍 

[Rivanni]

Thank you for answering.

According to the status page, the display, and the event log, the UPS is not running in battery mode.

When is the power considered dirty? It all seems pretty stable.

The Green mode was exited when the calibration started. I don't know why it did not re-enter it.

Why do I always hear this sound after a self-test? If power is dirty, it would be random throughout the day, which isn't the case. 

Normally, the sound would be gone about an hour after the self-test, but it's still happening.

I applied the two settings (lower quality and disable green mode), but there was no change.

[Rivanni]

Since the sound kept going and was causing a headache, I decided to re-enable the Green mode again because that was the step that did not occur after a self-test. And sure enough, the sound stopped.

I'll monitor this and check if switching to Green mode resolves the issue again, should it recur.

[Teken]

When the phrase (Dirty Power) is used it is a general catch all statement. Dirty power can be low / high voltage, frequency drift, fast voltage transients, excessive THD.

The limited amount of logs you provided indicated the voltage was low as such the system went into AVR Mode. Thus, boosting the low voltage to an acceptable output level.

Should the input voltage be too far out of the AVR circuit. The system will transfer to battery only mode (inverter DC -> AC).

The system will remain in this state whether (AVR / Battery Only) until specific input power quality has been restored for X period of time.

Green Mode: 

https://www.apc.com/us/en/faqs/FAQ000264322/