This was originally posted on APC forums on 1/24/2012
I have a SUA1000RM2U that has a loud buzzing and humming in the transformer. When the AC power is removed and it kicks over to the battery power the transformer buzzes loudly then quiets down some but still is a hum that abnormally loudl. The greater the power draw, the quieter it is. Is this normal? Is this a sign that it might be going bad? Otherwise, it seems to function normally. - Thanks!
This was originally posted on APC forums on 1/26/2012
thank you for your question.
I also think about that problem some days ago.
I will try to give some answers from my point of view.
- Yes, it is very loud noise, for example 50 to 55 dB (A)
- Yes, this kind of UPS for example Rack Mount UPS are for Server Rooms with Racks in it
But, what exactly is the source of that loudness?
- If you have an Online UPS the AC Voltage is "changed" into DC voltage.
- With this DC voltage the Battery is always loaded
- And further the voltage from the Battery is "changed" into AC voltage which is given to Server, Workstations and other equipment
A Try to answer the question
- Such UPS has some Switched-Mode Power Supply. They use NOT a frequency of lets say 50Hz but they use much higher frequency, for example 20 kHz.
- Also such UPS has an Inverter. You need this to chop the DC voltage from the Battery to "create" AC voltage.
- Also there are a lot of electronic devices.
- All this together but especially the inverter makes this noice.
Message was edited by: Magnussen
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