Noisy UPS Transformer

[Emad Shaaban]

Hello experts
DC UPS system supplied with 50KVA transformer , Recently Transformer humming (noise ) became up-normal . this start happened in different UPS system in our site.
humming Transformer was replace with new Transformer but the sound still high.
-Transformer output AC waveform was :
voltage wave is sinusoidal
current wave was distorted
TWD was 260
-UPS output DC was Pure
Please see attachments
Voltage

http://files.engineering.com/getfil...4b33-4c14-a32a-6edc9a13b105&file=IMG_2785.JPG

Current

http://files.engineering.com/getfil...4b33-4c14-a32a-6edc9a13b105&file=IMG_2785.JPG

 

[HamburgerHelper]

Does the sound increase or decrease with DC load? I think if it is with the capacitor or not having a large enough inrush reactor the noise should increase with load.

 

[Emad Shaaban]

Even if the load disconnected the sound still high