Transformer Noise (46 dB) v.s Ambient Noise (52~55dB)


High Lights of Low Noise Transformer;

  • 1 Unit 448MVA, 345/11kV, 65 dB at 448 MVA, NEMA Std exported to Central Maine Power Co., USA and received repeat order
  • 1 Unit 20MVA, 34.4kV, exported to USA (55dBA) OLTC
  • (3-year contract) 25MVA, 33kV, Sound Pressure Level 46 dBA
  • 6 Unit 200MVA, 345/115kV, 65 dB at 200 MVA, NEMA Std exported to Eversource Energy, USA and received 3 Unit repeat order
  • 450MVA, 345/115kV, 70 dB at 450 MVA, NEMA Std exported to Northeast Utilities System, USA

2. Cooling equipment noise

Fan and pump noise is mostly broadband with insignificant low frequency tones.

3.Load Noise


Load noise is mainly generated by the electromagnetic forces that result from the interaction of the load current in the windings and the leakage flux produced by this current. Another source of load noise is tank vibrations caused by the leakage flux impinging on tank walls. The main frequency is twice the supply frequency, ie, 100 Hz for 50 Hz transformers and 120 Hz for 60 Hz transformers. Transformer load noise increases with the load. Also, at higher loads, fans ramp up and add further noise

There are three sources of sound/noise in power transformers:

1. Core Noise


Core noise is caused by the magnetostriction property of core steel. It has components at multiples of 100 or 120 Hz (for 50 Hz and 60 Hz transformers, respectively). The relative magnitudes of the noise at the various harmonics is dependent on core material, core geometry, operating flux density and how close the resonance frequencies of the core and tank are to the exciting frequencies

Typical frequency spectrum of noise produced by a 60 Hz power transformer (Lp = sound pressure level)

Noise components and total noise of a 250 MVA transformer

Completed in 2007Low Noise Testing Room

Low Noise Transformator