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FIGURE 1. Photo of transformer equipment    through the windings of one coil creates   CRC) in Västerås, Sweden needed to
for high-voltage power lines.               a magnetic ux that induces current in      understand the inner workings of their
                                            an adjacent coil. The voltage adjustment   transformers in order to optimize their
in order to predict and minimize the        is achieved through different numbers      designs for minimal transformer hum.
noise levels in their transformers.         of coil turns.
Through the COMSOL Multiphysics®                                                       ð COUPLING ACOUSTIC,
simulation software and its Application        Because the core is made of steel,      MECHANICAL, AND
Builder, they have run virtual design       a magnetostrictive material, these         ELECTROMAGNETIC
checks, tested different con gurations,     magnetic uxes — which alternate            EFFECTS ALL IN ONE
and deployed their simulation results       direction — cause mechanical strains.
through customized user interfaces built    This generates vibrations from the quick   “We chose to work with
around their models.                        growing and shrinking of the metal.        COMSOL Multiphysics because it
                                            These vibrations travel to the tank        allows us to easily couple a number
ð SILENCING SOUND FROM                      walls through the oil and the clamping     of different physics,” said Mustafa
SEVERAL SOURCES                             points that hold the inner core in place,  Kavasoglu, scientist at ABB CRC. “Since
                                            creating an audible hum known as core      this project required us to model
Transformer noise often comes from          noise (see Figure 2, bottom).              electromagnetics, acoustics, and
several sources, such as vibrations in the                                             mechanics, COMSOL® software was
transformer core or auxiliary fans and         In addition to the core noise, the      the best option out there to solve
pumps used in the cooling system. Each      alternating current in the coil produces   for these three physics in one
of these sources needs to be addressed      Lorentz forces in the individual           single environment.”
differently to reduce noise.                windings, causing vibrations known as
                                            load noise that add to the mechanical         Kavasoglu; Dr. Anders Daneryd,
   ABB’s transformers comprise a metal      energy transferred to the tank.            principal scientist; and Dr. Romain
core with coils of wire wound around                                                   Haettel, principal engineer, form
different sections, an enclosure or tank       With these multiple sources             the ABB CRC team working with
to protect these components, and an         of noise and the interconnected            transformer acoustics. Their objective
insulating oil inside the tank (see Figure  electromagnetic, acoustic, and             was to create a series of simulations
2, top). Passing alternating current        mechanical factors at play, engineers at   and computational apps to calculate
                                            the ABB Corporate Research Center (ABB

FIGURE 2. Top left: CAD model of the active part of a three-phase transformer with windings mounted around the core. Top right: The active part of a
power transformer that is placed in a tank lled with oil. Bottom: The energy conversion chain for core noise and load noise generation (magnetostriction
in the core and Lorentz forces in windings).

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