What causes a transformer to vibrate?
The main cause of a transformer vibration, hence noise, is the so called magnetostriction effect. In simple terms, upon the exposure to a magnetic field, a magnetic steel gets magnetized, thus, extends. When the magnetic field is turned off, the sheet shrinks back to its original form. This cycle of extension and contraction is usually small dimensionally and therefore cannot be seen be the naked eye. Nevertheless, it is sufficient to cause vibration and, hence, noise. In transformers, the alternating voltage and current in the windings produce magnetic field in the transformer and its surroundings. However, the magnetostriction effect is manifested primarily in the core and tank because they are made of ferromagnetic steel. Unfortunately, transformers are commonly installed in residential areas. As a result, there are strict regulations on transformer’s vibration and noise. Consequently, transformers must be carefully designed and tested to satisfy such regulations.
3 phases power transformer, with magnetic shunts, surrounded by a tank
Simulate it before you build it
A transformer can cost millions of dollars. That’s why the simulation and validation of all performance aspects of a transformer can save you money and time. The popular EMWorks’s low frequency software package, EMS, is the preferred simulations platform for many transformer’s designers and manufacturers because it addresses all aspects of a transformer’s design. Since magnetostriction effect is directly related to the magnetic force density and the displacement, i.e., related to stress, in the core and tank, in the following paragraphs will present such results using EMS and SolidWorks. The total rigid body force acting on the windings is equally important because it can cause the windings to vibrate or even break altogether.
Rigid body force in the coils, tank, core, and magnetic shunts
Magnetic force density in the core
Magnetic force density in the shunts
Displacement in the shunts –not true scale
Mechanical stress in the core –not true scale
Reaction force in the tank –not true scale
Strain in the windings –true scale