The core should be flat with intact insulation varnish film and tightly stacked laminations. The silicon steel sheets on the edges should not be curled up or wavy. The surface of all core parts should be free of oil sludge and impurities. There should be no short circuits or (lapping) between laminations, and the joint gaps must meet the required specifications. Read More

The magnitude of the main magnetic flux in a transformer core is determined by the excitation current. Since the no-load current of a transformer actually varies with its operating voltage, a higher voltage results in a larger no-load current, which in turn increases the excitation current. Conversely, a lower voltage leads to a smaller no-load current. Read More

The primary source of transformer noise is the core. Core noise is caused by core vibration resulting from the magnetostriction of silicon steel sheets and magnetic attractive forces. The magnitude of magnetostriction is related to the material of the silicon steel sheets and the tightness of the core; the higher the magnetic flux density of the core, the greater the magnetostriction of the silicon steel sheets. The condition of the stacking joints in the transformer core affects the flow of magnetic flux, causing the core to generate noise of varying degrees and magnitudes. If the AC power supply contains harmonic components, it will lead to increased noise. The fundamental frequency of core noise is twice the power supply frequency, along with noise at various integer multiples of that frequency. Additionally, electromagnetic forces between winding conductors or between coils can also cause vibration and lead to noise. The following are several countermeasures for suppressing noise: Read More