Energizing coil wound on magnetic core and oscillatory testing of transformer

A method of energizing a component with an alternating voltage, the component comprising a coil wound on a magnetic core, wherein the method comprises:

• applying a voltage across the coil that has a first waveform during a first time period and a second waveform during a second time period, the second time period being subsequent to the first time period, wherein
• the second waveform comprises an oscillating function comprising a sequence of identical waveforms;
• and
• the first waveform is such that if the coil had zero electrical resistance the variation of flux density in the magnetic core with time would change sign at least once during the first waveform, wherein a single period of the oscillating function consists of a first half-cycle lasting half the period and a second half-cycle lasting half the period, the second half-cycle being subsequent to the first half-cycle,
• the first waveform is made up of a modified portion and an unmodified portion, the unmodified portion being subsequent to the modified portion, wherein the modified portion is different from the first half-cycle of the single period and the unmodified portion is identical to the second half-cycle of the single period, and
• the modified portion is such that the maximum flux density reached at any time during a time period equal to half the period of the oscillating function, from the start of the first waveform, is reduced in comparison to what would be the case if the first waveform consisted of a single period of the oscillating function.