Abstract: Methods and apparatus for energizing a wound component are described. In one arrangement, a method of energizing a component with an alternating voltage is provided. The component comprises a coil wound on a magnetic core. 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 is subsequent to the first time period. The second waveform comprises an oscillating function comprising a sequence of identical waveforms. 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.

Abstract: Methods and apparatus are disclosed for measuring an electrical current, particularly an AC electrical current, for example to measure a frequency response of a transformer. In a disclosed arrangement, a connection is made of a current input terminal for receiving a current to be measured to an input terminal of a differential amplifier via a portion of a resistive network. The resistive network holds the current input terminal at a ground voltage and the two input terminals of the amplifier at a common finite voltage above the ground voltage. The amplifier provides as output a measure of the current to be measured.