A Research in the Iron Loss and Harmonic Characteristics of Silicon Steel Sheets Operated Under Non-Sinusoidal Waveforms

Electronic machinery such as motors, transformers, and power generators is essential and common in daily life. Such equipment generally employs silicon-steel sheets as the material for the iron core. The different thicknesses and types of silicon-steel sheets used in the manufacture of various types of electronic machinery results in significant differences in efficiencies, characteristics, and energy losses.
Motors are now often supplied with a sinusoidal pulse-width-modulation (SPWM) input from electronic controllers rather than with a traditional sinusoidal waveform input, which makes it necessary to characterize the electromagnetic properties of silicon-steel sheets under nonsinusoidal waveforms such as SPWM.
In order to experimentally determine the iron losses and harmonic characteristics of silicon-steel sheets operating under nonsinusoidal waveforms, including in the research and development of a silicon-steel-sheet measurement system, a reusable and standardized toroidal test frame for testing toroidal laminated silicon-steel sheets was designed, and the electromagnetic properties of silicon-steel sheets operating under nonsinusoidal waveforms were analyzed.
This study referred to IEEE and ASTM standards when self-designing a detachable standardized toroidal test frame for measuring the iron losses of toroidal laminated silicon-steel sheets and for determine the effects of winding tolerances to allow precise comparisons of the characteristics of similar devices. The test frame can be used to measure the electromagnetic characteristics of various thicknesses of laminated silicon-steel sheet at high frequencies (50–5,000 Hz) and high magnetic flux densities (0.2–1.9 T). Moreover, it can withstand high temperatures (25–300OC) for a short period and can be operated under both sinusoidal and nonsinusoidal voltage waveforms.
The experimental content of this dissertation is divided into three parts: (1) research and development of a silicon-steel-sheet measurement system and the development and design of a reusable and standardized toroidal test frame; (2) analysis and discussion of the effects of the operating voltage waveform, modulation index, total harmonic distortion, and form-factor coefficient on the iron loss of silicon-steel sheets; and (3) analysis of the major and minor hysteresis loops when silicon-steel sheets are operating under nonsinusoidal waveforms. Moreover, the operation of laminated silicon-steel sheets under different modulation indexes and the excitation of secondary hysteresis curves relative to the total iron loss are discussed.
The results obtained for the relationship between the iron loss and modulation index in current electrical-motor designs incorporating silicon-steel sheets and operating under nonsinusoidal voltage waveforms such as SPWM, pulse could help to identify motor designs and voltage waveforms that produce smaller iron losses and higher working efficiencies.