Rotating field electrical motor driven systems are one of the key assets in reducing carbon emissions, since they are widely used in electrical energy production and end-use. This research project advances fundamental science in the field and develops new smart modulation methods for power converters. The power converters are used in diverse sectors, ranging from industrial to residential applications. In the industrial sectors the converters are used to rotate pumps, fans, conveyors, compressors as well as in heavy working machines and machinery. In transportation they are used in EVs, hybrid vehicles, trains, and ships and also aircrafts are becoming more and more electric. The voltage source converter is the most used power electronics configuration to enable accurate speed and torque control for rotating field machines. A DC voltage is modulated to AC voltage waveform using a pulse-width-modulation (PWM) technique. The PWM creates high frequency harmonic content to the voltage that causes an additional loss component to electrical machine. Generally, the amount of the harmonic losses is significant ranging from 5% to 50% of the electrical machines losses depending on the operation point. The additional harmonic loss component is not yet fully understood and it has been a controversial topic. To model the losses of the electrical machines with PWM-supply is still too complicated to be treated on a microscopic level. In the future, the FEM software employing advanced models can predict the electrical machine losses more accurately, but these kinds of models are far away from practical implementations. In here, a new research method to study harmonic losses were developed. The proposed electrical harmonic power approach is a simple and effective way to study the energy-efficiency of all electric apparatuses that utilize PWM. The approach will provide us the accurate data base to achieve precise results which the research will use for the development of a novel and efficient modulation method.