This article proposes a four-coil unified model of electrical machinery (FUMEM) to uniformly describe the electromechanical energy transformation process of electrical machinery, which is an extended research work based on the concept of “entrainment electromotive force” previously proposed by authors.

Figure 1. The FUMEM proposed in this article

From the perspective of the physical model, the stator and rotor of the FUMEM are represented by their respective fixed spatial orthogonal two-phase excitation coils. There is no need to introduce the physical concept of the “pseudo-stationary coil” proposed by Kron and others. The FUMEM has an intuitive and concise electromagnetic structure. From the perspective of the mathematical model, with the introduction of the “entrainment electromotive force”, the spatial vector mathematical equations of the FUMEM can be established in any rotational reference frame without relying on additional coordinate transformation processes. This FUMEM is easy for understanding and memorization.

The main content of this article includes three parts. Firstly, it briefly reviews the development of the unified theory of electric machinery. Secondly, it provides a detailed introduction to the physical model of the FUMEM, establishes its magnetic flux, torque, and voltage spatial vector equations, and discusses its operation and control characteristics based on the established voltage and torque equations. Lastly, this article explores the application of the FUMEM to analyze and explain the operation processes of typical synchronous, asynchronous, and direct current motors.

The work presented in this article originates from teaching and research practice and provides a beneficial extension and complement to the unified theory of electrical machinery. With its double-sided excitation by two-phase alternating current, the FUMEM not only provides a comprehensive understanding for the electromechanical energy transformation process of electrical machinery, but also offers a conceptually clear and straightforward approach that can be easily comprehended and applied in various practical scenarios.

The work presented in this article also holds great reference value for practical applications. With the fundamental vector control architecture provided in the article, it is expected to achieve a unified vector control framework for different types of motors.

Figure 2. The fundamental vector control architecture based on the FUMEM