ABSTRACT
In high-performance drives and servos, permanent-magnet electric machines are used. For fractional-, medium-, and high-power (in some applications, 10,000 kW) drives, threephase induction machines are frequently utilized. Fractional horse-power industrial and consumer drives employ low-cost single-and three-phase induction machines [1-6]. Induction electric machines, compared with permanent-magnet motion devices, have much lower torque and power densities, may not be effectively used as generators, but require simple electronic and control solutions in the motor (drive) operation. Induction motors were invented and demonstrated by a generous scientist and engineer
Nicola Tesla in the 1880s. Nicola Tesla made indispensable contributions to science and engineering inventing many electric machines, electromagnetic devices, radars, etc. Nicola Tesla integrated his induction motors with the matching polyphase power electronics demonstrating the speed control capabilities in 1888. Having underlined extraordinary engineering and technological developments performed by Nicola Tesla, it must be emphasized that he made a significant contribution not only to device physics of electromechanical and electromagnetic motion devices, but also to theoretical electromagnetics. In particular, in 1882, Nicola Tesla pioneered and developed the theory of the rotating magnetic field which is a cornerstone principle of electromechanical motion devices. He designed and demonstrated a two-phase induction motor in 1883. The first three-phase squirrel-cage induction motor was invented and demonstrated by Michail Osipovish Dolivo-Dobrovolski in 1890. These induction motors have been used for almost 120 years. In squirrel-cage induction electric motors, the phase voltages in the short-circuited rotor
windings are induced due to time-varying stator magnetic field as well as motion of the rotor with respect to the stator. The phase voltages are supplied to the stator windings. The electromagnetic torque results due to the interaction of the time-varying electromagnetic fields. The images of 250 W induction motors (left and at the center machines) are illustrated in Figure 5.1. For the illustrative purposes, a 250 W permanent-magnet synchronous machine (which is much smaller as compared to induction machines of the same rated power, and allows much larger overloading capabilities) is provided as the third image. To design electric machines, analyze them and evaluate their performance, one may
perform sequential steps starting from machine synthesis and optimization to modeling, simulations, testing, characterization, etc. It is unlikely that one may significantly improve the technology-centered designs of electric machines which have been successfully performed by different manufacturers. Stand-alone books concentrate on induction machine
Analysis, and Design with
design, and various tasks involved (three-dimensional electromagnetic, mechanical, thermal, vibroacoustic, structural, and other designs) are supported by various electric machine design tools. In general, the machine design and optimization are of a great importance. The machine design tasks are beyond the scope of this book. For specific classes of electric machine, the designs are covered in highly specialized books. Though the need for a machine design is obvious, only a very small fraction of engineers are involved because an optimal machine design is a narrow highly specialized problem. Sound solutions are available and have been finalized within more than 100 years for existing broad lines and numerous series of DC, induction and synchronous machines. In contrast, the power electronics, microelectronics, and sensors have been rapidly developed providing tremendous opportunities to advance electromechanical systems. Furthermore, the application and market for electric drives and servos have being notably expanded (avionics, bioengineering, electronics, etc.) in addition to the conventional automotive, power, robotics, and transportation areas. Therefore, we focus on the electromechanical system design issues considering electric machines as a key ready-to-use component rightly assuming the existing optimal-performance design of stand-alone electric machines. We concentrate on the systems design in order to guarantee best performance and achievable capabilities. Other important point is that through optimization and synergetic control activities, one improves the machine performance and capabilities enabling better energy conversion, torque production, losses reduction, vibration, noise minimization, etc. That is, we enable and enhance machine capabilities refining stand-alone machine design deficiencies or imperfections. This chapter reports sound analysis (modeling, simulation, performance=capabilities
assessment, and other tasks) and control of induction motors in the machine (phase) variables. Though the quadrature and direct reference frame can be used [1-6], the related concept (such as vector control and other approaches) may not offer advantages and provide any benefits due to the need for the most advanced DSPs to perform the associated direct and inverse transformations in real time [5,6]. Furthermore, all electric machines are operated and controlled only by using machine variables. For example one varies the phase (machine) voltages uas, ubs, ucs and uar, ubr, ucr while the directly measured currents are the phase (machine) currents ias, ibs, ics and iar, ibr, icr. For the squirrel-cage induction motors, one uses uas, ubs, ucs and ias, ibs, ics because uar, ubr, ucr are not supplied and rotor windings are short-circuited. It will be documented that the highest acceleration capabilities and minimal settling time can be achieved utilizing the high torque pattern (the so-called
frequency control), though to reduce the losses one may use the voltage-frequency control. These control concepts in the machine variable comply with the power electronic and hardware solutions.
