Pull-in criterion for reluctance motors

Abstract

Discussion P. L. Alger (Consulting Engineer, Schenectady, N. Y.): This paper marks a very important advance in the art and, in my opinion, paves the way for a much greater use of synchronous motors for industrial and other purposes.In the first place, this new brush less synchronous motor can be built in totally enclosed fan-cooled and explosion-proof designs, just as induction motors are. This was not feasible heretofore, because of the problems of exposed sliding contacts and brush wear.In the second place, the substitution of the standard and inexpensive full-voltage induction-motor starting panel, for the complex and expensive synchronous motor starting panel formerly required, should make the new machine much more attractive commercially than existing types of synchronous motor. The automatic transfer of the field circuit from d-c supply to short-circuit through a discharge resistor and the reverse, as may be required on starting and peak overload conditions, eliminate the T H I S S U B J E C T is timely because of the recent improvement of reluctance motors t o a point where they have conr siderable sales volume. T h e pull-in criterion is related t o t h e maximum inertia t h a t can be pulled into step for a given frame size in t h e rating set on t h a t frame, expressed as a graph or b y an equation. This paper derives this equation. A reluctance motor is a synchronous motor without rotor excitation. T h e pull-in criterion for synchronous motors with d-c excitation was studied b y Edgerton a n d Fourmarier, 1 a n d b y Shoults, Crary, a n d Lauder. 2 Although their results cannot be applied t o t h e reluctance motor directly, they were found useful in checking certain steps.When t h e pull-in criterion is shown graphically, each frame size will have curves as in Fig. 1. T h e abscissa denotes the rating, in horsepower (hp), of t h e frame for high moment of inertia, / . T h u s if a large inertia must be pulled into step, t h e rating m u s t be reduced. T h e troublesome field relays and contactors which were required with synchronous motors.In the third place, it should be feasible to design the new motors for lower starting currents than induction motors of comparable performance, since the synchronous machine amortisseur winding is not called upon to carry the running current. This should make the new machines attractive for air-conditioning applications, where many schemes, such as part-winding starting, have been employed to reduce the inrush current.Finally, because of the very small field excitation requirements, it should be feasible to apply automatic programming devices to this excitation supply. This should enable the motor to have high power factor for limited periods when charges due to a power factor clause make this desirable. It may also have high breakdown torque under short-time overload conditions. That is, the motor can be designed with a relatively small air gap and in an economical frame size, and yet have the output and high power factor of a considerably larger frame size for ...

Line-Start Synchronous Reluctance Motor With V-Shaped Rotor Laminations

“…Here, 𝑚 is the number of phases, 𝑝 is the number of poles, 𝑇 𝑟𝑒𝑙 is the average reluctance torque, 𝐿 𝑚𝑑𝑠 and 𝐿 𝑚𝑞𝑠 are d-and q-axis magnetizing inductances, 𝑖 𝑑 and 𝑖 𝑞 are dand q-axis currents. A detailed derivation of the asynchronous and reluctance torques is reported in [26], [31], [32]. Ignoring the friction coefficient, the dynamic equation of the SynRM with cage bars that governs the torque balance at the shaft is generally expressed by [26]:…”

FE-Aided Synchronization Analysis of Line-Start Synchronous Reluctance Motors

“…However, the algebraic formulations described in [14][15][16][17] are still useful to approximate the synchronization process because numerical analysis by the FEA is computationally expensive. A relatively simple criterion for determining the synchronizing ability of LS-SynRMs is reported in [18]. Effort has also been made in [8] using a lumped parameter model to approximate the transient state of a LS-SynRM; however, the model was not accurate when compared to the FEA results.…”

Fotovoltaik Panel ile Beslenebilen SynRM Tasarımı ve Kontrolü

“…Fakat alan yönlendirme kontrollerin (FOC, Field Oriented Control) bu çalışmaların yapıldığı zamanlarda henüz bilinmemesinden dolayı bu * Sorumlu yazar: gboztas@firat.edu.tr. Yazarların ORCID Numarası: 1 0002-1720-1285, 2 0001-8142-1146, 3 0003-0491-8348 araştırmacılar pratikte relüktans motoru elde edememişlerdir. IM'lere benzer stator yapısına sahip SynRM'ler üzerine ilgi 1960'lara dayanmaktadır.…”

“…Güç elektroniği teknolojisinin gelişmesiyle birlikte tüm bu problemler giderilmiştir. Elektrik enerjisinin tasarrufu için artan ihtiyaçlar ile birlikte endüstriyel üreticilerin SynRM'lere olan ilgisi artmıştır [2][3][4]. Daha sonraki yıllarda değişken frekanslı sürücülerin kullanılmasıyla birlikte SynRM'lerin daha doğru analiz edilmesi ve daha doğru motor tasarımı yapılması sağlanmıştır.…”