Line starting capability of Synchronous Reluctance Motors (SynRM) is a crucial challenge in their design that if solved, could lead to a valuable category of motors. In this paper, the so-called crawling effect as a potential problem in Line-Start Synchronous Reluctance Motors (LS-SynRM) is analyzed. Two interfering scenarios on LS-SynRM start-up are introduced and one of them is treated in detail by constructing the asynchronous model of the motor. In the third section, a definition of this phenomenon is given utilizing a sample cage configuration. The LS-SynRM model and characteristics are compared with that of a reference induction motor (IM) in all sections of this work to convey a better perception of successful and unsuccessful synchronization consequences to the reader. Several important post effects of crawling on motor performance are discussed in the rest of the paper to evaluate how it would influence the motor operation. All simulations have been performed using Finite Element Analysis (FEA).

Studying crawling effect in Line-Start Synchronous Reluctance Motors (LS-SynRM)

One of the essential parts of a Synchronous Reluctance Motor (SynRM) for direct-on-line (DOL) applications is a damper winding (DW) which makes the start of the motor possible. However, the DW can also be a considerable source of Joule losses caused by DW currents reacting on the stator current linkage and permeance harmonics. In order to get a comprehension of how DW bars' distribution influences the amount of induced rotor Joule losses at steady state different designs of DW of a SynRM are considered in the paper. Also the authors consider different methods of minimising stator current linkage distortion and permeance harmonics by stator part modification: magnetic wedges, reduction of slot opening and short pitching. A comparison with an induction motor with the same stator was done as well.

Analysis of damper winding designs for direct-on-line synchronous reluctance motor

Single‐phase direct‐on‐line synchronous motor for a specific application in comparison with an induction motor

Direct-on-line synchronous reluctance motors (DOLSynRM) combine the characteristics of the induction motor (IM) and the synchronous reluctance motor (SynRM). Saturation of core materials, the eddy currents, and the asymmetry of the rotor core and cage make it difficult to predict to which kind of loads the motor can synchronize. In this paper, the DOLSynRM start-up is analyzed with a magnetic field decomposition that makes it possible to quantify and isolate forces between any two distinct parts of an electric machine using a time-stepping finite element (FE) field solution. The results show explicitly, which portion of the motor torque is produced by the rotor core and which by the rotor cage. Compared to conventional static and quasi-stationary analyses used to distinguish between the torque on rotor core and cage, the presented method gives a more detailed view.

Analysis of direct-on-line synchronous reluctance machine (DOLSynRM) start-up using a magnetic field decomposition

Self‐start synchronous reluctance motor new rotor designs and its performance characteristics

Line Start Synchronous Reluctance Motors (LSSRELMs) is one of the suitable solutions for energy efficient electric motors [1]. Because of reduced rotor mass, less cost, absence of permanent magnets and better efficiency these motors are becoming strong contenders for both induction motors and as well as line start permanent magnet motors [2]. This paper investigates four different rotor structures of 3 phase, 2.2 KW LSSRELM. Initially we designed an induction motor of 2.2 KW used in hermetic compressor. Soon after, using a common stator, LSSRELM has been designed. Even though LSSRELMs provide better efficiency (compare to induction motors), it suffers from poor power factor. Maximizing the saliency ratio leads to better power factor [3]. The saliency ratio depends on direct (d) and quadrature (q) axes inductances. Analytical approach to determine these inductances are found in [4]. In the chosen application two task are considered to develop a novel LSSRELM: (i) power factor and (ii) improvement in startup behavior under different loading conditions. The later criterion is much important in the design stage of LSSRELM because the starting and synchronization of the motor strongly depends on rotor parameters [5]. In this research, four cylindrical pole rotor structures with Aluminium and Copper combinations are investigated. At first, we study the synchronization capability for given load and inertia. Later, dynamic conditions and optimization process are carried out for the power factor improvement through FEA. To validate the designed model, prototype of all the models has been manufactured and tested. Different test results are finally compared with the FEA results. Experimental results show that the new structure provides better power factor, efficiency and pull in capability.

G. A. Uvaraj

Papers

A novel line start synchronous reluctance motor