Switched Reluctance Motor, Construction, Performance

 

Switched Reluctance Motor, Construction, Performance, and Drive
Systems

Introduction and Research Objectives

             Work has been guided towards reluctance motors particularly switched reluctance motors (SRM) according to the creation of power electronics and computer science. For industrial applications the switched reluctance motor (SRM) drives are of recent origin. For variable speed applications a variable reluctance motor has been suggested since 1969. The roots of this motor can traced back to 1842, but thanks to the introduction of inexpensive, high-power switching tools the "reinvention" became feasible. The switched reluctance motors are identical to the stepper motor which assumes that it normally has less poles with a greater stepping angle of one tooth per pole, Better power output potential and the shifted reluctance motor is usually controlled with shaft feedback to synchronize the phase currents with specific rotor locations while the stepper motor is usually worked in the open circle, i.e. without shaft location feedback. Switched reluctance motor is usually designed to transform large volumes of power efficiently; Stepper motors are most generally equipped to retain integrity controls in the phase role [1] [2].

Content

           Switched Reluctance Motor [SRM] is also known as Variable Reluctance Motor. This motor works on the principle of variable reluctance. This means, the rotor continuously attempts to adjust along the most minimal reluctance way. A switching power semiconductor circuitry (inverter) is necessary for the Switched Reluctance Motor operation, as the name implies.

      We will talk about these topics in this subject:

Construction.      

Performance.                                                              

Drive Systems.                               

                                                                                        Switched Reluctance Moto              

      First: Construction of Switched Reluctance Motor:-

Switched Reluctance Machine or variable Reluctance Machine has two designs:

Single Salient Construction and Doubly Salient Construction,

Stator and magnetic rotor circuits are laminated to minimize core losses in all types of Switched Reluctance Machine.

    Singly Salient Construction:

         A singly salient SRM construction comprises of a non-salient stator and a salient two poles rotor. The rotor does not have any winding wound over it but the stator have two phases winding as shown in figure (a).

                                                      It should be remembered that, in actual SRM the number of phases winding on stator might be larger than two, but The rotor is of salient design and the inductance of the stator winding process differs with the location of the rotor. The inductance becomes minimal where the rotor axis and the stator process winding axis overlap while average when all axes are squared.

  

  Doubly Salient Construction:

Unlike the single-significant form, the double-significant Switched Reluctance Motor stator is of outstanding construction and consists of four poles as seen in figure (b), the rotor does not have winding and is of outstanding construction but has two poles. So this type of SRM is a heteropolar motor where stator numbers and rotor poles are different.

          The windings of the stator process are condensed to wind. These concentrated windings on radially opposite poles are connected either in series or in parallel to result in two phase winding on the stator.

          For the same scale, a doubly salient form Switched Reluctance Motor or variable Reluctance Motor generates more torque relative to the singularly salient kind. A doubly SRM is also more growing and commonly used.                                                                     Another fig for doubly construction

The stator is composed of stampings composed of silicon steel with planned within poles. The stator's number of poles will either be an even number, or an odd amount. Most accessible motors also have a range of stator poles (6 or 8). Both these poles hold spindles on the ground. The fields coils of opposite poles are bound in series such that their mmf are additive and phase windings are named. Individual coil or a group of coils constitute phase windings. Each of the windings in process is connected to the motor terminal. Such terminals are suitably attached to a control semiconductor switching circuitry's output terminals, whose input is a dc surge.

The rotor also consists of silicon steel stampings with planned poles to the outside. The number of rotor poles is distinct from that of stator poles. The number of rotor poles in most of the available motors is 4 or 6 depending on the number of 6 or 8 stator poles.

             The shaft of the rotor carries a sensor of location. Signals obtained from the rotor location sensor affect the turning ON and turning OFF function of the different control semiconductor circuit devices.

          Second: Switched Reluctance Motor Performance:-

      In realtime systems there are essentially three variables available for power. During low-speed operation, torque or speed regulation can be accomplished simply by changing the current relation while retaining the regulation angles set. However, this will not effectively drive the drive since the machine generates some degree of negative torque during the free wheel portion of the phase current after turning it off in the aligned position [3]-[4]-[5]. In certain high-technology systems, such as electric and hybrid vehicles, optimizing output in terms of increasing capacity is a beneficial function. With optimization strategies, drive efficiency can be enhanced under which all variables are used for real-time power. Any concrete roles may be chosen and used for optimisation purposes, depending on the requirement. For eg, torque can be maximized per ampere or output, or torque ripple can be reduced with correct power. The basic theory of such objective functions is mentioned below:-

    1. Maximizing Torque per Ampere

Torque per ampere shows the torque output capacity for a given ohmic failure. Optimizing this ratio is similar to finding a true minimum of total motor losses for a given processing capacity, and thereby immediately optimizing the performance. During low speed service, a collection of control variables can be chosen for. operating stage, either by real-time search [4], [6] Or using neural networks[7],[8] or lookup tables to optimize the torque per ampere. However, only the control angles are accessible for optimisation purposes during high-speed operation[7],[8].

   2. Torque Ripple Minimization

               For certain systems, such as electric power steering, it is preferred not to have torque ripple induced by phase commutation. The torque ripple can be reduced by properly profiling the stator process currents which can be accomplished utilizing neural networks [9], [10], [11]. The amplitude of the current reference to be set for increasing rotor location is determined in real time, and is used in the control technique to reduce the torque ripple.

Both the performance enhancement strategies described above include knowledge about the continuous rotor position with sufficient precision and resolution. While the rotor location can be sensed with reasonable precision and resolution by means of mechanical location sensors, it is a real challenge to realize it with less power by the sensor. Much of the fewer techniques of the sensor provide details about the rotor 's location on the inductance profiles at distinct stages, which is only enough to conduct phase commutation and operate the motor. The goal of this research is to obtain less sensor control that would provide continuous location information with good precision, resolution and bandwidth in order to incorporate any required performance optimization technique.

                                                              References

[1].                   R. Krishnan: “Switched Reluctance Motor Drives Modeling, Simulation, Analysis, Design and Applications,” London, CRC press, 2001.

[2].                   L. Xu and E. Ruckstadter, “Direct modeling of switched reluctance machine by coupled field-circuit method,” IEEE Trans. Energy Conv., vol. 10, pp. 446–454, Sept. 1995.

[3].                   Gopalakrishnan, S. (2000). Inductance model based sensorless switched reluctance motor drives for high performance applications (Order No. 9968919). Available from ProQuest Dissertations & Theses Global. (304665692). Retrieved from https://search.proquest.com/docview/304665692?accountid=178282

[4].                   P. Tandon, A.V. Rajarathnam, M. Ehsani, “Self-Tuning Control o f a Switched Reluctance Motor Drive With Shaft Position Sensor,” IEEE Transactions on Industry Applications, Vol.33, No.4, July/August, 1997, pp. 1002-1010.

[5].                    P.C. Kjaer, P. Nielsen, L. Andersen, and F. Blaabjerg, “A New Energy Optimizing Control Strategy for Switched Reluctance Motors,” IEEE Applied Power Electronics Conference, 1994, pp. 48-55. (http://iel.ihs.com)

[6].                    G. Suresh, K.M. Rahman, B. Fahimi, M. Ehsani, “Self-Tuning Sensorless SRM Drives for Low-cost Mass Production,” IEEE Industry Application Society Annual Meeting, St. Louis, October, 1998, pp.593-600. (http://iel.ihs.com)

[7].                    K.M. Rahman, G. Suresh, B. Fahimi, A.V. Rajarathnam, M. Ehsani, “Optimized Torque Control o f Switched Reluctance Motor at All Operational Regimes Using Neural Network,” IEEE Industry Application Society Annual Meeting, St.Louis, October, 1998, pp.701-708.

[8].                    K.M. Rahman, G. Suresh, B. Fahimi, A.V. Rajarathnam, M. Ehsani, “Optimized Torque Control o f Switched Reluctance Motor at All Operational Regimes Using Neural Network,” IEEE Industry Application Society Annual Meeting, St.Louis, October, 1998, pp.701-708.

[9].                   J. Moreira, “Torque Ripple Minimization in Switched Reluctance Motors via Bicubic Spline Interpolation,” IEEE PESC Conference Records, 1992, pp. 851-856. (http://iel.ihs.com)

[10].               K.M. Rahman, A.V. Rajarathnam, M. Ehsani, Optimized instantaneous torque control of switched reluctance motor by neural network,” IEEE Industry Application Society Annual Meeting, St.Louis, October, 1998, pp.556-563.

[11].               I. Husain, K. R. Ramani, and M. Ehsani, “Torque Ripple Minimization in Switched Reluctance Motor Drives by PWM Current Control,” IEEE Transactions on Power Electronics, Vol. 11, No. 1, pp. 83-88, 1996.

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