Design of low-torque-ripple synchronous reluctance motors

A design approach oriented to the minimization of torque ripple is presented for synchronous reluctance motors of the transverse-laminated type. First, the possible types of rotors are classified and the more suited rotor structure is evidenced, to be matched to a given stator. Then, the inner rotor design is described, pointing out the low-ripple measures. Lastly, experimental results are given from three different rotors; they confirm the validity of the proposed approach     

High-performance control of synchronous reluctance motors

Based on a (d,q) synchronous frame, the control problems of synchronous reluctance motors are outlined. In particular, the effect of magnetic saturation, core loss, and angular measurement errors of various types are evidenced. A flux-observer-based control scheme, capable of overcoming most of the above problems, is proposed. The proposed control has been implemented on a prototype drive, adopting a 17-N·m 8000-r/min motor. The experimental results show quite a good performance, with particular emphasis on those applications which require a large constant-power speed range     

Thermal analysis of induction and synchronous reluctance motors

In this paper, the thermal behavior of two induction motors (2.2 and 4 kW, four poles) and two synchronous reluctance motors [(SynRMs) transverse-laminated] are investigated and compared. Both motor types use the same stator but have different rotors. Using a lumped-parameter simulation program, a thermal analysis has been also carried out, and the obtained results have been compared with the experimental ones. A direct comparison of the thermal behavior of the two motor types has thus been made for constant load and constant average copper temperature conditions. Inasmuch as the SynRM has negligible rotor losses compared with the induction motor, it is capable of a larger rated torque, from 10% to more than 20%, depending on the relative size of end connections and motor length.     

Design refinement of synchronous reluctance motors throughfinite-element analysis

In this paper, the key points in the design of synchronous reluctance motors are first evidenced and discussed, that is, the choice of rotor type, the stator-rotor joint design, and the optimization of the rotor structure. A purposely designed finite-element code is then introduced and validated, on the basis of properly obtained experimental data. Measured and computed torques are compared, with emphasis on the evaluation of the torque ripple. Last, the finite-element method code is used to illustrate some aspects of the stator-rotor design and to show the torque-ripple performance of different types of machine structure     

Permanent magnet synchronous motors using primarily reluctance torque

Permanent magnet synchronous motors (PMSMs) are widely used in many applications as high‐performance variable‐speed drives. In traction drives, such as those used for electric vehicles or for the compressor drives of air conditioners, a wide constant‐power speed range and high‐efficiency operation are desired. The aim of this paper is to develop a high‐performance PMSM that offers high‐efficiency performance in the high‐speed region, including light‐load conditions, as well as a wide constant‐power speed range. Simulations show that the proposed interior PMSM, which produces chiefly reluctance torque and in which the permanent magnet flux assists torque production, is capable of meeting the above performance requirements. A prototype PMSM is designed in accordance with this new design concept and several drive tests are carried out. The saliency ratio of the prototype IPMSM is about 5, and, as a result, reluctance torque is the principal torque component, representing more than 70% of total torque. The prototype IPMSM can attain a constant‐power speed range of up to 5:1 with high‐efficiency drive in the high‐speed, constant‐power region. The proposed IPMSM is suitable for variable‐speed drives requiring high‐speed, constant‐power operation. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 60–68, 2001     

Impact of cross saturation in synchronous reluctance motors of thetransverse-laminated type

The cross-saturation phenomenon in synchronous reluctance motors is extensively analyzed, with a main reference to motors of the transverse-laminated type. A mixed theoretical and experimental approach is adopted, aiming at definition of the motor's behavior when large overload currents are driven up to ten times the rated current. As a consequence, a special test and measuring procedure has been adopted. The obtained results are used to check the validity of the adopted model and to prove the unexpected overload performance of this motor     

Determination of direct and quadrature axis inductances of synchronous reluctance motors with allowance for cross saturation

The d‐axis inductance of reluctance motor is affected by not only the d‐axis current but also the q‐axis current, because of cross magnetic saturation between the direct and quadrature axes. This situation is similar for the q‐axis inductance. The authors propose a method to determine the d‐axis inductance related to the d‐ and q‐axis currents and the q‐axis inductance related to the d‐ and q‐axis currents from a standstill test. This method involves the following four steps. First a rectangular‐wave voltage, alternated between plus and minus, is applied to the two armature winding terminals after breaking the rotor in the d‐axis position. Secondly, the voltage and current between the terminals are measured. Thirdly, the d‐axis inductance related with d‐axis current is calculated from the voltage and current. Finally, the process above is repeated when a DC current flows from the remaining armature terminal to neutral point terminal and the d‐inductance related to the d‐ and q‐axis currents is derived. A similar treatment applies when determining the q‐axis inductance related to the d‐ and q‐axis currents in the q‐axis rotor position. The method is implemented on a 1.1 kW–178 V–6.3 A‐4P–2200 min^?1 flux barrier type reluctance motor. Results of load performance on a vector controlled reluctance motor measured by on‐load tests and calculated from the d‐ and q‐axis inductances obtained by the proposed method clearly demonstrate the validity of the proposed method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 52–59, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10377     

Sensorless control of synchronous reluctance motors based on extended electromotive force model and inductance measurement

In this paper, sensorless control for synchronous reluctance motors (SynRMs) without signal injection and an inductance measurement for position estimation are proposed. In the case of SynRMs, accuracy of inductances is the most important factor in realizing precise position estimation because inductances are largely varied by a magnetic saturation phenomenon. Therefore, the inductance measurement method, which can measure appropriate inductances for position estimation, is important as well as a sensorless control method. The inductance measurement based on the observer is discussed, and the measurement method and the parameter adjustment method for improved stability of the closed loop are proposed. The proposed method can measure inductances easily and be applied for permanent magnet synchronous motors, too. Finally, the proposed sensorless control method is verified experimentally. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 70– 80, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ eej.20274     

Structures theory of reluctance step motors

Reluctance step motors are obviously adapted to such functions, but the number of steps depends on the product of the numbers of phases and of rotor teeth. In usual structures (those with regularly displayed stator salient poles, slotted or not) these numbers must obey certain relations, so that many numbers of steps are impossible to obtain, including, obviously, all the odd numbers. This article generalizes the structures of step motors and presents the methods of designing motors with a “dissymmetrical” stator. The theory also includes the usual “symmetrical” structures as well. The authors intend to show the possibility of obtaining almost any number of steps by changing the regular, symmetrical disposition of the poles into an irregular, dissymmetrical one, which allows odd numbers of rotor teeth, in particular. They also build a simple theory of the generalized structures of salient pole step motors. Various examples of dissymmetrical motors are given, which provide peculiar numbers of steps that can be useful in specific applications (robotics, angular and linear measurements, etc.)     

High-precision torque control of reluctance motors

The high-precision torque control of a reluctance motor for servo applications is described. The prototype is a three-phase, eight-pole reluctance motor driven by a MOSFET inverter. The current control and the speed control are performed by software of the digital signal processor TMS 32010. The motor is supplied by sinusoidal current, and two current control methods are proposed. One is based on a vector control principle to achieve the linearity between current and torque, and another is developed to obtain the maximum torque/current ratio. Due to the saliency, the instantaneous torque contains a large ripple component. In the case of the test motor, the torque ripple was as much as 26% of the rated torque under sinusoidal current drive. The experiment showed that the ripple component could be reduced to 6% by superimposing a compensation current component on the current reference     

Control of synchronous reluctance machines

This work develops a comprehensive approach to the control of inverter-fed synchronous reluctance machines (SYNCREL), based on the machine's ideal model. From the theory a control simulation is designed. Simulation and experimental results are presented. The effects of saturation and iron losses are briefly considered     

Performance evaluation of axially-laminated anisotropic (ALA) rotorreluctance synchronous motors

Axially laminated anisotropic (ALA) rotor reluctance synchronous motors (RSMs) for use in variable speed drives, have a very high ratio of L_d/L_q and high L_d-L_q values, and do not carry rotor current. Consequently, an ALA rotor RSM has a high torque density, power factor, and efficiency, and its vector control is fairly simple. This paper presents an approach to the performance analysis of RSM and the test results on a prototype ALA-rotor RSM. The theory is based on the machine parameter determination by field computation via analytical and finite element methods. Design criteria derived from theoretical analysis and the nature of the magnetic field obtained from finite element analysis for the ALA-rotor RSM are presented. Test results on a prototype are presented to validate the theoretical calculations and to demonstrate the high performance of the ALA-rotor RSM. The high L_d/L_q ratio of 16 under rated magnetic saturation conditions, high power factor of 0.91, and above 84% efficiency are obtained for a 2-pole, 2 HP laboratory ALA-rotor RSM     

Sensorless-control of the synchronous reluctance motor

In this paper a sensorless closed-loop speed control for the synchronous reluctance motor is presented. The sensorless control is based on the torque vector control algorithm. It has been implemented using a high-speed digital processor DSP96002. Experimental results for a 120 W axially-laminated synchronous reluctance motor are presented and compared with operation with a speed sensor and simulations. A base speed range of 400-1500 RPM has been achieved. The top speed was extended to 2750 RPM using flux-weakening. The drive can be applied a full-load step-change within this speed range without losing synchronism     

Design of a synchronous reluctance motor drive

A segmental-rotor synchronous reluctance motor is used in a variable-speed drive with current-regulated pulse-width-modulated (PWM) control. The low-speed torque capability is compared with that of an induction motor, a switched reluctance motor, and a brushless DC PM motor of identical size and copper weight. A particular point of interest is the comparison of motors of different types, all with essentially the same frame size and tested under identical conditions. The results suggest that many of the desirable properties of the switched reluctance motor can be realized with the synchronous reluctance motor but with using standard AC motor and control components. The torque capability is lower, but so is the noise level     

Identification of linear synchronous reluctance motor parameters

This paper deals with experimental methods for the identification of linear synchronous reluctance motor (LSRM) parameters. A magnetically nonlinear two-axis dynamic LSRM model is derived. This model accounts for the effects of slotting, saturation, cross-saturation, and the end effects. The parameters of the obtained model are not constant. They are given by the characteristics of the flux linkages, thrust, and friction force depending on the mover position and the direct (d) and quadrature (q) axis currents. These characteristics are determined experimentally by a controlled voltage-source inverter employing closed-loop current control in the d-q reference frame. The proposed model, experimental methods, and determined characteristics are confirmed through a comparison between the measured and calculated results. Two tests are performed: a test at the locked mover, and kinematic control at low speed. The effects of cross saturation under dynamic operating conditions and the effects of slotting can be clearly seen in the measured and calculated results.     

Synchronous versus induction motors: plant efficiency benefits resulting from the use of synchronous motors

Induction motors are often the choice for various industrial production processes. Use of an induction motor, however, will result in increased lagging power-factor burdens in the plant. This burden often must be corrected by adding capacitors. If not, the result is the penalty of larger kilovoltampere burdens to the interconnected system. The synchronous machine, with the aid of an intelligent excitation controller, can control power factor to reduce the plant reactive loading to the connected system. This article discusses the application of the synchronous motor at the Lion Oil refinery and the digital excitation system used to control the machine power factor.     

Sensorless control of synchronous reluctance motors using on‐line parameter identification method not affected by position estimation accuracy

This paper presents a novel on‐line parameter identification method for sensorless control of Synchronous Reluctance Motors (SynRMs). Although conventional sensorless control methods based on mathematical models usually need some complex measurements of motor parameters in advance, the proposed identification method does not require them and can be realized on‐line. The proposed method identifies motor parameters under sensorless control, so rotor position and velocity cannot be used to identify these parameters. However, the proposed method does not need rotor position and velocity, and identified parameters are not affected by these estimation errors. The sensorless control using identified motor parameters is realized, and the effectiveness of the proposed method is verified by experimental results. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 62–69, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20258     

Analysis of permanent magnet synchronous motors

A detailed representation of buried permanent magnet synchronous motors at steady state is presented. An equivalent circuit is proposed that accounts for the saliency of the machine and for the particular influence of iron core losses on the machine operations. Both no-load and loaded conditions are analyzed and experimentally tested in order to describe the influence of the armature current on the rotor flux distribution. Experimental tests on a 2 HP buried permanent magnet machine are presented to validate the proposed approach     

无轴承开关磁阻电机径向电磁力模型

针对现有无轴承开关磁阻电机数学模型忽略磁饱和或对磁饱和考虑不充分的不足,将麦克斯韦张量法和磁路分析法结合起来,提出了一种计算无轴承开关磁阻电机径向电磁力的方法.该方法考虑了电机运行过程中磁饱和以及转子的偏心位移,能够准确的描述电机径向电磁力的特性,为电机运行状态的离线分析和电机的设计提供了更为可靠的理论依据;该模型同时为无轴承开关磁阻电机电磁振动和噪声的预测与控制提供了理论依据.以一台实验样机为例,建立了考虑磁饱和的无轴承开关磁电机有限元分析模型.仿真结果证明了该解析模型的有效性.