Torque improvement of five-phase surface-mounted permanent magnet machine using third-order harmonic
17 Jul 2016-pp 1-1
TL;DR: In this article, the authors presented the optimal value of third harmonic injected into the sinusoidal PM shape and current waveform for maximum torque improvement is analytically derived and validated by both finite element analyses and experiments.
Abstract: This paper presents optimal third harmonics in both permanent magnet (PM) shaping and current waveform to improve the output torque of five-phase surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape and current waveform for maximum torque improvement is analytically derived and validated by both finite element (FE) analyses and experiments. It is found that the optimal third harmonic is 1/6 of the fundamental one for both PM shape and current waveform. For the five-phase SPM machines having rotors without shaping, Sine shaping, or Sine shaping with third harmonic injected, the electromagnetic performance including the back EMF waveform, cogging torque, average torque, torque ripple, copper loss, iron loss, impact on power inverter, and demagnetization withstand capability are compared. It is demonstrated that, although the copper loss and iron loss increase due to additional third harmonic in the winding current and magnet shape, the average torque with optimal third harmonics injected in PM shaping and current waveform can be improved by >30% while the torque ripple and remains similar to that of the one with Sine shaping. In addition, this will reduce the dc bus voltage while maintaining the machine torque density. Furthermore, the machine with Sine and Sine+3rd rotors presents much better demagnetization withstand capability performance than conventional rotor.
Citations
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TL;DR: In this article, a novel design method of permanent magnet synchronous generator (PMSG) was proposed, where the volume of PM remains unchanged during the entire design procedure and the maximum output power scheme was found out just by optimizing the PM's shapes with the change of mechanical pole-arc coefficient.
Abstract: This paper puts forward a novel design method of permanent magnet synchronous generator (PMSG) The most significant advantage of this method is that the output power of PMSG can be prominently improved without increasing any material costs The main difference from the traditional design scheme is that the volume of permanent magnet (PM) remains unchanged during the entire design procedure And the maximum output power scheme is found out just by optimizing the PM's shapes with the change of mechanical pole-arc coefficient In other words, this method aims to obtain the maximum PM utilization design scheme that can produce more “effective” magnet field so that it can generate the larger output power The dimension parameters of PMs with different shapes are calculated by the equivalent analytic geometry method To verify its availability, this novel method is performed on four common types of PMSGs with different rotor structures, and their satisfactory performance results are obtained The comparison with the traditional machine design scheme is also presented to illustrate the innovation and priority The finite-element analysis method based on Ansoft/Maxwell is applied for the electromagnetic models’ building and simulation
29 citations
Cites background from "Torque improvement of five-phase su..."
...Besides reducing torque ripple, improving efficiency and widening operation range which are mentioned above, there are many other optimization goals for PM machine design, such as reducing iron loss [15], [16] as well as eddy current loss reduction [17]–[19] and improving average torque [20]....
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TL;DR: Two methods to derive an inverse model in harmonic forms for analyzing the interactions between the torque/current gains and currents, and for suppressing the torque ripples of a multiphase permanent magnet (PM) motor are presented.
Abstract: This paper presents two methods to derive an inverse model in harmonic forms for analyzing the interactions between the torque/current gains and currents, and for suppressing the torque ripples of a multiphase permanent magnet (PM) motor. The first method directly calculates the desired current harmonics from a pseudo-inverse model of a multiphase PM motor with no input-voltage saturation, which is independent of its rotor displacements, for torque ripple compensation. The second is an iterative-free method formulating the inverse model as an optimization problem that minimizes the copper loss subject to torque constraints while accounting for the effects of the input-voltage saturation. The formulation and significance of the two methods are illustrated with a multiphase PM motor for which published measurements are available for model validation and compared with three other commonly used current waveforms for benchmark comparison in terms of torque-ripples and copper losses.
25 citations
Cites methods from "Torque improvement of five-phase su..."
...Parametric investigations include the effects of PM shape [7]–[9] and arc [10], stator geometry [11], and slot/pole number combination [12] on torque ripples, where Scuiller [7] utilizes small trapezoid notches and [8] and [9] are based on harmonic injecting to optimize the PM shape to suppress the torque ripples....
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TL;DR: In this article, an optimization problem that aims to maximize the torque for given maximum peak voltage and root mean square (RMS) current is formulated: the optimal torque sharing among the two virtual machines (the two dq -axis subspaces) that represent the real five-phase machine is thus calculated for any mechanical speed.
Abstract: In this paper, the study of the torque and power versus speed characteristics for a family of five-phase surface-mounted permanent magnet machine is carried out. With considering hypotheses [linear magnetic modeling, only first and third harmonic terms in the back electromotive force (EMF) and current spectrums], an optimization problem that aims to maximize the torque for given maximum peak voltage and root mean square (RMS) current is formulated: the optimal torque sharing among the two virtual machines (the two dq -axis subspaces) that represent the real five-phase machine is thus calculated for any mechanical speed. For an inverter and a dc voltage sized with only considering the first harmonic of back EMF and current, the problem is solved with changing the virtual machine back EMFs and inductances ratios. With the introduction of the maximum torque/speed point, maximum power/speed point, and maximum reachable speed, it can be shown that, if the inductance ratio is large enough for given Volt–Ampere rating, the machine can produce higher torque without reducing its speed range, thus meaning that the capability of the inverter to work is improved with the use of the third harmonic. This property is all the truer as the base armature reaction is large. A particular five-phase machine is sized and numerically analyzed to check this property.
25 citations
Cites background from "Torque improvement of five-phase su..."
...The inductance ratio is mainly determined by the winding distribution and the slot shape whereas the no load back EMF mainly depends on the winding distribution and magnet layer properties (magnet shape, magnetization orientation): for a given winding, it is then theoretically possible to design a magnet layer to obtain the wanted back EMF ratio [18]–[20]....
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...As the spatial third harmonic components result from the PM implementation [18], [19] but also from the winding [20], the chosen macroscopic elements for the study are the inductances and the EMFs....
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...In practical terms, with the proposed approach, the designer can predict the change in the Torque/Speed characteristic when acting on the winding distribution and the magnet layer design (bearing in mind that the impacts on the torque quality is analysed in [18] for example)....
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TL;DR: In this article, the design of a particular double-polarity (DP) five-phase machine is presented. And the performance of the prototype with a fractional-slot concentrated winding of 40 slots and 16/48 poles is compared with the equivalent no-fault-tolerant three-phase 24 slots/16 poles machines.
Abstract: In the context of traction drives with required torque transient capabilities and a classically wide flux weakening speed range, this paper gives design considerations of a particular double-polarity (DP) five-phase machine. Beyond its intrinsic fault tolerance due to its five phases, its specificity is the ability to develop torques of comparable values under three kinds of supply: with only first, third or both first, and third sinusoidal currents. This property, due to first $(E_{1})$ and third $(E_{3})$ harmonic electromotive forces of comparable values, gives more degrees of freedom for the control of the machine. Unlike three-phase sinusoidal machine, flux weakening is no more the unique solution when maximum voltage is reached. Thanks to the extra degrees of freedom in this kind of machines, more possibilities for the control of the torque and current supply can be applied. At first, elements for the choice of slots/poles combination of such DP machines are given. Then, in the case of an interior permanent magnet synchronous machine, possible adaptations of the rotor are proposed in order to bring the double p/3p polarity property. The last design criterion considered is the level of eddy-current losses, important at high frequencies. For the proof of the concept effectiveness, a prototype with a five-phase fractional-slot concentrated winding of 40 slots and 16/48 poles is presented with results from the experimental setup and finite element modeling. A comparison with the equivalent no-fault-tolerant three-phase 24 slots/16 poles machines is also carried out.
24 citations
Cites background or methods from "Torque improvement of five-phase su..."
...pole machine in [9] with a conventional rotor structure, the torque improvement is equal to 1....
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...In these two papers [8], [9], the (ξw )3 winding factor for the third harmonic is weak (less than 0....
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...However, Gopt is obtained here with the same RMS current but not the same peak current as in [9]....
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...In [9], a 10-slot/8-pole SPMSM with a PM shaping technique in accordance with harmonic current injection ratio is investigated....
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TL;DR: It is found that the incremental output torque decreases with the order of the harmonics, but the output torque does not increase when the harmonic order is higher than seventh and the average torque with the optimal harmonics can be enhanced while the torque ripple remains similar to that of the one with the sinusoidal field rotor.
Abstract: The harmonics can be utilized in the outer frame of a permanent magnet and phase current waveform in a multiphase machine to improve the output torque capability. The relationship between the output torque and harmonics in both the shape of the permanent magnet and phase current waveform is mathematically established in this paper. Consequently, the optimum harmonics are quantitatively identified and verified by the finite-element (FE) method. It is found that the incremental output torque decreases with the order of the harmonics. However, the output torque does not increase when the harmonic order is higher than seventh. It is also shown that the harmonics in the shape of the permanent magnet and phase current waveform influenced each other. The optimum of the interacted harmonics is dependent on the fundamental and harmonic winding factors. For the dual three-phase surface-mounted permanent magnet (SPM) machines with tile rotors, sinusoidal field rotor, and sinusoidal with third harmonic field rotor, their airgap flux density, back electromotive forces, and torque characteristics are compared. It is demonstrated that the average torque with the optimal harmonics into both the shape of the permanent magnet and phase current waveforms can be enhanced while the torque ripple remains similar to that of the one with the sinusoidal field rotor. Finally, the prototype machine is built and measured to verify the analytical and FE analysis.
20 citations
Cites background from "Torque improvement of five-phase su..."
...However, previous published work on it has been focused on the threephase and five-phase machines to enhance the output torque [14]–[18], while little literature studies the influence of the higher harmonics utilization and their optimal ratio on the outer frame of the PM....
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References
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TL;DR: An attempt is made to provide a brief review of the current state of the art in the area of variable-speed drives, addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphases machine designs.
Abstract: Although the concept of variable-speed drives, based on utilization of multiphase machines, dates back to the late 1960s, it was not until the mid- to late 1990s that multiphase drives became serious contenders for various applications. These include electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, ldquomore-electricrdquo aircraft, and high-power industrial applications. As a consequence, there has been a substantial increase in the interest for such drive systems worldwide, resulting in a huge volume of work published during the last ten years. An attempt is made in this paper to provide a brief review of the current state of the art in the area. After addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphase machine designs, various control schemes are surveyed. This is followed by a discussion of the multiphase voltage source inverter control. Various possibilities for the use of additional degrees of freedom that exist in multiphase machines are further elaborated. Finally, multiphase machine applications in electric energy generation are addressed.
1,683 citations
TL;DR: A detailed overview of the state-of-the-art in multiphase variable-speed motor drives can be found in this article, where the authors provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as the approaches to the design of fault tolerant strategies for post-fault drive operation.
Abstract: The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operation.
1,445 citations
TL;DR: A wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives are reviewed.
Abstract: Permanent magnet AC (PMAC) motor drives are finding expanded use in high-performance applications where torque smoothness is essential. This paper reviews a wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives. Sinusoidal PMAC drives generally show the greatest potential for pulsating torque minimization using well-known motor design techniques such as skewing and fractional slot pitch windings. In contrast, trapezoidal PMAC drives pose more difficult trade-offs in both the motor and controller design which may require compromises in drive simplicity: and cost to improve torque smoothness. Controller-based techniques for minimizing pulsating torque typically involve the use of active cancellation algorithms which depend on either accurate tuning or adaptive control schemes for effectiveness. In the end, successful suppression of pulsating torque ultimately relies on an orchestrated systems approach to all aspects of the PMAC machine and controller design which often requires a carefully selected combination of minimization techniques.
978 citations
"Torque improvement of five-phase su..." refers methods in this paper
...In order to remain low torque ripple, several techniques based on the optimization of machine parameters can be employed [5]....
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TL;DR: In this article, a five-phase brushless permanent magnet motor with concentrated windings has been proposed, where the produced back electromotive force is almost trapezoidal and the motor is supplied with the combined sinusoidal plus third harmonic of currents.
Abstract: A five-phase brushless permanent-magnet (PM) motor is introduced. The proposed motor has concentrated windings such that the produced back electromotive force is almost trapezoidal. The motor is supplied with the combined sinusoidal plus third harmonic of currents. This motor, while generating the same average torque as an equivalent PM brushless dc motor (BLDC), overcomes its disadvantages. The motor equations are obtained in the d/sub 1/q/sub 1/d/sub 3/q/sub 3/0 rotating reference frame. Therefore, the so-called vector control is easily applicable to this kind of motors and the motor has the same controllability as a PM synchronous motor (PMSM). For presenting the superior performance of the proposed five-phase motor, its three and five-phase PMSM and BLDC counterparts are also analyzed. Finite element method is used for studying the flux density and calculating the developed static torque. Also, the developed torque is obtained using the mathematical model in the d-q reference frame. The average torque and the torque ripple for all cases are calculated and compared. Experimental results are in good agreement with the simulation results.
428 citations
"Torque improvement of five-phase su..." refers background in this paper
...However, the torque density is reduced and this can be compensated by utilizing third harmonic into the PMs shapes [17]– [22]....
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...Alternatively, in multiphase machines, the third-harmonic current, which interacts with the third-harmonic EMFs, was injected into the winding to improve the output torque capability [22]–[27]....
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...Although the principle of third-harmonic current injection has been discussed in [22]–[27] and most of the literature focuses on the injecting current on the torque improvement, little literature has been presented relating to determination of windings, PM shapes or third-harmonic current injection ratio....
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TL;DR: In this article, a measure of third harmonic to the output of each phase of a three-phase inverter was proposed to obtain a line-to-line output voltage that is 15 percent greater than that obtainable when pure sinusoidal modulation is employed.
Abstract: By adding a measure of third harmonic to the output of each phase of a three-phase inverter, it is possible to obtain a line-to-line output voltage that is 15 percent greater than that obtainable when pure sinusoidal modulation is employed. The line-to-line voltage is undistorted. The method permits the inverter to deliver an output voltage approximately equal to the voltage of the ac supply to the inverter. Thus an induction motor of standard rating with respect to the ac supply to the inverter can deliver very nearly full power at rated speed when supplied from the inverter. This is achieved without pulse dropping or any other form of mode-changing.
383 citations