Shukang Cheng

Research on the Magnetic Characteristic of a Novel Transverse-Flux PM Linear Machine Used for Free-Piston Energy Converter

Free-piston energy converter, composed of a free-piston engine and a permanent-magnet (PM) linear machine, is a promising generator concept for series hybrid electric vehicles (HEVs). In this paper, a novel transverse-flux PM linear machine is investigated for such applications. Unlike conventional transverse-flux machines, the proposed machine features simple mechanical structure. Flux leakage of the proposed machine is analyzed, and parameters of the machine are optimized by finite-element method (FEM). Compared with conventional flux configurations, such as radial flux, axial flux and Halbach, the proposed transverse-flux topology showed advantages in low cogging force, low thrust fluctuation, and high efficiency. A prototype was designed and manufactured. Further experiments indicated satisfactory load characteristic of the machine.

Analysis of modulation pattern and losses in inverter for PMSM drives

Voltage source inverter is widely used in adjustable speed system for permanent magnet synchronous motor (PMSM). The modulation pattern and the power switching devices losses calculation in the inverter directly affect the performance of the entire system. Sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) techniques used in the inverter are introduced; the relationships between the two patterns are discussed. The power switching devices losses are analyzed and compared between the two modulation strategies-SPWM and SVPWM. A PMSM controller is carried out and an experimental bench is developed. The conclusions should benefit the prediction and further investigations of the system efficiency, the losses study and inverterpsilas heat sinking system.

Simulation of PMSG wind turbine system with sensor-less control technology based on model reference adaptive system

Model reference adaptive system(MRAS) is introduced in speed estimation for salient pole permanent magnet generator(PMSG) in wind turbine system. Firstly, current model for the salient pole PMSG is established and used as adjustable model, and the salient pole PMSG itself is used as reference model, then the adaptive law is derived. The estimated speed is used for the control of PMSG wind turbine system with full power back to back PWM converters, and maximum wind power point tracking is achieved through the specified optimum torque of PMSG. Simulation model of wind turbine system is built to verify the sensor-less control technology, in which the PMSG uses finite element model. And the simulation results show that the MRAS sensor-less control strategy has a good performance with nonlinear magnetic field of PMSG fully considered.

Analytical Method for Iron Losses Reduction in Interior Permanent Magnet Synchronous Motor

Interior permanent magnet (PM) synchronous motors are widely used in electric vehicle, where limited space for motors is one of the most crucial challenges. This paper proposes an analytical design method to decrease iron losses, which saves much computation time compared with the parameter sweep method adopting finite-element analysis (FEA). The new method provides a design principle of the rotor, by which the harmonic magnetomotive force of the PM and the iron losses can be reduced significantly. This paper also takes the influence of the pole arc angle on iron loss reduction into consideration. The validity of the analytical technique is verified by 2-D FEA.

Magnet Shape Optimization of Surface-Mounted Permanent-Magnet Motors to Reduce Harmonic Iron Losses

Surface-mounted permanent-magnet (PM) synchronous motors are widely applied to electric vehicles, where iron losses reduction is a crucial target. This paper proposes a new method of PM shape optimization to reduce the harmonics of magnetic field and, hence, iron losses. The proposed method is based on the analytical calculation of magnetic field distribution with a non-uniform PM shape, which can save much computation time compared with the parameter sweep method. The validity of the method is verified by 2-D finite-element analysis.

Analysis and restrain strategy of cogging torque in double-stator permanent magnet brushless motor

As the double-stator motor has two stators, if no techniques are adopted in motor design, the cogging torque of the double-stator motor will increase one time compared to conventional motors, which will decrease the performances of the whole motor system. For the existence of two stators, if the method of the skewing of the stator slots or alternatively of the PMs is adopted to reduce the cogging torque, the motor structure will be more complex. The paper aims at the structure features of this motor, a two dimensional finite element analysis method is used to analyze the main element to influence the cogging torque. The influences of relative position angle of the two stators, the magnet arc length, the inner and outer airgap length, and the combination of different teeth and slots are discussed to restrain the cogging torque. The scheme of staggering two stators to half cycle of cogging torque is provided, and the tests of the prototypes are made to support it.

Equivalent stator slot model of temperature field for high torque-density permanent magnet synchronous in-wheel motors accounting for winding type

Purpose – For high torque-density permanent magnet synchronous in-wheel motor, service life and electromagnetic performance are related directly to winding temperature. The purpose of this paper is to investigate the equivalent stator slot model to calculate the temperature of winding accurately. Design/methodology/approach – This paper analyzes the the law of heat flux transfer in slot, which points the main influence factors of equivalent stator slot model. Thermal network model is used to investigate the drawbacks of conventional equivalent model. Based on the law of heat transfer in stator slot, a new layered winding model is put forward. According to winding type and property of impregnations, detailed method and equivalent principle of the new model are presented. The accuracy of this new method has been verified experimentally. Findings – An accurate equivalent stator slot model should be built according to the low of heat transfer. According to theory analysis, the drawbacks of conventional equiva...

Experimental Study of Compound-Structure Permanent-Magnet Synchronous Machine Used for HEVs

A compound-structure permanent-magnet synchronous machine (CS-PMSM) system used for hybrid electric vehicles (HEVs) enables the internal combustion engine (ICE) to operate at the optimum efficiency region independent of road conditions, thus decreasing emissions and fuel consumption. The key part CS-PMSM is a high integration of two electric machines. The connection ways of the CS-PMSM in the HEV system are discussed and the better connection way is selected based on power. Different topologies of the CS-PMSM are put forward and compared on criteria, such as magnetic coupling, power match, thermal properties, etc. A downsized axial-axial flux prototype machine was designed and manufactured for the testing facilities and concept validation. The performance, magnetic coupling, efficiency, and temperature of the axial-axial flux CS-PMSM prototype are measured and analyzed to provide a reference for this kind of machine.

Research on torque performance for permanent-magnet in-wheel motor

To improve the torque performance of wheel motor, a concentrated winding motor with 12-slot-10-pole, embedded magnets rotor structure is presented in this paper. The influence of motorpsilas parameters such as the PMpsilas magnetization orientation length, the winding turns and inner diameter of stator on output torque is discussed by using finite element method. The design method of increasing motor torque is given. To reduce torque ripple, the asymmetric arc method is used to optimize the rotor shape, the effect of the length of air-gap and the angle of rotor pole arc is discussed. An optimum design scheme of reducing torque ripple is proposed. The simulation results show that the output torque is achieved, the torque ripple is reduced and a suitable motor model is obtained.

Design and Simulation of a Self-Excited All-Air-Core and Fabrication of a Separate-Excited All-Iron-Core Passive Compulsator

This paper presents a detailed description of design and simulation of a self-excited all-air-core and fabrication of a separate-excited AU-iron-core compensated pulsed alternators (compulsator), also including the similarity and difference in configuration and principle of two prototypes. Presented are fabrication techniques, assembly processes and design methods developed specifically for pulsed power generators, including the carbon fiber rein-forced epoxy resin composite material usage of stator and rotor core in all-air-core compulsator, and the armature and field winding fabrication techniques and conglutination processes in All-iron-core compulsator. The armature winding is wound concentric winding by flat copper bars, the end-turn superposition problem solved by heating the flat copper bar to soften them for taking shape. Designs of a lightweight self-excited all-air-core rotating-field passive compulsator and a separate-excited AU-iron-core compulsator for comparison have been completed. They all have rotating-field, two-phase, four-pole, and slotless armature winding and passive compensation .The heart of the self-excited all-air-core passive compulsator is carbon fiber rein-forced epoxy resin composite rotor which rotates at 10000 rpm or more, and that epoxy composite resin stator reduces the saturation of the compulsator, which consequently reduces transient inductance of armature winding and increasing the magnitude of pulsed current. The usage of composite material also reduces the mass of the all-air-core compulsator and increases the velocity of the rotor and inertial energy storage, therefore increasing the energy density and power density. Another feature of the all-air-core PCPA is the use of two armature windings on the stator, which allows optimization of each armature winding to its specific duty cycle. Control of self-excited process is presented as well as the synchronous control of solid-state switch in excitation circuit and discharge main circuit by the special controller. The paper presents the simulation of magnetic field at no-load and discharge instance respectively. The paper analyzes the impact of the thickness of compensation shield to the performance of compulsator. Finally, the experiment schematic of all-air-core compulsator system is presented.