Zou Jibin

Finite element calculation of the saturation DQ-axes inductance for a direct drive PM synchronous motor considering cross-magnetization

Direct-drive torque-servo permanent magnet synchronous motor often operates in overload conditions. Its characteristic is evidently influenced by magnetic circuit saturation. The direct-axis and quadrature-axis inductances of surface mounted permanent magnet synchronous motor are usually considered as constant i.e. L/sub d/=L/sub q/. In fact, both the d-axis and q-axis inductances vary with load condition because of magnetic circuit saturation. A novel procedure is developed to calculate the dq-axes inductance with saturation by finite element method considering cross magnetization. Through magnetic field computation, the influence of saturation and cross-magnetization on dq-axes inductance is further investigated.

Numerical calculations for ferrofluid seals

The magnetic field and the seal capacity of ferrofluid seals are calculated and analyzed by numerical methods. Based on the magnetic filed calculations, the isobars in the ferrofluid and the cross sections of the fluid sealing ring are described. The relations of the seal capacity to the ferrofluid amount and the magnetic circuit parameters are analyzed. The action of the centrifugal force on the seal is indicated. >

Numerical Analysis on the Magnetic Field of Hybrid Exciting Synchronous Generator

A hybrid exciting synchronous generator (HESG) is analyzed in this paper, including its particular structure and operation principle. A permanent magnet generator is used for providing the main output and a homopolar inductor alternator is used for regulating the terminal voltage. The electromagnetic field computation and the performance analysis of the HESG are carried out by using three-dimensional finite element method. A 1.5 KW, 2000 rpm to 9000 rpm, 8-pole and 9-slot HESG is tested to verify the flux control capability. Experimental results show that it is possible to obtain a voltage from 64% to 126% of the voltage generated only by PM with the adjustment of the exciting current. And the variation range of the output voltage can be narrowed greatly while the speed of the generator varies from 2000 mm to 9000 rpm.

Error analysis and compensation of multipole resolvers

The signal errors of the multipole resolver and the measurement error incurred due to the signal errors are analysed, and expressions for the errors are determined. Based on the results of the analysis, a compensation method utilizing an analogue circuit for the measurement error is presented. The zero-position error and the amplitude error of the 34-pole resolver are compensated using the compensation circuit presented. The measurement accuracy of the 34-pole resolver is improved significantly from about 15 to 2 min. The correctness of the analysis result and the effectiveness of the compensation method are also verified.

The Design of an Effective Marine Inertial Navigation System Scheme

Accuracy of marine inertial navigation system (INS) is mainly dominated by gyroscope. In this paper, a new scheme (inertial gyrocompass system) is designed to realize high accuracy INS on the basis of low accuracy float gyros and velocity information of Doppler log. By choosing optimal 2-order horizontal damping network and 1-order azimuth damping network and designing logical damping parameter, the positioning error caused by gyro drift can be eliminated to a large extent. Computer simulation and experimentations show this scheme is effective and practicable.

Design and pressure control of high pressure differential magnetic fluid seals

In this paper, the design methods and pressure control for this kind of magnetic fluid seal are presented and a seal device is designed and tested.

DSP based all-digital resolver-to-digital conversion using DSRF-PLL

Nowadays all-digital resolver-to-digital conversion is popularly invested for space-limited applications. However time delay is inevitable in demodulation part when frequency shifting algorithm used. Furthermore, the angle calculation result is affected by time delay. So the synchronous demodulation is analyzed in this paper to void time delay. The demodulated sine and cosine signals always exist with amplitude and quadrature errors. In order to eliminate the influence of these two errors, the double synchronous reference frame-based phase-locked loop (DSRF-PLL) is investigated in the angle calculation part. DSRF-PLL removes the angular position error caused by the amplitude error and makes the position error caused by the quadrature error to be a constant value, which can be easily compensated in the software. So the angular position can be detected with no time delay and error. The presented all-digital resolver-to-digital conversion scheme is verified by the simulation and experimental results at the end of this paper.

Design and analysis of a novel Hybrid Excitation Synchronous Generator

A Hybrid Excitation Synchronous Generator (HESG) with a simpler configuration is described in detail. The Finite Element Method is used for the calculation and analysis on unload excitation field. An experiment for output voltage control is turned out to be coincident well with those of FEM. Those conclusions strongly show that the flux of HESG can be easily adjusted in a wide range and the steady-state control of output voltage can be realized by adjusting the exciting current. This is beneficial in building the foundation theory of HESG analysis as well as for direct design and experimental works.

Thermal analysis of underwater oil-filled BLDC motor

The viscous fluid in the air gap of underwater oil-filled Brushless Direct Current (BLDC) motor introduces an additional loss component and on the other hand improves the heat transfer between the rotor and stator. Based on the heat transfer characteristic of underwater oil-filled BLDC motor, thermal analysis of the motor considering the convection of the oil in the air gap is performed by two-dimensional finite element method (FEM). The agreement between the calculation results and test results verifies the effectiveness of the computation.

Quantitatively evaluation on the cogging torque of permanent magnet motor caused by stator and rotor defect

Cogging torque makes great attribute to the torque ripple and noise of permanent magnet motor. The causes to produce cogging torque are discussed in this paper. The cogging torques of two PM motors is computed by finite element analysis. Computed results show the effectiveness of pole-slot-pairing method to reduce ideal cogging torque. While in practical motor, there may be some defects caused by manufacture, such as magnet performance discrete, and the evaluation of stator inner surface. These defects can cause non-ideal cogging torque. Such cogging torque is quantificationally analyzed by finite element analysis.