H. N. Phyu

Influence of winding structure and the effect of MMF harmonics to the spindle motor performance for ultra-high TPI HDD

The technologies for maintaining high recording density to suppress mechanical vibration and media flutter for ultrahigh TPI hard disk drive (HDD) require advance spindle motor design and technology against the traditional norms. To realize multimagnetic poles with limited stator slots, spindle motors generally use concentrated windings which offer small end winding and simple structure suitable for mass production. There is a variety of ways to construct a motor with different winding structures based on different pole/slot combinations. Winding structures directly affect the producing of motor back-emf and torque which determine motor capacity, reliability and efficiency. In this work, detailed analysis is carried out to identify the optimal winding structures of the high speed spindle motor and analyze their effect on the motor performances by using magneto-motive force harmonics analysis and electromagnetic magnetic field analysis. Results are useful in preliminary and final optimal designs of the high speed spindle motors.The technologies for maintaining high recording densities to suppress mechanical vibration and media flutter require advance spindle motor design and technology. To realize multi-magnetic poles with limited stator slots, radial air gap field HDD spindle motor are normally used concentrated winding. Based on different pole/slots combinations, there would be a variety of winding configurations. In this work, detailed analysis is carried out to identify the optimal winding structures of the high speed spindle motor and analyze their effect to the motor performances by using MMF harmonics analysis and FEM. Results are useful in preliminary and final optimal designs of the high speed spindle motors.

Unbalanced magnetic pull induced by leading wires of permanent magnet synchronous motor

The leading wires of the armature winding may conduce the windings be asymmetric in permanent magnet synchronous motor (PMSM), and finally induce an additional unbalanced magnetic pull (UMP) in the motor operation. The influence of the UMP could be serious, especially in the operation of high speed PMSMs. The paper analyzes the reason inducing this special UMP, and effects of UMP to the motor operation. Several measures also proposed for weakening the influence of the UMP.

Influence of Drive Current to Unbalanced-Magnetic-Pull in Spindle Motor

Both symmetric and asymmetric armature windings are applied in the spindle motors used in hard disk drives. Consider the influence of the drive current in the windings, the analysis to the unbalanced-magnetic-pull (UMP) generated in the motor becomes more difficult. Besides the intrinsic and extrinsic components, the additional UMP can also induced by the current, and the UMP could thus be serious. This paper analyzes this phenomenon, and presents a model which can describe clearly the influence of the drive current to the UMP. For verifying the effectiveness of the analytic method proposed, several spindle motors are analyzed, and compared with the results obtained by using FE method. The comparing proves the effectiveness of the UMP model presented.

Analysis of Three Synchronous Drive Modes for the Starting Performance of Spindle Motors

In sensorless operation of spindle motors in hard disk drives (HDD), open-looped starting is used to spin up the motor from standstill to a speed that is high enough to reliably detect back-electromotive force (back-EMF) generated in the armature windings. Then the back-EMF zero-crossing points (ZCP) will be used to detect speed and position for closed-looped control. This paper studies three open-looped starting modes for spindle motor. Six-step, which is currently used in HDD, twelve-step, and sine wave starting are illustrated and compared. The simulation results show that twelve-step and sine wave starting can obtain much better starting performance for spindle motors.

Influence of Neutral Line to the Optimal Drive Current of PMAC Motors

The optimal drive current can reduce both the torque ripple and power loss in driving the permanent magnetic (PM) AC motor. This paper presents an analytical model for calculating the optimal drive current of the PMAC motor with surface mount PM rotor. Both the motors with and without the neutral line are analyzed. Theoretical analysis shows that, when the back-emf of the windings contains triple order harmonics, the neutral line of the motor can let the optimal drive current be different from the one without the neutral line, and it can also make the optimal drive current be more effective in the loss and torque ripple reduction. Two spindle motors are used in the analysis to show the influences of the optimal model presented.

Influence of magnetization model to the performance of spindle motor

Analysis shows that, the influence of permanent magnet (PM) magnetization model can affect the performance of the spindle motor obviously, especial for the motor with high energy-product PMs. In the paper, different PM magnetization models are analyzed and their effects to the spindle motor performances are investigated. Field-circuit-motion coupled Time-stepping finite element method (FEM) is used to evaluate the effect of different PM magnetization fields with non-linear characteristic. Results discloses that the magnetization orientation of the permanent magnet can affect directly the efficiency and electromagnetic (EM) torque of the motor. Preliminary investigation of the effect of PM excitation is vital to optimize the motor performances, especially in early design stage. All these are important to realize the spindle motor with high efficiency, low acoustic noise, and high power density.

Analysis of rotor eddy current loss with different magnetization directions in PM BLDC motor

This paper presents the analysis of rotor eddy current loss with different permanent magnet magnetization directions in high speed permanent magnet brushless DC (PM BLDC) motor. Transient analysis is performed by time stepping finite element method which takes into account the induced eddy current, non-linearity, non-sinusoidal field and material saturation; which are very difficult to include in traditional analytical methods. Promising results can apply in motor performances optimization especially in reduction of rotor eddy current loss and optimal motor design.

Numerical Modeling and Performance Analysis of a Disk Drive Spindle Motor using Circuit-Field Coupled Systems

This paper presents the modeling, simulation and performance analysis of the disk drive spindle motor using numerical methods. Dynamic model of the motor is developed using time stepping FEM. Due to the direct coupling of the transient electromagnetic field, circuit and motion; the solutions can take into account the saturation effect, the eddy current effect, the rotor movement, the non-sinusoidal quantities and high order harmonics of the electromagnetic field which are very difficult to include in analytical approach and traditional FEM. An improved steady state model is proposed using time stepping FEM combined with magneto-static FEM to reduce the time spent in reaching steady state solution. A new approach to couple the time stepping FEM with closed loop feedback control is presented to analyze the motor with a controller as an actual motor-controller drive system