A Novel Sensorless-Drive Method to SRM by Impressing Pulse-Voltage on a Single Phase 1
A Novel Sensorless-Drive Method to SRM by
Impressing Pulse-Voltage on a Single Phase
Due to a lot of drawbacks exist at present in the sensorless drive methods of Switched Reluctance Motor (SRM)-; a new conception is proposed in this paper. The feature of the proposal is: only one unexcited phase is required to be impressed pulse voltage for detecting the rotor position. Consequently, both of the control circuit and algorithm are simplified. Furthermore, since the mechanism for determining the impressed timing of the pulse voltages is introduced into the control system, the negative torque and noise resulting from the residual currents can be extremely eliminated. In addition, for the sake of the proposed method is quite simple, instead of expensive Digital Signal Processor (DPS) the entire experimental system can be implemented by Field Programmable Gate Array (FPGA). The appropriateness and efficiency of the proposed method are confirmed through the comparison of those results from simulation studies and experiments.
Keywords: Switched Reluctance Motor, Sensorless Drive, Pulse Voltage, and FPGA.
為改善目前存在於切換式磁阻馬達無檢測器驅動法之缺點(對此(本文提出一個新的方法(來解決這些問題。 此法的特點為: 一，只要單一非激磁相印加以脈衝電壓即可檢測出轉子位置。因此(在硬體設備及控制程式上都可以被簡化。二，導入脈衝電壓印加時機的決策機構。如此一來(因殘存電流所導致之負轉矩可被精確地去除(所以馬達運轉穩定且噪音減小。又所提案之驅動法相當地簡單(故可利用FPGA以取代昂貴的DSP來完成。最後(本文將所提方法進行電腦模擬(並與實機試驗作比較(以驗證該方法之可行性與有效性。
投稿受理時間: 92 年 10 月 15 日 審查通過時間: 93 年 1 月 2 日
Nowadays, owing to the remarkable growth I. Introduction
of power electronic technology, various subjects
to AC motors have been progressed. Where, the In the recent years, the rapid industriali-
application of SRM is worthy of note. Since the zation makes the demand on automatic
framework of SRM is only built of silicon-steel production equipment increase. Where, electric
laminations in both rotor and stator, it is not only motors have been taken as the main drivers to
quite simple in structure but also solidly enough those production facilities. In order to further
to operate in high speed driving and the serious extend the application of electric motors, the
environments with high temperature or vibration. improvement of motor performance is strongly
Furthermore, for the reason of no winding loss desired. However, since the problems as brush
occurring in rotor as it existing in permanent discharge and commutator sparks involving with
magnet synchronous motors (PMSM), the the unavoidable abrasion between brushes and
efficiency of SRM is better than those of commutator to DC motor occur frequently, the
induction motors. According to those desirable conservative periodical inspection is required.
features and advance performance of SRM as Consequently, the growing tendency toward the
simple structure, high reliability and low cost, it substitution of AC motors for the DC ones to
is adoptable to be the low-cost variable-speed solve the problems.
drivers in many industrial applications as Since the proposed method is quite simple, changeable speed motors, starters of aircraft, the experimental system can be implemented by hydraulic pumps, fans, blowers and the driving instead of the expensive DSP to a simple analog starters of scooters, electric mobiles etc.. and digital circuit as FPGA. The appropriateness
A Novel Sensorless-Drive Method to SRM by Impressing Pulse-Voltage on a Single Phase 3 However, SRM has not been put into and efficiency of the proposed method are practical applications widely for the problems of confirmed through the comparison of those large torque ripple, acoustic noise and low results from simulation studies and experiments. power factor. In addition, since most of
conventional position sensors for SRM drive are II. Estimation of Rotor Position
& Determination of Exciting weak in structure, it is damageable in high
Timing temperature, noise or vibration environments.
That is, the applications of SRM are constrained.
A. The Nature of SRM Until now, the methods of driving SRM by
sensorless control have been variously proposed -, but above studies are still far from stator practical application. In this paper, a simple and
rotor practical method to improve the drawbacks of
those sensorless drive methods by the
Positive Negative conception of impressing pulse voltage is Torque Torque inductance proposed. Here, two key contributions will be
1. Instead of impressing pulse voltage into all Rotor Position θ [deg.] rotor position phases of SRM, there is only one unexcited
Fig.1. Correlation of Rotor Position and phase required. This conception much
Variation Inductance simplifies the control circuits and algorithm.
2. A new mechanism is introduced into the The torque generation of SRM bases on the control system to determine the exciting reluctance characteristic as well as the one of a timing of pulse voltage. By which, the conventional motor which can be expressed by negative torques and noise resulting from the rotor position θ and magnetic energy W. residual currents of inductive windings can be ，W (1) T；，，completely eliminated.
In addition, if the nonlinear characteristic of pulse voltages must be hold until the excitation magnetic material is neglected , the magnetic to driven phase completely (the slop of energy can be future expressed as: inductance is positive). Consequently, for the accurately impressing pulse voltages on all 4 臺北科技大學學報第三十七之一期 phases, it makes the control system of sensorless
drive be complicated. Moreover, since the value 12 (2) W；L(，)iof residual current is larger, the current 2
corresponding to pulse voltage is easy to be Through the combination of (1) and (2), the
vanished. It will cause the serious error in correlation between magnetic torque and space
calculation of impressing timing. distribution of inductance can be obtained. For the improvement of above drawbacks ，1，()L2exiting in conventional methods, the sensorless (3) ；Tidrive of SRM based on i