Motor Starter Comparison

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Proceedings of the International MultiConference of Engineers and Computer Scientists 2009 Vol II IMECS 2009, March 18 - 20, 2009, Hong Kong

Comparison between Direct-On-Line, Star-Delta and Auto-transformer Induction Motor Starting Method in terms of Power Quality H.H. Goh, M.S. Looi, and B.C. Kok
Abstract—This paper presents a comparison between the Direct-On-Line (D.O.L.), Star-Delta, and Auto-transformer induction motor starting method in terms of power quality. The purpose of this research is to find out the most reliable and practical starting method which has the less power quality problems. These three basic starting methods which differ in their respective wiring connection are the most applicable and widely-used starting method in the industrial area due to its economic reasons. This research is done by analyzing the existed power quality events during the motor starting by using the Fluke Power Quality Analyzer to capture the waveforms of the events. After the experiments, the three different starting method are being compared to conclude the most suitable and applicable starting method which causes the least severe power quality events. Index Terms— Autotransformer, D.O.L., Power quality, Star-Delta.

II. RESEARCH BACKGROUND Power Quality [3] is an issue between the compatibility of the supply systems and the loads. Probably the most widely recognized and studied effect of motor starting is the voltage dip that is experienced throughout an industrial power system as the direct result of starting large motors [4]. There are several general methods of starting induction motors: full voltage, reduced voltage, wye-delta, and part winding types. The reduced voltage type can include solid state starters, adjustable frequency drives, and autotransformers [5]. Motor starting has been investigated for decades [5-16]. The most frequent power quality events that occur are voltage sags and voltage transients as well as harmonics. Generally, voltage sags occur due to short-circuit faults, however, motor starting is also the main cause of the voltage sags. The starting of industrial-range motors draw a larger current than normal, typically ten times higher than usual, remains until the motor reaches in nominal speed, which takes several seconds to minutes. Evaluating these concerns requires measurement equipment that can capture the voltage sags waveforms over the full duration. The power quality analyzer/meter as well as other tools such as software implementation are need to monitor through the significant events even in just a few milliseconds of time, because the voltage sags is enough to trip a fuse, blinking the lighting systems or even disrupt sensitive equipment. A thorough and detail study of the motor starting should be carried out to identify the voltage sags and their characteristics respectively. III. VOLTAGE SAGS IN MOTOR STARTING Power quality events such as voltage sags and harmonics may occur in motor starting due to the inrush current. Inrush current occurs because the motor will draw six to ten times of current than usual to produce a starting torque. Voltage sags due to the starting of large motors can again be theoretically calculated similar to the one caused by system faults [17].

I. INTRODUCTION

T

HE rapid technological progression in these days, both of the electric utilities and end users of electric power are becoming increasingly concerned about the quality of electric power. The increasing emphasis on overall power system efficiency has resulted in continued growth application of devices such as high-efficiency, adjustable-speed motor drives and shunt capacitors for power factor correction to reduce losses. This causes the increases in harmonic levels on power systems and has many people concerned about the future impact on system capabilities [1]. The starting of large motors and their associated loads has always presented an electrical and equipment challenge [2]. The main reason...
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