Adjustable Speed Drives Response to Voltage Sags Surya Hardi 1,a , Muhd. Hafizi 1,b , and Rohana Ismail 2,c 1 Center of Excellence Renewable Energy, School of Electrical System Engineering UniMAP, Malaysia. 2 Universitas Muhamadyah Sumatra Utara (UMSU), Indonesia a surya@unimap.edu.my, b hafiziidris@unimap.edu.my, c rohana0511@yahoo.com Keywords: Voltage sags, adjustable speed drives, diode rectifier current, and sensitivity. Abstract. This paper presents a study to investigate response of adjustable speed drives due to voltage sags. A small ASD of 0.39 kW, 50/60 Hz, and 400-480 V was used for testing how drives will respond to voltage sag types; A, B, C and D. The drive response is influenced by sag magnitude, sag duration and phase angle shift. Behavior of the diodes rectifier for conducting is influenced by sag magnitude and phase angle shift represented by sag of types C and D. The diodes rectifiers are reverse biased when it was supplied by voltage sags. Even though there are no charging currents to dc bus capacitor during voltage sags, the drives did not directly trip to certain sag magnitude and sag duration. Sensitivity of the ASD to voltage sag types is presented in voltage tolerance curve. Sag of type A produces highest sensitivity on the ASD and it trips for sag magnitude of 62.5% and 250 milliseconds in duration. Introduction Adjustable speed drives (ASDs) are used widely in many industrials and other applications. Because efficiency improvement, high dynamic performance, energy saving and simple process control are some advantages given by ASD. However, ASDs have been known as sensitive equipment to voltage sags. Industrial process use ASDs to control speed and/or torque of electric motors. An example of an industrial process that uses electronic ASDs is plastic extrusion. The industry produces among other things, plastic bags and carpet fibres. In extrusion process, it usually is done automatically using ASD to control many electric motors in the process. Voltage sag can result in electronics ASD damage and then the process may stop or the motor experience speed variation. This could reduce the quality of product. Sag magnitude and sag duration are main characteristics of voltage sags that very influence on the performance of equipment. Others characteristic such; sag types, phase angle shift, point on wave, recovery voltage etc, are also known can influence of the performance equipment [1]. Sag types can be classified in voltage sag types: A, B, C and D. Type A is due to three phase faults, whereas types B, C and D are due to single phase and phase to phase faults. Sag of types C and D represent sag magnitude and phase angle shift. Effects of AC ASDs to voltage sags found in many of published papers. Available reports in simulation models are documented [2, 3] and experimental tests results [4, 5]. Reference [2], has studied effects of voltage sags on voltage source inverter-fed ASD. Influence of ac inductance on DC voltage drop and ac current peak for three different capacitors were analyzed. Impact of input voltage unbalance and sags on ASD is presented in [3]. The paper investigates impact the voltage sags and unbalance on stresses in the dc bus choke inductor and dc bus capacitor in an ASD and furthermore the influence on the dc link capacitor lifetime. Testing ASDs to voltage sags are addressed in [4]. This study only concentrated on the assessment of voltage tolerance curve of ASDs. Testing was conducted on sensitivity to three phase, two phase and single phase of the voltage sags. The study without take account phase angle shift and do not present the diodes rectifier current behaviour of ASD. Reference [5] presents experimental results on sensitivity of ASD under setting given by manufacturer and resetting low voltage ride through to improve ride through of ASD. Applied Mechanics and Materials Vol. 367 (2013) pp 171-180 Online: 2013-08-16 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.367.171 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 1.9.65.114-13/07/15,04:16:57)