ISSN (Print) : 2320 – 3765 ISSN (Online): 2278 – 8875 International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering (An ISO 3297: 2007 Certified Organization) Vol. 3, Special Issue 2, April 2014 Copyright to IJAREEIE www.ijareeie.com 556 Design of Active Filter to Minimize the Effect of Long Cables On Inverter Fed Induction Motor M.Umapriya 1 , K.Kanchana 2 , V.Rajini 3 PG Student [M.E.EMBEDDED SYSTEMS], Dept of EEE, Saveetha Engineering College, Chennai, Tamilnadu, India 1 Assistant Professor, Dept of EEE, Saveetha Engineering College, Chennai, Tamilnadu, India 2 Professor, Dept of EEE, SSN Engineering College, Kalavakkam, Tamilnadu, India 3 ABSTRACT: Inverter fed Induction motor drive systems are widely used in industrial applications because of their energy efficiency and flexible control. The motor is subjected to over voltages due to long cable length, fast rise/fall time of inverter pulses and impedance mismatch between cable and motor. The overvoltage causes premature failure of the motor insulation. The proposed active filter reduces the voltage surge and increase rise/fall time of the voltage at the motor terminals. In this paper an active filter is designed and simulated for 3-phase PWM Inverter Fed 1-hp Induction Motor drive using Simulink for different cable lengths. KEYWORDS: Overvoltage,Filters,PWM,Induction Motor. I. INTRODUCTION Three phase induction motors are most widely used motors in industrial automation. It is often required to control the output voltage of the inverter for the constant voltage/frequency (V/F) control of an induction motor. PWM (Pulse Width Modulation) provides constant V/F control of an induction motor. The output voltage waveform from a PWM IGBT inverter typically has a carrier frequency in the range of 1-20kHz and the rise/fall times of the inverter output are typically in the range of 0.05 to 0.06ߤs. Due to fast switching pulses, the transmission line effect and the reflection which occur at the rate of the switching frequency of the inverter, high peak voltage can be experienced at the motor terminals. The characteristic impedance of induction motor is normally 50 to 100 times greater than the characteristic impedance of cable, so the voltage is reflected back towards the inverter. The absolute peak voltage is equal to the sum of the incident peak voltage travelling toward the motor plus the reflected peak voltage[1]-[4]. Thus the overvoltage at the motor terminals depends on the distance between the motor and inverter as well as on the impedance mismatch between the cable and motor surge impedance and switching frequency of the inverter. This overvoltage cause premature failure of the motor [4].The objective of this paper is to study overvoltage phenomena and to reduce the voltage surges and increase rise/fall time of the voltage at the motor terminals. There are two remedial measures put in place to protect themotor against insulation damage. The first one is to use over sized motors or inverter-duty motors with enhanced insulation system that can withstand high dielectric stress. The second one is to use passive filter networks connecting to the entire drive system [7]–[8].The drawbacks of passive filters such as bulky in size and power loss can be reduced by using the active filter.The proposed active filter is designed and simulated using Simulink. II. HIGH FREQUENCY MODEL OF CABLE AND INDUCTION MOTOR To obtain the high frequency parameter of the cable, two types of tests have to be carried out for the measurement of short circuit and open circuit impedances. The high frequency model of cable is shown in Fig.1 that provides a sufficiently accurate response over the frequency range of the voltage pulse[5]. The proposed model for the ac motor input impedance is based on the high-