FAULT ANALYSIS FOR VOLTAGE SOURCE INVERTER DRIVEN INDUCTION MOTOR DRIVE

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1 International Journal of Electrical Engineering & Technology (IJEET) Volume 8, Issue 1, January- February 2017, pp , Article ID: IJEET_08_01_001 Available online at ISSN Print: and ISSN Online: Journal Impact Factor (2016): (Calculated by GISI) IAEME Publication FAULT ANALYSIS FOR VOLTAGE SOURCE INVERTER DRIVEN INDUCTION MOTOR DRIVE M. Dilip Kumar Research Scholar, JNTUA, Ananthpur, Andhra Pradesh, India. Dr. S. F. Kodad Professor and HoD, PESITM, Sivamogga, Karnataka, India Dr. B. Sarvesh Professor, JNTUA, Ananthpur, Andhra Pradesh, India ABSTRACT Induction motor is the commonly used motor for drive applications in almost many industries now-a-days due to its simple and robust construction. Speed control of induction motor is required depending on the type of application. Speed of the induction motor can be varied by varying terminal voltage or frequency. Variable voltage and frequency can be fed to induction motor using an inverter circuit which is found efficient method of controlling induction motor drive. Inverter consists of power electronic switches and faults are of common occurrence in inverters due to failure in switching cell. This paper presents the fault analysis of inverter driven induction motor with switch open and switch short fault conditions. Performance characteristics of induction motor was studied before and during fault condition along with analysis of phase voltage, line voltage and line current from inverter. Simulation work was carried out for the proposed work using MATLAB/SIMULINK software and results were presented for switch open and switch short type of fault conditions. Key words: open fault, short fault, induction motor drive and inverter. Cite this Article: M. Dilip Kumar, Dr. S. F. Kodad and Dr. B. Sarvesh, Fault Analysis For Voltage Source Inverter Driven Induction Motor Drive. International Journal of Electrical Engineering & Technology, 8(1), 2017, pp INTRODUCTION Motors are electromechanical machines which convert electrical energy to mechanical energy. The first electric motor was developed in 18 th century with the principle of faradays laws of electromagnetic induction. Motors replace human intervene in many mechanical applications and were found providing ease to the human beings. Development of motors paved a path for automation in almost all applications increasing the efficiency of the process. AC and DC motors are commonly known types in electric motors classified based on the supply given to them. DC motors works with the support of commutator and brush assembly decreasing the system performance due to sparks and wear and tear. AC type of motors is found 1 editor@iaeme.com

2 M. Dilip Kumar, Dr. S. F. Kodad and Dr. B. Sarvesh suitable for many applications requiring less maintenance. Induction motor is a type of AC motor works on the principle of electromagnetic induction consisting of windings on rotor and stator parts. Induction motor is very robust in construction which is needed in industrial applications. Induction motor requires very less maintenance and can be very handy when used polluted environment in industries. Speed and torque characteristics are very fine in nature and induction motor found to very much suitable in industrial applications. Industries employ motors for mechanical operations and motors with drive system are used. Induction motor drive is very much used in industries [1-2]. Speed of the induction motor can be varied by varying its terminal voltage or frequency of supply. Varying any one parameter mentioned can vary the speed of induction motor. But varying both terminal voltage of induction motor along with the supply frequency maintaining constant voltage to frequency ration is prominent and efficient method in controlling the speed of induction motor [3-4]. Varying terminal voltage and frequency of supply to induction motor can be possible by driving induction motor with an inverter circuit. Power electronic converter like inverter can produce output with variable frequency and also can produce variable voltage. Controlling inverter can produce required supply frequency with terminal voltage to excite induction motor with variable speed operation [5]. Figure 1 Schematic diagram of inverter fed induction motor Fig.1 shows the schematic arrangement of inverter fed induction motor drive. Supply from grid is rectified to DC type of power using a simple diode bridge rectifier and inverted to AC type to feed induction motor using inverter producing variable voltage and frequency to rotate induction motor drive at required speeds. Inverter consists of power electronic static switches and is subjected to faults very often [6]. Fault conditions may occur due to malfunctioning of switching cells in inverter. Switch open or switch short type of fault is most in occurrence and consists of 38% of total faults in inverters. Fault condition in inverter [7-8] can distort the phase voltage, line voltage and line currents of inverter feeding induction motor. This can lead to distort the performance characteristics of induction motor where torque, speed and stator current waveforms might be disturbed. Motor runs with distorted speed damaging the machine parts in long run with fault condition in inverter. This paper presents the fault analysis of inverter driven induction motor drive. Fault conditions of switch open and switch short were considered to study the performance of induction motor drive under faulty condition. Inverter output characteristics were also analyzed due to faulty condition in inverter. Simulation work was carried out for the proposed work using MATLAB/SIMULINK software and results were presented for switch open and switch short type of fault conditions. 2 editor@iaeme.com

3 Fault Analysis For Voltage Source Inverter Driven Induction Motor Drive 2. INVERTER FED INDUCTION MOTOR DRIVE Figure 2 Circuit representation of inverter fed induction motor For variable speed operation of induction motor, variable voltage and frequency are required. Variable supply frequency with voltage can be obtained using inverter fed to induction motor for variable speed operation. Circuit representation of inverter fed induction motor for variable speed operation is depicted in figure 2. Inverter is a circuit that converts DC type of supply to AC type and needs a DC source for its operation. The grid supply is of AC type and for induction motor drive operation fed from inverter, AC supply from grid needs to be rectified to DC. A simple diode bridge rectifier converts AC supply from grid to DC. The DC output from diode bridge rectifier is made stiff using a DC link capacitor. Rectified DC through DC link capacitor is fed to inverter for inverting DC to AC type of supply. By controlling the switches in inverter, required output frequency with desired output voltage can be obtained from inverter through which induction motor can be run at desired speed. 3. FAULT CONDITION IN INVERTER FED INDUCTION MOTOR Figure 3 Inverter with switch open fault 3 editor@iaeme.com

4 M. Dilip Kumar, Dr. S. F. Kodad and Dr. B. Sarvesh Figure 4 Inverter with switch short fault Inverter consists of static power electronic switches and by proper switching of power switches produces desired output. Static power switching cell is subjected to faults very commonly and can affect the output of inverter with faulty condition. Switch open and switch short type of inverter faults are most common in occurrence. Switch open type of fault opens one of the power switch IGBT in inverter and thus affecting the performance of connected load induction motor drive. Figure 3 shows the switch open fault in one switching cell in one of the phase of inverter. Due to switch open fault in one switching cell, the phase current is discontinued to induction motor and creates unbalance condition in line currents. Due to increase in line voltage of other two phases, two loaded phases might be heavily loaded eventually leading to breakdown of supply to induction motor. With this condition, continuity of supply is not provided to the load. Open type of switch fault distorts the torque making the speed of the motor to distort. Speed distortion can produce unwanted sound and affects the mounting of machine. Switch short type of fault short circuits one of the power switch IGBT in inverter and thus affecting the performance of connected load induction motor drive. Figure 4 shows the switch short fault in one switching cell in one of the phase of inverter. Due to switch short fault in one switching cell, the phase current is increased in faulty phase above nominal value increasing the winding temperature inside the motor. Increase in currents due to switch short faults damages the motor windings due to high currents. High currents lead to eventually open the complete faulty phase of inverter. 4. RESULTS AND DISCUSSIONS 4.1. Case 1: Switch open fault Figure 5 Three phase line voltage of inverter with switch open fault 4 editor@iaeme.com

5 Fault Analysis For Voltage Source Inverter Driven Induction Motor Drive Three phase line voltages of inverter are shown in figure 5. Switch open fault was introduced at instant 0.5 seconds. Before fault the line voltages are normal in shape with average value equals to zero indicating no fault condition and maintained nearer constant peak of 900V. After fault is introduced at 0.5 seconds, the line voltages are distorted with average value not equal to zero. Figure 6 Three phase voltages of inverter with switch open fault Three phase voltages of inverter are shown in figure 6. Switch open fault was introduced at instant 0.5 seconds. Before fault the phase voltages are normal in shape with average value equals to zero indicating no fault condition maintaining constant peak of nearer 450V. After fault is introduced at 0.5 seconds, the phase voltages are distorted with average value not equal to zero. Figure 7 Three phase Line current of inverter with switch open fault Three phase line voltages of inverter are shown in figure 7 with switch open type of fault in inverter. Fault was introduced at 0.5 seconds in inverter and before faulty condition, line currents are normal in shape with constant peak and magnitude of nearer 40A. After the introduction of fault, line currents in three phases are unbalanced and over loading two un-faulty phases and the faulty phase line current is distorted. Figure 8 Performance characteristics of induction motor with switch open fault 5 editor@iaeme.com

6 M. Dilip Kumar, Dr. S. F. Kodad and Dr. B. Sarvesh The performance characteristics of induction motor before and during open fault condition was shown in figure 8. Since fault was introduced at 0.5 seconds, the speed, torque and stator currents of induction motor are normal with 1500rpm, 20Nm and 40A respectively before switch open fault. After the introduction of fault, speed curve is distorted along with torque waveform. Stator current also distorted during fault condition Case 1: Switch short fault Figure 9 Three phase Line voltage of inverter with switch short fault Three phase line voltages of inverter with switch short fault are shown in figure 9. Switch short fault was introduced at instant 0.5 seconds. Before fault the line voltages are normal in shape with average value equals to zero indicating no fault condition. After fault is introduced at 0.5 seconds, the line voltages are distorted with average value not equal to zero. Figure 10 Three phase voltage of inverter with switch short fault Three phase line voltages of inverter with switch short fault are shown in figure 10. Switch short fault was introduced at instant 0.5 seconds. Before fault the line voltages are normal in shape with average value equals to zero indicating no fault condition. After fault is introduced at 0.5 seconds, the line voltages are distorted with average value not equal to zero. Figure 11 Three phase Line currents of inverter with switch short fault 6 editor@iaeme.com

7 Fault Analysis For Voltage Source Inverter Driven Induction Motor Drive Three phase line voltages of inverter are shown in figure 11 with switch short type of fault in inverter. Fault was introduced at 0.5 seconds in inverter and before faulty condition, line currents are normal in shape with constant peak and magnitude of nearer 40A. After the introduction of fault, line currents in three phases are unbalanced and over loading phases and line current is distorted. Figure 12 Performance characteristics of induction motor with switch short fault The performance characteristics of induction motor before and during short fault condition was shown in figure 12. Since fault was introduced at 0.5 seconds, the speed, torque and stator currents of induction motor are normal with 1500rpm, 20Nm and 40A respectively before switch short fault. After the introduction of fault, speed curve is distorted along with torque waveform. Stator current also distorted during fault condition. 5. CONCLUSION Induction motors are very prominently used in drive applications in industries due to its superior nature of robust construction requiring less maintenance. Speed is regulated for drive application of induction motor using inverter to get variable supply frequency and terminal voltage. Inverter fed induction motor is subjected to faults due to the presence of switching cells in inverter circuit. Switch short type and switch open type of faults were discussed for inverter fed induction motor drive. The characteristics of induction motor with two types of fault conditions in inverter were discussed without fault condition and during fault condition. Line voltage, phase voltages and line currents of inverter are also illustrated without fault and during fault condition. Analysis of fault in inverter will help in finding the alternative solution to mitigate fault and prior knowledge of inverter faults helps in quickly identify the faults to ensure performance from induction motor drive. REFERENCES [1] K.Vijaya Bhaskar Reddy, G.V. Siva Krishna Rao, Modeling And Simulation Of Modified Sine PWM VSI Fed Induction Motor Drive International Journal Of Electrical Engineering & Technology (IJEET), Volume:3, Issue:2, 2012, Pages: [2] A.O.Amalkar, Prof. K.B. Khanchandani, Design And Implementation Of Sensor less Speed Control For Induction Motor Drive Using An Optimized Extended Kalman Filter, International Journal Of Electronics And Communication Engineering & Technology (IJECET), Volume 6, Issue 3, March (2015), pp IAEME 7 editor@iaeme.com

8 M. Dilip Kumar, Dr. S. F. Kodad and Dr. B. Sarvesh [3] M.S.Aspalli.1, Asha.R2, P.V. Hunagund, Three Phase Induction Motor Drive Using IGBTs And Constant V/F Method, International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, Vol. 1, Issue 5, November 2012, pp [4] Alfredo,Thomas A. Lipo and Donald W. Novotny, A New Inductio Motor V/f Control Method Capable of High-Performance Regulation at Low Speeds IEEE Trans. Industry Applications, Vol. 34, No. 4 July/ August [5] M.S.Aspalli, Veerendra.D, P.V.Hunagund, A New generation VLSI approach for V/F control of Three- Phase Induction Motor. Proceedings of the International Conference on VLSI, Communication and Instrumentation, April7th -9 th, 2011, Kottayam, India. [6] Mendes A.M.S and Marques Cardoso A.J Continuous operation performance of faulty induction motor drives under inverter fault conditions (2003) [7] Debaprasad Kastha, Member, IEEE, An Improved Starting Strategy for Voltage-Source Inverter Fed Three Phase Induction Motor Drives under Inverter Fault Conditions IEEE transactions on power electronics, vol. 15, no. 4, July [8] KLIMA, Jiri, Analytical Investigation of an Induction Motor Drive Fed from VSI under Inverter Fault Conditions, The International Conference on Electrical Engineering in [9] Mujib J. Pathan and V. A Kulkarni, Fault Analysis of HVDC Transmission Systems. International Journal of Electrical Engineering & Technology (IJEET), 7 (3), 2016, pp editor@iaeme.com