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"Sharpening Skills..... Serving Nation" International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014) International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA. A Methodology to Develop A Simulink Model of Three Phase Induction Motor Manish Kumar Singh1, Madhur Chauhan2, Amit Kumar Singhal3, Nitin Saxena4 [email protected],[email protected],[email protected] [email protected] Abstract— Three phase induction motor is one of the most widely used motors as industrial, commercial and residential load. This motor has the simplest construction, reliable in operation, low initial cost, easy operation, simple maintenance, high efficiency and simple speed control. The popularity of this motor has resulted into lot of research including the transient behaviour of the motor. In this paper, transient performance of three phase squirrel cage induction motor is analyzed with dq0 axis based modeling in synchronously rotating reference frame. The parameters are being calculated by using the standard datasheet given by the manufacturer of the motors. The parameters of the motor are calculated first by using the MATLAB program then proposed system is developed and simulated by using MATLAB/SIMULINK. This paper gives the step by step procedure for developing the simulation model of induction motor in MATLAB Simulink using library Sim Power System. Index Terms— Three phase induction motor, MATLAB, transient behaviour, equivalent circuit parameters I. INTRODUCTION In modern electrical technologies, application of the induction motors in speed and position controlled drives have been increased drastically. The main reason behind this is that the large-scale development of the AC induction motors over traditionally used DC motors. To obtained high static and dynamic qualities of these AC drives, control engineers need more information about the control objective. Therefore, the importance of the characteristics and parameter calculation of the induction motor has gone up. Generally, an induction motor dynamics is simulated in circuit simulators like PSpice, its steady state model is used, but for electrical drive studies, the transient behavior is also useful. One of the major advantage of Simulink over circuit simulators is the in modeling the transients of electrical motors. As the equations are known, any control algorithm can be developed in Simulink. A connection to the network and starting of the induction motor is transient effect. Starting the induction motor is followed by a current and torque surges. rediffmai.com3, Any programming language or simulation program can be used for induction motor simulated model. In this paper, MATLAB Simulink model is used after calculating the equivalent circuit parameters of the induction motor. The calculation is done by developing an m file. Basic concepts are used to complete the all necessary calculations. In most of the paper parameters are being calculated by performing the actual no load and blocked rotor test. For the student working on the simulink model, it is quite tough to do actual test for every motor for calculating the circuit parameters used in defining the simulink model box of induction motor. So, step by step method is being discussed in this paper for calculating the desired parameters without involving into the actual test on the motor. Though, this method gives the approximate results but it may be good for the starting the working on the simulink model. In this paper, MATLAB/Simulink is used to simulate the dynamic performance of an induction motor model. This simulated program makes it easy for the user to follow and understand the development process since it also gives full details about the Simulink structure of each of the model equations. Figure 1: Equivalent circuit of per phase induction motor II. EVALUATION OF INPUT PARAMETERS Normally a data sheet is given by the manufacture with every motor. The details provided through this data sheet with the motor are given in Appendix I. An equivalent circuit for the induction motor referred to stator side is given in Figure 1. Lord Krishna College of Engineering (An ISO 9001:2008 Certified Institute) Ghaziabad, Uttar Pradesh, INDIA. Page 93 "Sharpening Skills..... Serving Nation" International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014) International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA. The equivalent circuit model of the induction motor can be drawn for per phase values. By using these data, the parameters of the induction motor shown in Figure 1can be calculated. The procedure for calculating the equivalent circuit parameters are given from Equation 1 to 11. for calculating the parameters, let the induction motor is run on no-load at rated voltage and frequency and input power at no load provides losses (stator copper losses, iron loss, windage and friction loss and rotational loss) for the induction motor. Normally, the rating of the induction motor is the power output of the induction motor. So its input power is calculated for the given efficiency of the motor as; (1) This input power is on stator side as shown in figure 1. So input current is equal to the stator current which is given by; (2) and are the phase voltage and motor power factor respectively. The per phase equivalent impedance, resistance and reactance of the circuit can be approximately determined as: ; (3) ; ; (4) (10) The stator resistance can be found out using the concept of equivalent impendence of the circuit given in Figure 1. For calculating the voltage of rotor side terminal is assumed to be zero i.e. these terminals are assumed to be short circuited. This is done with the help of MATLAB programming. (11) The value of two mechanical parameters friction coefficient B and inertia constant H is given in Appendix II along with the other parameters calculated using Equation 1 to 11 in this section. III. SIMULINK DESIGN OF INDUCTION MOTOR The complete simulink model is developed on m file. The complete model may be broadly classified into four blocks namely input block, supply block, induction motor block and output parameter block. The input block allows selecting either the torque applied to the shaft or the rotor speed as the Simulink signal applied to the block's input. Mechanical input torque is considered here. The mechanical torque is applied in 1 second from no load to full load value. The value of full load torque is calculated by the formula given in equation 11. (12) (5) A term of flux leakage coefficient is defined as; is defined as the rotor speed given by the Equation 12. (13) (6) The core resistance is assumed to be zero in the equivalent circuit. For the supply frequency , the mutual inductance of the motor is calculated as; A signal is given through the ramp signal as shown if Figure 2. The corresponding signal waveform is represented by Figure 3. (7) The rotor resistance can be found for slip s by the concept of ohmic loss at mechanical output; (8) The stator leakage inductances of the equivalent circuit can be formulated as; (9) The rotor leakage inductance of the equivalent circuit is assumed equal to stator leakage inductances in many papers. So same is considered in this paper too. Figure 2: Simulink block for input signal Lord Krishna College of Engineering (An ISO 9001:2008 Certified Institute) Ghaziabad, Uttar Pradesh, INDIA. Page 94 "Sharpening Skills..... Serving Nation" International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014) International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA. Table 2 Parameters of induction motor in simulink model 200 Nominal power, voltage (line-line), and frequency [ Pn(VA), Vn(Vrms), fn(Hz) ]: [ 1.67e+005 400 50] Stator resistance and inductance [ Rs(ohm) Lls(H) ]: [0.02922 0.00056889] Rotor resistance and inductance [ Rr'(ohm) Llr'(H) ]: [0.059175 0.00056889] Mutual inductance Lm (H): 0.0360 Inertia, friction factor, pole pairs [ J(kg.m^2) F(N.m.s) p()]: [.5 .5 2] 180 160 Mechanical torque input to induction motor 140 120 100 80 60 40 20 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 simulation time in sec Figure 3: Mechanical torque input form no load to full load in 1 sec The supply block consists a grounded star connected three phase source of 400 V line to line voltages at 50 Hz frequency. The reference phase angle is set to be zero. The main block in this model is the third block consisting the induction motor block. The block is available in simulink power system library. The main issue for using this is how to decide the configuration and the parameters. On the basis of the Appendix I and II, the configuration and parameters may be decided. The values given to the model is depicted in Table 4 and 5. The initial conditions are satisfied before running the simulink model using powergui available in simulink library. The last block is the output parameter block. The Simulink output of the block is a vector containing 21 signals. These signals may be de-multiplexed by using the Bus Selector block provided in the Simulink library. The output parameters of interest in this model are rotor speed, slip, electromagnetic torque and load torque with respect to time. IV. RESULT AND DISCUSSION As the data sheet given in appendix I, the induction motor is chosen. The parameters are calculated by developing a m file in MATLAB 2010 using the mathematical Equation 1 to11. The results are given in Appendix I. by using these parameters a simulink model is developed for the study of transients of induction motor. The detail discussion about the various blocks of simulink model is done in separate section of this paper. A linear model of mechanical torque input is used for this paper. To provide the smooth staring of induction motor the full load is not applied in the staring of the motor. Time duration of 2 second is used and load is increased gradually from no load to full load which is designed with the help of continuously increasing ramp function as shown in Figure 3. Table1 Configuration of induction motor in simulink model S. No. 1 2 3 4 5 Description Preset model Mechanical Input Rotor Type Reference Frame Mask units Status NO Torque Tm Squirrel Cage Synchronous SI Figure 4: Mechanical load torque disturbance with time Lord Krishna College of Engineering (An ISO 9001:2008 Certified Institute) Ghaziabad, Uttar Pradesh, INDIA. Page 95 "Sharpening Skills..... Serving Nation" International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014) International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA. 800 Electromechanical torque 600 400 200 0 -200 -400 -600 Figure 5: Rotor speed in induction motor with time 0 0.5 1 1.5 2 2.5 time 3 3.5 4 4.5 5 Figure 7: Electromechanical torque in induction motor with time The results of simulink model are shown in Figures 4 to 7. The simulation time used is 5 sec. the mechanical load is increasing from 0 to full load linearly upto 1 sec and then it reaches to its steady state after transients as shown in Figure 4. The rotor speed and slip variation is represented in Figure 5 and 6 respectively. Both the graphs show the transients at the staring and then achieve its steady state value. Figure 6 shows a very interesting behaviour due the gradual variation of load torque upto 1 sec so transients once reduces further comes at time of 1 sec. V. CONCLUSIONS In this paper, implementation of simulink model for induction machine has been introduced. Unlike most other induction machine model, parameters are fisrt calculated using MATLAB programming. Figure 6: Slip variation in induction motor with time Lord Krishna College of Engineering (An ISO 9001:2008 Certified Institute) Ghaziabad, Uttar Pradesh, INDIA. Page 96 "Sharpening Skills..... Serving Nation" International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014) International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA. These parameters are calculated with the help of available manufacturer data sheet so the beginners may calculate the data without involving into the real test performance and may use these results for the approximate calculation related with induction motor system model. Individual parameter equations are solved in each block, also configuration and parameters involved for developing the simulink model is given in the paper for the better understanding. Finally, the rotor speed, slip, load torque and electromechanical torque responses of induction motor operation is plotted with time. The author believes that the Simulink will soon become an indispensable tool for the teaching and research of electrical machine drives. REFERENCES [1 ] Miloje M. Kostic,“ Equivalent circuit improvement method for induction motor efficiency,” Electrical Engineering Vol. 25, No 1, April 2012, pp. 31 – 42. [2 ] Stanislav Rusnok, Pavel Sobota, Martin Slivka, Pavel Svoboda, “Assessment transients during starting of induction motor in matlab simulink and verification by measurement,” Advanced Research in Scientific Areas 2012 December, 3/7/2012, international virtual conference, section-11. electronics, electrical systems, electrical engineering,pp. 1672-1676. [3 ] Mukesh Kumar Arya, Dr.Sulochana Wadhwani, “Transient analysis of three phase squirrel cage induction machine using matlab,” International Journal of Engineering Research and Applications Vol. 1, Issue 3, pp.918-922. [4 ] Sifat Shah, A. Rashid, MKL Bhatti, “Direct quadrate (d-q) modeling of 3-phase induction motor using matlab / simulink,” Canadian Journal on Electrical and Electronics Engineering Vol. 3, No. 5, May 2012,pp. 237-243. [5 ] K. S. Sandhu and Vivek Pahwa, “A novel approach to incorporate the main flux saturation effect in a three-phase induction machine during motoring and plugging,” international journal of computer and electrical engineering, vol. 3, no. 3, june 2011,pp. 443-448. [6 ] O. I. Okoro, “MATLAB simulation of induction machine with saturable leakage and magnetizing inductances,” The Pacific Journal of Science and Technology, Volume 5. Number 1. April 2003 (Spring),pp. 5-15. [7 ] D P Kothari,I J Nagrath,Electrical Machines 3rd Edition,Tata McGraw Hill Education Private Limited,New Delhi,2009. [8 ] P.S. Bimbra,Electrical Machinery,7th Edition, Khanna Publishers Private Limited, New Delhi, 2012. [9 ] Prabha Kundur,Power System Stability and Control,5 th Edition, Tata McGraw Hill Education Private Limited, New Delhi,2008. APPENDIX I Rating of motor, Pout=150 kW Line Voltage, VL=400 Volt Power factor = 0.9 lagging =0.9 s= 0.04 Supply frequency = 50 Hz Pole pair=1 APPENDIX II Tm=995 N.m Lm=12.0 mH R1=0.02922 Ω LS=18.936 mH Lr=18.936 mH B=0.5 wb/m2 H=0.5 Amp-turn/m R2=0.2630 Ω Lord Krishna College of Engineering (An ISO 9001:2008 Certified Institute) Ghaziabad, Uttar Pradesh, INDIA. Page 97