DIGITAL SIGNAL PROCESSOR BASED V/f CONTROLLED INDUCTION MOTOR DRIVE

Third International Conference on Emerging Trends in Engineering and Technology DIGITAL SIGNAL PROCESSOR BASED V/f CONTROLLED INDUCTION MOTOR DRIVE Mr.C.S. Kamble Research scholar, Electrical Engg. Department, G.H.Raisoni College of engineering, Digdoh Hills, Hingna Rd Nagpur, ck_6sense@yahoo.in Prof. J. G. Chaudhari Ass.Professor.Electrical Engg. Department, G. H. Raisoni College of engineering, Digdoh Hills, Hingna Rd Nagpur. adshish_chaudhari123@rediffmail. com Dr. M.V. Aware Professor,Electrical Engg. VNIT,Nagpur. mva_win@yahoo.co.in Abstract The TMS320 - based control systems have numerous advantages. The high processing speed of the TMS320 family allows sophisticated control techniques to be used to build a high- precision control system. The experimental results for the V/f control of 3-hp induction motor drives controlled by a digital signal processor micro 2407 TMS320 chip have verified the effectiveness of the proposed scheme. The controller structure design is realized using a dedicated Digital Signal based on voltage/frequency (V/Hz) control scheme Processor, designed specifically for motor that transforms the three phase motor speed into control, the controller structure consists of faster voltage and generating input of sine wave of PWM. Inner sin generation PWM control loops and using these voltage components, the AC induction voltage collection and speed controller loops motor can be handled in the similar way & smooth control is possible. Keywords- Induction motor drives, V/Hz control, PWM modulation, IPM module, DSP 2407 Introduction: Judged in terms of fitness for purpose coupled with simplicity, the induction motor must rank alongside the screw thread as one of mankind s best inversions. The induction motor (IM) has dominated a number of fixedspeed applications because of its reliability and low maintenance operation compared to DC motors. But speed control had been one of the obvious shortcomings which impeded IM applications in some industrial fields, such as hydraulics. On the contrary, controlling the speed of a brushed DC motor is simple. This relationship is linear to the motor's maximum speed. In addition, most industrial DC motors will operate reliably over a speed range of about 20:1 -- down to about 5-7% of base speed. This is much better performance than comparable AC motors. However, in the last two decades, with the evolution of power semiconductor devices and power electronic converters, the IM [7] is also well established in the controlled-speed area. High performance Digital Signal Processor (DSP) s introduction makes complicated control algorithms, such as flux vector control available, which means that Alternating Current (AC) motors can be applied to accurate motor speed control as DC motor. Meanwhile, an AC induction motor, compared with a DC motor, is relatively inexpensive, since the windings consist of metal bars which are cast into steel laminations that make up the remainder of the rotor and the stator windings can easily be inserted in slots in stator laminations. An induction motor, at least the cage variety, has no brushes, no moving parts other than the rotor, and virtually no maintenance. As a result, AC motors are progressively replacing DC machines in variable-speed applications. Three-phase induction motor is widely used in many industries because of its simple Construction and free maintenance. However, to get a good performance, the corresponding Controller needs more complex signal processing than that of other motor. Fortunately, this problem can be overcome using Digital Signal Processor (DSP) having the capability to perform the associate signal computation [1] easily and quickly such that the voltage frequency (V/Hz) control can be realized. Voltage frequency (V/Hz) control structure [6] is used in order to make the induction motor can be operated similarly to that of direct current motor where the three-phase PWM signal is transformed two dimensional frequencies and Voltage to change the speed of motor. I. MOTOR MODEL A simple per phase equivalent circuit model of an induction motor is a very important tool for analysis and performance prediction under steady-state conditions. to analyze the operating and performance characteristics of an induction motor, an equivalent circuit can be drawn. We will consider a 3 phase, y connected machine, the equivalent circuit for the stator is as shown below: 978-0-7695-4246-1/10 $26.00 2010 IEEE DOI 10.1109/ICETET.2010.168 345

Figure 1 Equivalent Circuit for the stator Where, V 1 Stator Terminal Voltage I 1 Stator Current R 1 Stator Effective Resistance 1 Stator Leakage Reactance 1 Stator Impedance (R 1 1 ) I Exciting Current (this is comprised of the core loss component Ig, and a magnetizing current I b ) E 2 Counter EMF (generated by the air gap flux) The counter EMF (E 2 ) is equal to the stator terminal voltage less the voltage drop caused by the stator leakage impedance. E 2 V 1 - I 1 ( 1 ) (1.1) E 2 V 1 - I 1 (R 1 1 ) (1.2) In an analysis of an induction motor, the equivalent circuit can be simplified further by omitting the shunt reaction value. The core losses associated with this value can be subtracted from the motor Power and Torque when the friction, windage and stray losses are deducted. The simplified circuit for the stator then becomes: Figure 2 Simplified Circuit To complete the circuit, the component for the rotor equivalent must be added. Figure 3 Equivalent Circuit I 2 Rotor Current R 2 Rotor Resistance 2 Rotor Reactance 2 Rotor Impedance (R 2 / S 2 ) x x Air Gap Impedance What the stator sees in the air gap is the equivalent of putting impedance (equal to R 2 /S 2 ) across E 2. In the analysis, all components in the motor equivalent circuit are referred to the stator circuit. RF R f f (R 2 / S 2 ) in parallel with x. The characteristics of an induction motor, the speed, current, starting torque, maximum torque, the motor losses and efficiency can all be determined from an analysis of the equivalent circuit. II. IPM MODULE (PEC16DSM) In the IPM Module shown in fig has the three diode bridge rectifier with capacitors is provided which gives the rectified DC voltage to IGBT based IPM. In which the IGBT intelligent Power Module of 25A, 1200V is used which consist of three phase inverter or a four quadrant chopper which requires six switching devices, six antiparallel diodes and a switching device for braking. In addition all six switching devices (IGBT) require gate drive circuitries. All these require many external interconnections with additional inductance, causing additional over voltages across the IGBT. IGBT power module consist of six IGBT, six anti-parallel diodes and the breaking switch, all in single unit, on insulated semiconductor substrate. Circuiteries for detecting over current rise in temperature are also built-in. Such modules are called intelligent Power Module. 346

I1 I2 I3 BREAK I4 HV + V. DSP PROGRAMMING R Y B Vdc v er PWM2 IFM PWM1 Figure 4 IGBT Based Connection diagram III. DSP PWM TESTING UNIT The DSP PWM testing unit is well-equipped testing unit,is shown in fig.5 which is useful in verification of various programs-written in Micro-207 trainer. This unit has various features which enables the user to verify programs based on Micro-207 trainer. The program for fixed PWM, which can be executed in the Micro-207 DSP trainer and its output waveforms with load can be observed using this testing Unit. PWM3 PWM4 PWM5 PWM6 HV - The DSP is programmed to generate the pulse width modulated signal of 5 KHz with 20% of duty cycle, with micro-207 trainer. The generation of PWM can be verified by using an oscilloscope. The DSP is programmed with the help of some recommended software. The software we require for simulation and programming as follows i. C program ii. CC Studio iii. Matlab VI. Motor No. of phases hp rating Current rating Rated speed RESULTS Squirrel Cage Induction Motor 3 phase 1 hp 1.A 115 RPM Power Factor 0. 1. OPEN LOOP V/F CONTROL TABLE 1 OPEN LOOP V/F CONTROL OF INDUCTION MOTOR (NO-LOAD) Voltage (Volt) Frequency (Hz) V/f Ratio Figure 5 PWM Testing Unit T A B 150 0.2 121 3.71 100 27.27 21 3.66 0 23.23 725 3. IV. INPUT/OUTPUT SPECIFICATION TABLE 2 OPEN LOOP V/F CONTROL OF INDUCTION MOTOR (ON-LOAD) a) Input 3-phase 15 10% AC supply b) Output 3-phase variable voltage and variable frequency or dc voltage c) Bridge Rectifier 25A, 1200V d) IGBT Intelligent Power module 25A, 1200V e) Breaking IGBT 10A. Voltage (Volt) Frequency (Hz) V/f Ratio 150 0.2 121 3.71 100 27.27 21 3.66 0 23.23 725 3. 347

3. PWM OUTPUT SIGNALS DURING RUNNING CONDITION OF MOTOR Figure 6 Open loop of motor (No-load) Fig. 9 PWM 1 Figure 7 Open loop of motor (On-load) Fig. 10 PWM 2 2. CLOSED LOOP V/F CONTROL TABLE 3 CLOSED LOOP V/F CONTROL OF INDUCTION MOTOR (NO-LOAD) Voltage (Volt) f (Hz) V/f Ratio Set speed Fig. 11 PWM 3 200 27.22 51 7.3 53 20 3.3 1216 7.30 1217 330. 110 7.2 11 Fig. 12 Stator Input Current I 1 Fig.8 Closed Loop of Motor (No-load) 348

VIII. REFERENCES Fig. 13 Stator Input Current I 2 Fig14 DC Link Voltage, V DC [1] A.M. Trzynadlowski, DSP controllers-an emerging tool for electric motor drives,ieee Ind. Electron. Soc. Newslett,pp.II- 13,Sept.2006 [2] Bin Huo and AndrzeM. Trzynadlowski., Random Pulse Width PWM Modulator for Inverter-fed Induction Motor Based on the TMS320F20 DSP Controller, IEEE transaction on Industrial Electronics,Vol.-1.May-2006. [3] Giuseppe S.Bua, Control of DSP based PWM inverter fed AC motors - A survey, IEEE trans.on Industrial Electronics,vol.51,no., Aug-200. [] Eun-Chul Shin, tae-sik Park, Won-Hyun Oh, Ji- oon ou., A Design Method of PI Controller for an Induction Motor with Parameters Variation, IEEE, 2003,pp. 0-13. [5] Gilbert Sybille, Patrice Brunelle, Hoang Le-Huy, Theory and Applications of power System Block set, a MATLAB/SIMU LINK Based simulation Tools for Power system, IEEE 2000,pp.77-77. [6] Rodolfo Echavarria, Sergio Horta, Marco Oliver., A Three phase motor drive using IGBT s and Constant V/F control with slip regulation, San Luis Fotosi, Mexico, October 16-1. 15, p.p.7-1. [7] P. Pillay, Senior Member, IEEE, and V. Levin, Mathematical Models for Induction Machine, New Orleans, LA,15, pp. 606-616. [] G. R. Slemon, Electrical Machine for variable frequency drives, IEEE Proceedings, vol. 2, no, pp.1123-113 August 1. [] Bose Bimal K., Variable Frequency Drives-Technology and Applications (Invited Paper), Condra chair of Excellence in Power Electronics TN, 376, USA. Pp.1-1. [10] Stephen T. Even, Variable frequency Drive Principle and Practices: AC motors for Variable frequency Application, pp.- 10. VII. CONCLUSION This paper presented V/f controlled voltage-source inverter fed induction motor. TMS32O-based control systems have numerous advantages. The high processing speed of the TMS320 family allows sophisticated control techniques to be used to build a high-precision control system. The fast processing of TMS320 family allows high sampling rotes to be used, thus giving analog like performance and minimizing delay time. With the DSP controller an intelligent control approach is possible to reduce the overall system costs and to improve the reliability of the drive system. Using IPM Module and DSP Programming for various voltage modulation technique for inverter, the Induction motor is controlled for Open loop as well as closed loop operation for no load and load conditions. Generation of fixed PWM has verified with the help of PWM Testing Unit. Braking and Reversal of Induction motor is also studied. 349