FIVE PHASE INDUCTION MOTOR GUDLAVALLERU ENGINEERING COLLEGE B.NEELA KUMAR V.VEDAVYAS R.No: 12485A0213 R.No: 11481A02B1 Email: neelakumar213@gmail.com Email: electricalelegnat@gmail.com Ph.No : 9640630111 Ph.No : 8008287664 ABSTRACT This paper introduces two kinds of control schemes: Vector control and direct torque control (DTC). These control schemes can be extensively applied to the operation of a five-phase induction motor using a fully digital implementation. Vector control of the five-phase induction motor not only achieves high drive performance, but also generates the desired nearly rectangular current waveforms and flux profile in the air-gap resulting in an improvement in air gap flux density and an increase of 10% in output torque. The DTC method has additional advantages when applied to multiphase, in this case a five-phase, induction motor. The five-phase inverter provides 32 space voltage vectors in comparison to 8 space voltage vectors provided by the three-phase inverter. Therefore, a more elaborate flux and torque control algorithm for the five-phase induction motor can be employed. Direct torque control of the five-phase induction motor reduces the amplitude of the ripples of both the stator flux and the torque, resulting in a more precise flux and torque control. A 32-b floating-point TMS320C32 Digital Signal Processor (DSP) enables these two sophisticated control techniques to be conveniently implemented with high control precision. Experimental results show that an ideal control capability is obtained for both control methods when applied to the five-phase induction motor and further validates theoretical analysis. INTRODUCTION Vector control and direct torque control (DTC) are two popular control techniques widely applied in motor drive applications. By directly controlling the flux and the torque, both techniques yield fast dynamic response and high performance. In this paper, a corresponding vector control Method of the five-phase induction motor is developed based on the reference frame. The basic underlying principle here is to decouple the five stator phase currents into the flux components, and the torque components, and then to provide independent control of both flux and torque. The objective with vector control of the five-phase induction motor is to generate the fundamental current waveform and associated third harmonic of this fundamental and appropriately to combine these waveforms, thereby inducing the desired nearly rectangular flux in the airgap. As a result, an improvement in the power density and output torque of the fivephase induction motors can be achieved. Direct torque control of the five-phase induction motor is also introduced in this paper. Through the optimal selection of the space voltage vectors during each sampling period, direct torque control provides an effective and direct control of the stator flux and the torque, an alternative to employing current control, a more conventional technique. In the case of the five phase induction motor, direct torque control has unique advantages. Direct torque control of the five-phase induction motor has 32 space voltage vectors with varying magnitudes when employing closed loop operation. Compared with eight space voltage vectors associated with conventional three-phase induction motor drives. The increased number of space voltage vectors provides direct torque control, when operating in closed loop, of the five-phase induction motor, greater flexibility in selecting the inverter switching states and thereby accomplishes a more precise control of the stator flux and torque. From a maintenance and reliability perspective, the benefit achieved with additional space voltage vectors is that the zero sequence vectors need not be chosen. The implication of this is that zero sequence mode vectors have been shown to cause bearing currents which result in pitting and fluting of the motor bearing, thereby reducing the life of the motor. In order to implement these two sophisticated control methods, a 32-b floating-point TMS320C32 DSP is adopted as the central processor. Operating from a 50 MHz clock speed, a performance of 25 MIPS and a peak floating-point performance of 50 MFLOPS allows vector control and direct torque control of the five-phase induction motor with higher processing speed and precision. Experimental results show that ideal control performance is achieved in both control methods for the five-phase induction motor, both of which validate theoretical predictions and analysis. VECTOR CONTROL OF FIVEPHASE INDUCTION MOTOR In this paper, a five-phase induction motor with a full pitch concentrated winding is used. Instead of the traditional sinusoidal winding distribution, the winding structure of the five phase induction motor is designed with a rectangular distribution to better accommodate the quasi-rectangular input currents provided by the five-phase, In order to simplify the vector control method of the five phase induction motor, a combined fundamental current waveform with the third harmonic of the fundamental current waveform, which nearly replicates a rectangular waveform, is considered as the input current of the five-phase induction motor instead of the required rectangular currents. In conjunction with the designed five-phase induction motor geometry, this current profile induces the nearly rectangular flux linkage in the air-gap and thus results in higher power density and more torque output. The principle goal of vector control of the five-phase induction motor is to decouple the stator currents into the flux components, and the torque components, and then to perform independent control on the fluxes and the torques in a manner analogous to separately excited DC motor drives. vector control of the five-phase induction motor enables the fundamental flux and the torque and the third harmonic flux and the torque to be decoupled respectively, achieving independent control of the fluxes and the torques of the five-phase induction motor. The overall system includes two closedloops, an inner current loop and an outer speed loop. Whenever a reference speed is given, the system automatically compares it with the actual speed. According to the motor equation of motion, the speed error directly indicates the torque profile. Therefore, the output of the speed PI regulator is considered as the torque reference value. Correspondingly, the torque component of the stator current can be obtained. FIG: Vector control of a five-phase induction motor. DIRECT TORQUE CONTROL OF A FIVE-PHASE INDUCTION MOTOR Direct torque control (DTC) of induction motors is also a powerful control method for use with motor drives. In principle, the DTC method is based on instantaneous space voltage vector theory. Through the optimal selection of space voltage vectors during each sampling period, direct torque control provides the effective and direct control of the stator flux and torque instead of current control, a more conventional technique. Thus, the DTC strategy is dependent upon the motor-inverter system, the number of space voltage vectors and the switching frequency all of which directly influence the performance of the DTC system. In comparison with three-phase induction motor drives, the five-phase motor drives are supplied with a five-phase voltage source inverter (VSI). In this case, there are two zero voltage states associated with either all of the five upper switches “on” or all of five bottom switches “on”. Additionally, there are thirty nonzero switching modes. The total number of the five-phase inverter switching combinations is (2^5=32) and thus there are 32 corresponding space voltage vectors. In particular, the 32 space voltage vectors are composed of three sets of vectors having different amplitudes and divides the witching plane into ten sectors FIG: Direct torque control of the five-phase induction motor. EXPERIMENTAL SETUP AND HARDWARE STRUCTURES OF THE CONTROL SYSTEM FIG: Space voltage vectors of a five-phase inverter-driven system. Based on the proposed vector control and DTC schemes, a fully digital control system has been implemented. The five phase current regulated inverter, on the right side of the five phase motor, is a natural extension of the standard three-phase inverter. The insulated gate bipolar transistors (IGBTs) are used as switching devices of the inverter. The switching frequency used in the experiment is 10 kHz. The controller indicated at the bottom uses a TMS320C32 DSP to provide vector control, DTC and to drive the five-phase inverter to generate the desired rectangular currents and flux. In this experiment, four channels of analog-to-digital converter (ADC) are used for sampling four phase stator currents through four Hall Effect current sensors of model number HNC-050P. The speed pulse signal generated by a Dynapar H25 speed encoder inputs to the TMS320C32 DSP via one digital input port. After executing the five-phase induction motor control methods, five channels of digital to analog converter (DAC) output the desired current control signals to produce the five channels containing the PWM pulses and are then sent to the SKHI22 IGBT drive circuits. Furthermore, the gating signals are generated to control the five-phase inverter and motor. The DSP-based control system of the five-phase induction motor consists of three interconnected modules: the C32 DSP board, 16I/O8 DSPLINK interface and Pulse Width Modulated (PWM) output circuits. TMS320C32 DSP is used as the central processor of the control system and implements the corresponding control algorithms—vector control and DTC. DC link voltage, the stator currents and the speed are sampled and transmitted to the DSP through the 16I/O8 DSPLINK Interface board. Based on this information, the control system generates the required five-phase PWM gating signals to drive the five-phase induction motor. The TMS320C32 DSP used is a 50 MHz, 32-bit floating-point processor with two on-chip 32 bit timers, an enhanced external memory interface, a two-channel DMA controller and a serial port. This arrangement offers a versatile and powerful development tool for motor drives. FIG: Experimental setup of the five-phase induction motor drive. FIG: Overall hardware architecture of the control system. Below FIG is the functional block diagram of the PWM output circuit. This generates ten channel PWM signals by comparing the outputs of the current PI regulators with a triangular carrier waveform. These signals are then sent to the IGBT drive circuits (SKHI22) to form the five-phase inverter gating signals, which directly drive the fivephase induction motor. SKHI22 assures a dead time of 2 s between the gate signals of the upper and the lower devices as a means to protect IGBTs in each leg from voltage shoot through. Fault protection circuits perform real-time monitoring of the dc link over-voltage (OV), the stator over-voltage, the stator low-voltage (LV) and the stator over-currents (OI), as well as overheating (OH) of the stator windings, so that the PWM outputs can be blocked immediately upon the occurrence of one or more of these faults. FIG: Block diagram of PWM output circuit. CONCLUSIONS Vector control of the five-phase induction motor drive with the combined fundamental and third harmonic current not only achieves high transient and steady state performance, but also provides the desired nearly rectangular current and flux waveforms. This in turn results in improvement of the flux density and about a 10% increase of output torque by injecting the third harmonic of current. Direct torque control is a very practical control method to be applied to the fivephase induction motor. 32 space voltage vectors result in a significant reduction of the torque and the stator current ripples and implement a more accurate control of the flux and the torque. REFERENCES 1. Huangsheng Xu, Member, IEEE, Hamid A. Toliyat, Senior Member, IEEE, and Lynn J. Petersen, Member, IEEEB. K. Bose, “High performance control and estimation in AC drives,” in Proc. 23rd Int. Conf. Ind. lectron. Contr. Instrum., vol. 2, 1997, pp. 377–385. 2. I. Takahashi and Y. Ohmori, “Highperformance direct torque control of an induction motor,” IEEE Trans Ind. Applicat., vol. 25, pp. 257–264, Mar./Apr. 1989. 3. P. Vas, Sensorless Vector Control and Direct Torque Control. New York: Oxford University Press, 1998.