V/F Control of Squirrel Cage Induction Motor Drives Without Flux or Torque Measurement Dependency (original) (raw)
Related papers
2010
The history of induction motor started when Hans Christian Oersted discovered the magnetic effects of electric current in 1820. Induction motors are perhaps the most widely used electric motors in industry. They offer reasonable performance, a manageable torque-speed curve, stable operation under load and satisfactory efficiency.The aim of the paper is to investigate the performance characteristic of squirrelcage induction motor.Simulation and experimental results are presented and compared to validate the mathematical model of motor. The purpose of this study has been to devise a mathematical model, which can reliably predict the steady state performance
Improving Mechanical Characteristics of Inverter-induction Motor Drive System
American Journal of Applied Sciences, 2006
An inverter-three-phase squirrel-cage induction motor drive system with improved mechanical characteristics is presented. The proposed system provides mechanical characteristics with constant maximum torque or increased maximum torque and reduced slip speed at frequencies below the nominal frequency. The control algorithm is based on the constant volts per hertz principle using two improvement techniques: keeping maximum torque constant or keeping magnetic flux constant. Performance analysis of the system under different operation conditions was provided. For this purpose, a standard state-space model of three-phase squirrel-cage induction motor, with respect to a synchronously rotating d-q reference frame was derived. The correctness and validity of the derived model of induction motor was verified. The inverter was considered as a static linear element and modeled through its input-output equation based on the modulation index. Three types of controllers were modeled, simulated and experimentally tested. The results show that both suggested control methods improve the system performance. The slip speed has been decreased and the starting torque and maximum torque have been increased. Controller with constant maximum torque can be used in drive systems working with constant load, while controller with constant flux can be used in drive systems working with constant power.
Methods for Varying Speed in Squirrel Cage Induction Motors: A Review
Power Electronics has made possible motor drive schemes which were felt impossible during the last decade. Today, an Induction Motor can be run at any speed by using an inverter. Almost all methods employ the pulse width modulation principle. There is a 3 phase sinusoidal modulation method, a so called "Space vector" method and yet another method which is claimed to be a "Direct Torque Control". These methods have been popularized by power electronics people without much consideration about the motor itself. Presently, these schemes are utilizing the power of Digital Signal Processing controllers to do the switching. Insulated Gate bipolar power transistors are invariably employed. There are frequent failures of these devices due to shorting of the D.C. supply lines. There are other problems as well such as induced switching transients, bearing currents and failure of motor winding. Thus, there are problems yet to be sorted out. This review gives a full account of the methods and discusses the problems underlying their use, along with some suggestions.
The efficiency of induction motor drives operating under variable conditions can be improved by predicting the optimum flux that minimizes the losses. In this study, a Loss-Minimization Controller (LMC) and a Search Controller (SC) are combined. The output from the controllers would drive the field oriented control inverter in order to achieve the optimum flux in the motor that minimizes the losses. For this purpose, a mathematical model for calculating the total power losses as a function of magnetic flux and a factor to obtain feedback as a function of optimum flux were discussed. An LMC-SC vector-controlled induction motor drive system was modelled, simulated and tested. The results have validated the effectiveness of this system in minimizing the motor operating losses, especially at light and medium loads. The proposed controller can be implemented in adjustable speed induction motor drive systems with variable loads, operating below rated speed.
Speed Control of Three Phase Squirrel Cage Induction Motor
International Journal of Engineering Research and, 2015
The paper describes the open loop control of the 3 phase induction motor at variable speed using a 3 phase inverter. The 3 phase inverter is supplied from a 400V DC supply. The 3 phase inverter with 3 legs use IGBTs as switches for the generation of 3 phase output. The switches are controlled by pulses created by the PIC microcontroller. The PWM technique used in this project is sinusoidal pulse width modulation. PIC mi crocontroller is used to generate PWM signals. These low voltage signals are given to opto-couplers. The opto-coupler isolates the controller from high voltage level circuit and raises the voltage level of output. The output is fed to the driver circuit for a half bridge of IGBT. For the protection of IGBTs against the over voltages and from short circuiting we have used bootstrapping arrangement. The PIC microcontroller is used to generate PWM signals at variable frequencies. The frequency can be varied using a manual input to the controller.
Studies on Direct Torque Control-Based Speed Control of Three-Phase Squirrel-Cage Induction Motor
SPRINGERJournal of The Institution of Engineers (India): Series B volume 100, pages259–266 (2019), 2019
Direct torque control (DTC) is the simplest method meant for torque control of a three-phase induction motor. The present study emphasizes speed control by using an external speed loop with DTC controller. The variable torque command is generated from the speed loop using a conventional PI controller which has been implemented in experimental work to validate the simulation results. A fuzzy rule-based speed controller has been developed in this study for comparison purpose. The speed response is faster using conventional PI controller, but fuzzy controller minimizes the ripple content in torque. The design of the speed controller has been made economical by using low-cost discrete electronic hardware components.
Different mathematical models have been used over the years to examine different problems associated with induction motors. These range from the simple equivalent circuit models to more complex d,q models and abc models which allow the inclusion of various forms of impedance and/or voltage unbalance. This paper presents speed torque characteristics of induction motor which are calculated on the basis of a mathematical model. This technique is in compliance with the IEEE standard test procedure for polyphase induction motors and generators. Induction machines are the major electromechanical conversion devices in industry. There is a mathematical model of induction motor which is designed from the parameters taken from Machine lab. Through this model we can calculate major features of induction motor very easily. This model solves the issue of torque calculation in three phase squirrel cage induction motor of Machine lab. These results checked on a simulink Model for induction motor fed by PWM inverter. The dynamic simulation is done which is an important tool in the validation of the design process of the motor drive systems and also removes resulting error in the prototype construction and testing. The results obtained by Simulink designed model were encouraging when compared to the design made by practical experience.
International Journal of Applied Mathematics Electronics and Computers, 2019
3-phase induction motors are widely used in industrial applications such as pumps, blowers, compressors, conveyors, etc. In addition, single-phase motors also have domestic use. For this reason, the design of the induction motor is of great importance. During the design, according to the parameters given as input, there are many situations that are contradictory to each other in order to achieve the goal. For example, if high efficiency is required, the motor size and the price will increase, and if lower price is required, other performance characteristics should be ignored. In the practical design of an induction motor, the designer has to comply with a number of constraints because of the large number of input variables. For this reason manual calculation becomes a very long and difficult process. To overcome this tiresome process, it is necessary to create a computer aided program or simulation model to determine the induction motor design parameters. In induction motor design, many parameters directly affect motor performance. Therefore, the selection of these parameters is of great importance. The output coefficient (C0), which takes place in the first steps of the design process, also has a great influence on the motor design. In this paper, a program for optimizing design of 3-phase induction motors written in MATLAB is presented. The structure of the program is modular and therefore can be modified for the various requirements of the induction motor design. C0 constant, one of the design parameters, also varies with some other parameters. The most important ones are the specific electrical loading coefficient (A1) and the specific magnetic loading coefficient (Bav), making dramatic effect on the output coefficient. The effect of the variation of the C0 constant on the performance of the induction motor was investigated in the study. Stator inner and outer diameter, stack length, stator and rotor slot parameters, equivalent circuit parameters, losses and efficiency was obtained according to the change of Bav and A1 values. The obtained results are given and interpreted in tables and graphs.
New relation to improve the speed and torque characteristics of induction motors
Revista Facultad De Ingenieria, 2015
Squirrel cage induction motors are employed in a wide variety of applications. Operating at constant speed is required in some applications, whereas variation of this parameter is required in others, as in the provision of mechanical energy to electrical vehicles. The performance of an electric vehicle is specified by the characteristics of the electric motor. The adequate relation between the voltage magnitude and the frequency of its power source makes the motor satisfy the electric vehicle requirements. The voltage magnitude is a function of the frequency of operation. If the V-f relation is adequate, the motor speed response could be improved. A new V-f relation that improves the speed response of the single squirrel cage induction motor is presented and is defined by a frequency factor. For motor speeds below the nominal value, the torque capacity of the motor is preserved with the proposed relationship.