Inverter controlled characteristics of variable frequency induction motors (original) (raw)
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A Low cost modelling of the variable frequency drive optimum in industrial applications
Journal of Energy Systems, 2018
A single or three phase asynchronous motors, or known a squirrel cage motors (SCMs) are represent one of generally using in many industrial applications. They are consuming further than half-percent of the total generated electrical energy. This motor is working at its full speed when it is attached to the main AC- supply. Therefore, speed control of asynchronous motor is necessary to industrial applications that require changeable flow control of fluid (air, water and chemical liquid streaming). There are many methods to control the speed of motors, such as changing the stator number of poles, controlling supply voltage, addition series reactor or resistances. The modern method is Volt per Hertz, or scalar control this method applied by changing voltage and frequency of three-phase supply, or by making a V/f equal to a constant value in this method a large amount of energy can be saved. In this study, analysis and practical implemented to variable voltage Variable Frequency Drive o...
V/F Control of Squirrel Cage Induction Motor Drives Without Flux or Torque Measurement Dependency
International Journal of …, 2011
Based on the popular constant volts per hertz principle, two improvement techniques are presented: keeping maximum torque constant or keeping magnetic flux constant. An openloop inverter-three-phase squirrel-cage induction motor drive system that provides constant maximum torque or increased maximum torque and reduced slip speed at frequencies below the nominal frequency has been modeled, simulated and tested. Load performance analysis of the proposed system under different operation conditions was provided. These principles of operation are extended to the case of operation from variable frequency or variable voltage control method. Finally, the effects of the non-sinusoidal voltage and/or current wave shapes are covered. The results show that both suggested improvement techniques (constant torque or constant flux) improve the steady-state performance A.C. drive system with squirrel cage induction motors. The slip speed has been decreased and the starting torque and maximum torque have been increased, which means that the suggested control techniques can be used in drive systems with short time operating mode under light loads.
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
Analysis of the Asynchronous Motor Controlled by Frequency Inverter Applied to Fatigue Test System
International Journal of Advanced Computer Science and Applications
This research focuses on analyzing the functional and operational parameters of the three-phase induction motor, squirrel cage type; Where the experimental model consists of a fatigue test system operated by two types of control: Control by Frequency Inverter and Classic star-delta control, where the engine load consists of a standard specimen, corresponding to 61.9% of the nominal load of the object of study. Experimental evaluations of this rotary machine are at regular operating conditions. Managing to Record electrical, mechanical, thermal variables; in a database where they were classified, developed, analyzed and interpreted; Highlighting from the graphs, the quasi-constant behavior of the Cos(φ) at 0.754 at different regulated frequency values which lead to a low energy consumption of current 1.88 Ampere with variator with respect to the weighted of 2.04 Ampere without inverter; even with improvements in torque when you are opting to use the drive from a 0.71 N-m to a 0.94 N-m. Likewise, the operation of this machine at low frequencies manifests some damages to normal operation, such as the rate of increase in the operating temperature of 78.76 °C in a short time and with projection to increase. Similarly, the injection of harmonic distortion into the network as a result of using electronic equipment, contributes to the detriment of energy quality.
Development of a mathematical model of frequency controlled induction electric drive
Journal of Vibroengineering
A mathematical model of a frequency-controlled induction (asynchronous) electric drive is proposed, which makes it possible to study electromagnetic and electromechanical processes in an electric drive with any drive mechanism and takes into account the non-sinusoidality of the output voltage of the frequency converter. The block diagram of the algorithms of calculations performed in the "Mathcad" computer application, the results of modeling and their analysis are presented.
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.
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.
Modified Steady-State Analysis of the Current-Source Inverter and Squirrel Cage Motor Drive
IEEE Transactions on Industry Applications, 1981
The "modified" steady-state analysis of the currentsource inverter (CSI) drive given in this paper includes the effects of the following factors neglected in the "conventional" analysis given in present literature: 1) the variation of the ac back electromotive force (EMF) of the induction motor (load) during commutation, and 2) the phase shift of the fundamental component of the line current due to the finite commutation interval. It is shown that the effective leakage inductance of the motor during commutation is lower than the value obtained by the low-frequency blocked rotor test. A procedure for measuring the effective leakage inductance is given. At high stator frequencies the inverter operation is influenced by the conduction of series diodes outside their usual 1200 period. A method of calculating the "critical" frequency where this effect begins to occur is given.