Optimal control of induction motor using high performance. Pdf speed control of induction motors kamakhya basumatary. Click download or read online button to get variable frequency ac motor drive systems book now. If the speed control of the induction motor is done by frequency, the ratio of voltage to frequency must be constant. The preferred method of speed control for squirrelcage induction motors is to vary the frequency of the supply voltage, and the system used for this purpose is known as variable frequency drives or vfd. There are several methods for the speed control of induction motor. Any variable frequency drive or vfd incorporates following three stages for controlling a three phase induction motor rectifier stage. Vfd speed control of three phase induction motor by vf method using pic microcontroller. Singlephase induction motors are widely used in home appliances and industrial control. An induction motor is practically a constant speed motor, that means, for the entire loading range, change in speed of the motor is quite small. Speed control of induction motor by using variable. The speed control of induction motor is done at the cost of decrease in efficiency and low electrical power factor. Torquespeed curve for variable voltage 3 for positive values of slip, the. Introduction speed control of induction motor is necessary in industrial applications.
Firstly threephase induction motor drive system is simulated in various modes using matlabxilinx, then. Voltage source inverter control of induction motor can be operated as a stepped wave inverter or a pulsewidth modulated pwm inverter. Variable frequency drive for induction motor elprocus. Introduction the induction motor im fed by a threephase matrix converter shown in fig. Combining the principles of variable structure, direct. The speed of a three phase induction motor can be varied by varying the supply voltage. Variable frequency control is a method which is used to control the speed of an induction motor. Variable frequency drive or vfd is the way that enables controlling of the speed of induction motor by applying varying frequency of ac supply voltage. The nominal speed is therefore slightly lower than the synchronous speed of 1800 rpm, or w s 188. Variable frequency drives vfds popular speed control devices used in industrial, commercial and residential applications. A variablefrequency drive vfd is a device that controls the voltage and frequency that is being supplied to a motor and therefore controls the speed of the motor and the system it is efficiency is improved. Vector control, also called fieldoriented control foc, is a variablefrequency drive vfd control method in which the stator currents of a threephase ac electric motor are identified as two orthogonal components that can be visualized with a vector. Ac motor speed control variablespeed motor controls and.
When applications required large amounts of power and torque, the induction motor became more efficient to use. Speed control of induction motor using cycloconverter. Design strategy for a 3phase variable frequency drive vfd. This is a brief discussion about variable frequency drive of an induction motor.
This site is like a library, use search box in the widget to get ebook that you want. For controlling the speed of three phase induction motor by vf method we have to supply variable voltage and frequency which is easily obtained. Variable speed drive by using frequency control method is commonly used to control and change the speed of single phase induction motor. While there are different methods for control, variable voltage variable frequency vvvf or vf is the most common method of speed control in open loop. Why use variable frequency drive for induction motor. A variable voltage, variable frequency drive is capable of operating over a wide speed range. Induction motor control is complex due to its nonlinear characteristics. Speed control of three phase induction motor by variable. Speed control of three phase induction motor electrical.
Single phase ac induction motors are one of the widely used motors in the world, yet relatively little woke has been done in the applications of power electronic. Adjustable speed control of induction motor using variable. Variable frequency characteristicsvariable frequency control of induction motor by voltage source and current source inverter and cyclo converters pwm control comparison of vsi and csi operations speed torque characteristics numerical problems on induction motor drives closed loop operation of induction motor drives block. Pdf speed and frequency control of ac induction motor. There are three distinct operating modes, illustrated in the diagrams below. A fullwave power diode based solidstate rectifier converts threephase 50 hz power from a standard 220, 440 or higher utility supply to either fixed or adjustable dc voltage. A variable frequency drive is a system equipped for controlling the rotational speed of an alternating current ac.
We already know that if we change the frequency of supply then we can easily change the speed of induction motor by the. Cycloconverters are used in very large variable frequency drives with ratings from few. Sometimes theyre talking about induction motors, other times not, and they dont specify which is which, or even which induction motor type they are talking about. Huge energy savings potential operating centrifugal fans, pumps and compressors vary frequency of electrical supply to an induction motor to vary the motor speed. The synchronous speed of an induction motor is given by the relation shown below. Ac induction motor speed control so what can we do to control the speed of an ac induction motor. However, recently, it has been increasingly used as variable speed motors driven by an inverter. Design and implementation of an adjustable speed drive. Torquespeed characteristics of three phase squirrel cage. Out of the several methods of speed control of an induction such as pole changing, frequency variation, variable rotor resistance, variable stator voltage, constant vf control, slip recovery. Because these motors typically only have an onoff state of operation, a vfd is needed if multiple operation speeds are desired.
However, some mechanical trains driven by vfd motor systems have encountered torsional. Variable frequency drive advantages vfds implement the most common motor in industry, the standard squirrel cage nema type b induction motor. Speed of a dc shunt motor can be varied very easily with good efficiency, but in case of induction motors, speed reduction is accompanied by a corresponding loss of efficiency and poor power factor. This is why using vfd to control an induction motor was a good idea. Speed control of induction motor by variable frequency control. In the variable frequency drive itself are the most basic components present. Variable frequency can be generated by using this inverter. The system may include transformers for high voltage system. The full range of products covers various voltage ratings. Vvvf techniques for speed control of induction motor. The most popular type is the 3phase, squirrelcage ac induction motor. By controlling the output ac frequency, it is possible to drive the motor at different speeds based on the requirements. Pdf variable speed drive of single phase induction motor. Voltage induced in stator is proportional to the product of supply frequency and airgap flux.
The synchronous speed and therefore, the speed of the motor can be controlled by varying the supply frequency. Variable voltage variable frequency speed control of. The drives have compact dimensions and can be installed side by side to save space. When operated as a stepped wave inverter, transistors are switched in the sequence of their numbers with a time difference of t6 and each transistor is kept on for the duration t2, where t is the time period. The multispeed operation and multipurpose operation are provided by controlling the speed of these motors. His document describes the design road taken when looking at a 3phase variable frequency drive vfd. It gives the possibility to use it to show people about the control of an induction motor and the step towards electric cars is easily made. If the supply frequency increases or flux decreases in the three phase induction motor, it affects the torque. Variable speed and flow capability with standard induction motor. Motor controllers ac variable frequency drives type.
Variable frequency synchronous motor drives springerlink. Variable frequency ac motor drive systems download ebook. The name itself suggests that vfd uses voltage and frequency to control the speed of induction motor. Optimal control of induction motor using high performance frequency converter jerkovic vedrana, spoljaric zeljko and valter zdravko faculty of electrical engineering department of electromechanical engineering, osijek, croatia, email. Power semiconductor drives pdf notes psd pdf notes. They can be used in control of motors used in conveyors and other machinery. Variable frequency control of induction motor drive. Variable frequency drives induction motor control duration. Keywords cycloconverter, split phase induction motor i.
The variable voltage variable frequency supply for an induction motor drive consists of a. Pdf experimental results of variable frequency drive for three. Optimal uf control for induction motors sciencedirect. Load motor, plc programmable logic control, vfd variable frequency drive, speed reference control. In many industries, the induction motors are controlled by variable frequency drives with the. As long as an efficient, variable frequency power supply was not available this meant constant speed operation at fixed frequency. These motor drives are designed to be used in conjunction with a 3phase induction motor. Before discussing the methods to control the speed of three phase induction motor one should know the basic formulas of speed and torque of three phase. The supply voltage should not increase beyond certain limit in order to consider insulation of the stator winding. The 3phase set of currents, each of equal magnitude and with a phase. It is hard to learn anything valueable from that page. The basic idea of an electric motor is to generate two magnetic fields.
Ac voltage to control the speed of the induction motor. Voltage source inverter control of induction motor four. Variable frequency control of induction motor drive synchronous speed, therefore, the motor speed can be controlled by varying supply frequency. The control system of the drive calculates the corresponding. A vfd variable frequency drive is a controller used to control and monitor parameters of induction motor such as speed. Speed control of induction motor by variable frequency control variable frequency control is a method which is used to control the speed of an induction motor. Variable frequency control vf of induction motor 1. The rotor will constantly be turning to align its magnetic field with that of the stator field. Change ac frequency variable speed ac motor adjustable speed drives are known as. If you want to control induction motor speed, save yourself a lot of grief and get a 3phase motor. With the invention of variable voltage, variable frequency drives, use of an induction motor has increased.
Vfd speed control of three phase induction motor by vf. The rvlf advance comes with sensorless vector control as. Advanced motor control pwms readytouse ac induction motor controller ic for lowcost variable speed applications, rev. Variable frequency drive vfd can be used to control the speed of threephase induction motor. Variable speed drive of single phase induction motor using.
Stator voltage control is a method used to control the speed of an induction motor. Induction motors have been traditionally used as constant speed motors supplied by the ac power source. As we already know that the torque developed is proportional to the square of the supply voltage and the slip at the maximum torque is independent of the supply voltage. Speed control of three phase induction motor using. The use of a standard motor means the vfd is suitable not only for new applications, but for retrofitting older existing motors as well.
Induction motors and variable frequency drives vfds are widely used in industry to drive machinery trains. Variable voltage variable frequency control of threephase induction motor in closed loop is the significant feature of the thesis work. Variable voltage variable frequency vf control theory an induction motor compared to a dc motor has some major advantages such as absence of brushes, commutator segments, rugged construction, being cheap, lesser maintenance requirements and smaller. For variable voltage variable frequency vvvf drives, there is a need to control the fundamental voltage of the inverter if its frequency and therefore the frequency of the induction motor. This is the constant torque region where vf control can be applied, with low frequency voltage boosting. Variablefrequency ac motor drives do not require motor speed feedback the way variablespeed dc motor drives do. An843, speed control of 3phase induction motor using.
Speed control of three phase induction motor electrical4u. Stator voltage control of an induction motor circuit globe. Keywords induction motor, speed control, fuzzy logic controller. The synchronous speed and therefore, the speed of the motor. One component defines the magnetic flux of the motor, the other the torque. Request pdf adjustable speed control of induction motor using variable frequency drives our varying industrial needs demand more precise control of the. Setting the nominal power to 3746 va and the nominal linetoline voltage vn to 220 vrms implements a 3 hp, 60 hz machine with two pairs of poles. The speed of a synchronous motor with constant rotor excitation is determined by the stator frequency and the number of poles. A three phase induction motor is basically a constant speed motor so its somewhat difficult to control its speed. Speed control of induction motor using vf technique phase i a thesis submitted in. Speed and frequency control of ac induction motor using variable frequency drive. Variable voltage variable frequency control provides a simple and cost efficient method for openloop speed control of three phase induction motor.
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