The speed control of three phase induction motor from stator side are further classified as. Stator voltage control of induction motor is a method for the speed control of induction motor by changing the stator terminal voltage. This makes the induction motor robust, inexpensive and need less maintenance. This means that there is no need for slip rings and brushes. The speed control of induction motor is done at the cost of decrease in. The rotor will constantly be turning to align its magnetic field with that of the stator field.
Another method of controlling the speed of induction motor drives is the stator voltage control. The threephase induction motor is the easiest motor of this type to understand so these notes start with that type. We know that t he speed of the induction motor is given by, from the above equation, the speed of the motor can be controlled by changing supply frequency and by changing number of poles in the stator. Torque speed characteristics of induction motor slip. Vector control or field oriented control offers more precise control of high performance drives where oscillations in air gap flux linkages are intolerable. This high current is a result of stator and rotor flux, the losses in the. The speed of an induction motor is given as n 120fp 1s.
The stator consists of a series of wire windings of very low resistance permanently attached to the motor frame. The main methods employed for speed control of induction motors are as follows. The characteristics are drawn with rated voltage and frequency supplied to the stator. The converter transforms a reference speed to a reference electrical frequency. Direct torque control dtc is a technique used in variable frequency drives.
Synchronous speed of the rotating magnetic field of an induction motor is given by, where, f frequency of the supply and p number of stator poles. We can change the speed at the stator by, by changing the supply frequency. Speed control of a three phase induction motor fed from a single. Nehrir proposed a technique for speed control of threephase. An induction motor or asynchronous motor is an ac electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. The controller generates reference voltages from the reference frequency by maintaining a constant voltagetofrequency ratio through scalar vf control.
The input to the auto transformer is a fixed ac voltage. Speed control of induction motor 7 ways to control. Feeding a three phase induction motor from a single phase ac supply via a single. Stator voltage is directly responsible for the rotating speed of the rotor. The induction motor is made up of the stator, or stationary windings, and the rotor.
Plc for controlling the operation of induction motor such as forward and reverse direction and speed is. Induction motors are constant speed motors, hence if we desire to use these motors for variable speed applications, the speed can be vary by using ac power. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque. Induction motor and different speed control methods page no.
The squirrel cage induction motor rotor is shorted and so there is no rotor excitation, the rotor voltage equals zero. M but is the case of slip ring induction motor it would be much easier to start the motor. How to control the speed of 3 phase induction motor quora. The speed of the induction motor can be controlled by using auto transfomer. If the voltage injected opposes the rotor voltage, the effective rotor current decreases, which instantly affects the torque. The rotor in an induction motor is not externally excited. During startup, the motor typically draws up to seven times the rated current. Simplified steadystateequivalent circuit of induction motor. Indirect vector control of multi cage induction motor. The basic idea of an electric motor is to generate two magnetic fields. Stator terminal voltage in this method is changed either by adding a series resistor, series inductor, auto transformer, ac controller or ac chopper in stator circuit. If we decrease supply voltage torque will also decrease. Induction motor control by stator voltage control method using plc.
It comes from estimating the magnetic flux from the voltage and current of the motor. In this way, the slip power of main motor is fed to the auxiliary induction motor at a frequency of f 2 s 1 f 1. Torque is proportional to voltage squared and the current is proportional to the voltage. The developed model is studied with constant vf control taking the boost voltage into. As its name indicates stator is a stationary part of induction motor. Induction motor drives starting braking speed control of. Then, equation 1 can be shown in terms of magnitude as.
In this post let us see what are the various methods to control the speed of induction motor. So, if the stator voltage is reduced the speed reduces and similarly if the stator. To control the speed of induction motor many techniques and drives are available out of which vfd variable frequency drive is used here. Induction motor speed control by stator voltage control ieee xplore. Speed control of three phase induction motor electrical. Pdf study of stator voltage control method for induction motor. The principle of operation of this motor is based on the. Sensorless field oriented control of 3phase induction motors using control law accelerator cla manishbhardwaj abstract this application report presents a solution to control an ac induction motor using the control law accelerator cla which is a small foot print coprocessor present on some of the microcontrollers from the c2000 family of. Speed control of induction motor detailed explanation. An induction motors rotor can be either wound type or squirrelcage.
We can control the speed at stator side and at rotor side also. Speed control of induction motor by variable frequency control. Actual speed of an induction motor is given as n ns 1 s. Variable voltage and variable frequency inverter induction motor e g vs. When induction motor is connected in star connection stator phase voltage reduced by 12 times the line voltage. Explain starting methods of 3 phase induction motor.
Then we have at steady state, v kj 1 where v stator voltage v. A threephase induction motor provides a smoother motion with more control and accuracy of positioning for the motor, and there are designs of motors with five or more poles. 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. Speed control of three phase induction motor by stator voltage. Main motor stator terminal is connected to the supply main and the slip power of main motor is fed to the stator terminals of auxiliary induction motor through slip ring as shown in figure below. Record all nameplate information for the induction motor. Sensorless field oriented control of 3phase induction. Block diagram of the open loop voltshz control for an induction motor.
A stator winding is placed in the stator of induction motor and the three phase supply is given to it. In case of three phase induction motor torque produced is given by t. In above, we saw three starters for effective starting of i. Stator voltage control of induction motor electrical.
Speed of a 3 phase induction motor can be controlled by these methods. Variable voltage variable frequency speed control of. Nehrir, speed control of threephase induction motor by stator voltage control ieee transactions on industrial electronics and control instrumentatio n, may 1975. 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.
The salient features of stator voltage control method are. Torque production is governed by the angle formed between the rotor and the stator magnetic fluxes. Stator voltage control is a method used to control the speed of an induction motor. So obviously the speed of an induction motor can be controlled by varying any of three factors namely supply frequency f, number of pole p or slip s. Numerous low power motor speed controls using simple voltage control are already in use and currently more efficient controls formotors in the thousands.
The speed of a 3 phase induction motor can be varied by varying the supply voltage. An induction motor can therefore be made without electrical connections to the rotor. However, reducing the stator voltage reduces simultaneously with the speed and the torque of the motor, which in many applications is undesirable. If the induction motor is operating in the linear magnetic region, the lm is constant. You should also make a dc measurement of stator winding linetoline resistance using a dmm. An843, speed control of 3phase induction motor using. The torque generated in the rotor of a 3phase induction motor is proportional to the flux generated by each stator pole, the rotor current and the power factor of the rotor. A modified approach to induction motor stator voltage and.
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. Stator current characteristics for uncontrolled induction motor. The singlephase induction motor is more subtle and less efficient. Hence, the synchronous speed changes with change in supply frequency. The synchronous speed and therefore, the speed of the motor can be controlled by varying the supply frequency. It is a 16 bit highperformance digital signal controller dsc. Line voltage control the torque developed varies with the square of the applied voltage. In the vhz control, the speed of induction motor is controlled by the.
Speed control of induction motor is possible in two sides. The output torque of the three phase induction motor is directly proportional to square of supply voltage for a given slip. Control the rotor speed in an asynchronous machine asm drive using the scalar vf control method. The synchronous speed of an induction motor is given by the relation shown below. Stator voltage control of an induction motor circuit globe. 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. The speed control of three phase induction motor is done by stator voltage control. Stator voltage control is basically a method to control the speed of an induction motor. As a voltage and a current is applied to the stator winding terminals, a magnetic field is developed in the windings. The 3phase set of currents, each of equal magnitude and with a phase. The mathematical model of a double cage induction machine is proposed. Other than this illustration of vector control strategy for an induction motor im drive using sinusoidal pulse width modulation technique has been efficient. Therefore by changing the number of poles we can easily change the speed of three phase induction motor.
There are many different methods and starter available to start the motor out of which dol direct online starter is very simple and cheap. Control of induction motor is complicated due to the control of decoupled torque and flux producing components of the stator phase currents. Conventional stator voltage control circuit for a three phase induction motor. Input and output voltage waveforms for 3phase pwm inverter. The magnetic field in the air gap from the voltage applied to the stator. Ac induction motor volts per hertz control with speed closed loop, driven by etpu on mpc5500, rev. Initially, when the motor is started, heavy current flows through the field winding of the stator because back emf has not yet been induced. Optimal control of induction motor using high performance. Stator voltage control frequency control stator voltage and frequency control i.
In this method of speed control of three phase induction motor rheostat is added in the stator circuit due to this voltage gets dropped. There is no direct access to the rotor quantities such as rotor fluxes and currents. Speed control of three phase induction motor electrical4u. Stator voltage control of an induction motor stator voltage control is a method used to control the speed of an induction motor. In slip ring induction motor, we can add external resistance in rotor circuit through. The speed of induction motor is changed from both stator and rotor side.
How an induction motor works by equations and physics. 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. This paper presents design and analysis of a three phase induction motor drive using igbt. This 3 phase motor is also called as an asynchronous motor. The speed of a three phase induction motor can be varied by varying the supply voltage. Induction motor has low inherent starting torque draw large starting currents, typically 68 x their full load values speeds not easily controlled as dc motors operate with a poor lagging power factor when lightly loaded induction motor components an induction motor has two main parts. Study of stator voltage control method for induction motor torque control using matlab simulation. Ac induction motor volts per hertz control with 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. In this control method, since the output torque is proportional to the slip.
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