Due to high input frequency from laboratory supply, the analysis of power loss made by hysteresis and eddy current become very important. The speed control through vf drive is the best method. Squirrel cage induction motor an overview sciencedirect. There are more than one methods to control the speed of induction motor, you can choose one depending on your resources, efficiency required etc. A 1phase induction motor is similar to a 3phase squirrel cage induction motor in physical appearance. A 3 phase induction motor can be used for different applications with various speed and load requirements. Know about the different winding slots, lamination of the stator and its construction. A repulsion induction motor is a form of repulsion motor that has a squirrel cage winding in the rotor in addition to the repulsion motor winding. Explain starting methods of 3 phase induction motor. Speed control methods of induction motor by kiran daware ac machines, induction motor 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.
This makes constant vf the most common speed control of an induction motor 1. A motor of this type may have either a constant speed see mg11. Speed control works well with variable speed loads like elevators and printing presses. These motors fill most generalpurpose, constant speed drive requirements. Speed control of wound rotor induction motor using rotor. At base speed, the voltage and frequency reach at the rated values. Methods of speed control of induction motor electrical. Methods of speed control of induction motor electrical concepts.
In order to understand the speed control, theory and methods, it is important that the basic theory of the controlled component i. This design is directly applicable to a 4 kva, 3phase, induction machine. Pdf speed control of squirrel cage induction motor sqim. The slip ring motor has very little application in industries. Torquespeed characteristics of three phase squirrel cage. The stator construction is the same in both motors. This motor should be mounted on the motor bench, wherein the motor shaft may be coupled to the dynamometer for taking the measurements. Design of a speed controller for a squirrelcage induction motor. An induction motor can therefore be made without electrical connections to the rotor.
The frequency can be varied using a manual input to the controller. The speed control can be achieved through two modes of vfd operation. The reason for the name squirrel cage is because of the type of rotor used in these motors. This is because the squirrel cage motor has a simple and rugged construction. Also lets get to know the methods which are used to control the speed of squirrel cage. Pdf speed control of squirrel cage induction motor sqim based.
Modelling and analysis of squirrel cage induction motor with leading reactive power injection 101 accommodate a system with any number of phases which might be useful in the case of the machine having an auxiliary winding as proposed in this work. Design of speed controller for squirrelcage induction motor. Know how the speed control is easily achieved by changing the number of stator poles. Oct 04, 2017 the speed torque curve of an induction motor can be modified by an armature winding reconnected to give different sets of poles. A squirrel cage induction motor therefore draws a very high starting. This method of speed control can only be applied to squirrel cage motor. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. We previously described a squirrel cage induction motor acting as a.
The above three methods are most commonly used for the speed control of squirrel cage induction motors. What is a squirrel cage motor and how does it work. A 3 phase ac induction motor photoed by hordu motor. Section 2 presents internal dynamics of the induction motor in state space form. Speed control of induction motors the speed of an induction motor is given as n 120fp 1s.
While there are different methods for control, variable voltage variable frequency vvvf or v f is the most common method of speed control in open loop. Pdf methods for varying speed in squirrel cage induction. Notice and disclaimer the information in this publication was considered technically sound by a consensus among persons engaged in its development at the time it was approved. The induction motor is started by itself that we know. Out of all the electrical machines, induction motor is the most used machine in industries. Some of the main advantages, why you should go for this motor include the following. Our article all about induction motors explains the specifications for all types of induction motors and is a good place to see all the different induction motor characteristics. Wound rotor induction motors ac motors electronics. Pdf speed control of three phase squirrel cage 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.
This article will focus on what needs to be specified for squirrel cage induction motors, which involves phase, speed, torque, and current. The speed torque curve of an induction motor can be modified by an armature winding reconnected to give different sets of poles. But at the starting of the induction motor, starting current is very large which may damage motor windings. Three phase squirrel cage induction motor in order to understand the speed control, theory and methods, it is important that the basic theory of the controlled component i. Jul 25, 2019 squirrel cage induction motor working principle. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. Control of motorcharacteristics by squirrel cage rotordesign the reactance x2 in an induction motor equivalent circuit represents the referred form of the rotors leakage reactance. In ac rotating machine speed of machine is govern by the equation n120fp. Also appreciate the rugged construction of squirrel cage rotor and know the spectacular reasons for the skewed arrangements of the rotor conductors.
Methods for varying speed in squirrel cage induction motors. One motor is the called the main motor, and another motor is called the auxiliary motor. Squirrel cage induction motor and wound rotor induction motor. An843, speed control of 3phase induction motor using pic18 mcus.
When the number of poles changes, so does the speed. There is uniform air gap between stator and rotor but no electrical connection between them. Torquespeed characteristics of squirrel cage induction motor iitbee. The squirrel cage induction motor drive with vector or fieldoriented control offers a high level of dynamics performance and the closedloop control associated with this derive provides the longterm stability of the system. Induction motor drives are used in a multitude of industrial and process control applications. Torque speed characteristics of induction motor slip. The most popular type is the 3phase, squirrel cage ac induction motor. The threephase squirrel cage induction motor can, and many times does, have the same armature stator winding as the threephase synchronous motor. The ruggedness and simplicity of the squirrel cage induction motor usually makes it the first choice for a driver. Squirrel cage motor almost 90% of induction motors are squirrel cage motors.
Hence, the synchronous speed changes with change in supply frequency. How to control the speed of an induction motor quora. This method is generally used for squirrel cage induction motors, as squirrel cage rotor adapts itself for any number of stator poles. This rotating magnetic field has a speed which is known as the synchronous speed. Speed control of three phase squirrel cage induction motor ijert. The rotor is same as that employed in 3phase squirrel cage induction motor. Speed control of induction motor 7 ways to control induction.
Very large motors sometimes have a portion of the ends of the rotor windings externally connected through brushes so you can control the effective resistance of the rotor. Recall that leakage reactance is the reactance due to the rotor flux lines that do not also couple with the stator windings. More than 90% of motors used in industries are squirrel cage induction motor due to its rugged and maintenance free design. The change in the number of stator poles can be achieved by having two or more number of. This phenomenon is known as crawling of an induction motor and the speed is called as crawling speed. Torque speed characteristics of induction motor slip power. The synchronous speed of an induction motor is a function of the number of stator poles. A three phase induction motor is basically a constant speed motor so its somewhat difficult to control its speed. Control of motorcharacteristics by squirrelcage rotordesign the reactance x2 in an induction motor equivalent circuit represents the referred form of the rotors leakage reactance.
A squirrelcage rotor is the rotating part of the common squirrel cage induction motor. Solid state speed control of a squirrelcage induction motor. Control of motorcharacteristics by squirrelcage rotordesign. In a motor control, a voltage saturation is a serious problem as a motor speed increases. In this method of speed control of three phase induction motor, the two threephase induction motors are connected on a common shaft and hence called cascaded motor. In operation, the nonrotating stator winding is connected to an alternating current power source. The operating point is the intersection of the two characteristics and we can fix for a given load and motor parameters. Firstly, i am going to tell you about the structure of squirrel cage induction motor. This type of speed control is only possible for slip ring induction motor.
Working principle of 3 phase squirrel cage induction motor. The implementation is done using a rectifier and an inverter, where the pwm triggering pulses were generated by using pic micro controller for switching the igbts of the inverter. Require less maintenance as there are no slip rings or brushes good speed regulation they are able to maintain a constant speed high efficiency in converting electrical energy to. An induction motor s rotor can be either wound type or squirrel cage type. It may be used where, the induction motor is supplied by a dedicated generator so that frequency can be easily varied by changing the speed of prime mover. This method is most suitable for applica tions without position control requirements or the need for high accuracy of speed control. Advantages of three phase squirrel cage induction motor. It is increasingly common practice to use 3phase squirrel cage ac induction motors with variable voltage variable frequency vvvf converters for variable speed drive vsd applications. Former is cheaper and broadly used as it requires less maintenance than later one.
Pdf in a motor control, voltage saturation is a serious problem as a motor speed increases. Pdf methods for varying speed in squirrel cage induction motors. Physical layout of induction motor in an induction motor induction refers the field in the rotor is induced by the stator currents and asynchronous refers that the rotor speed is not equal to the stator speed. The speed control of induction motor is done at the cost of decrease in efficiency and low electrical power factor. Speed control of wound rotor induction motor using rotor resistance control aim to use variable resistance in the rotor circuit to control wound rotor induction motor speed theory polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith sliprings. The fig 1 shows the relationship between the voltage versus frequency. Typically, the fullload slip for the squirrel cage induction motor is less than 5%. To solve the problem, various field weakening methods were studied for a long time. This paper analyzes the concepts of a wellbalanced capacitor voltage fed multilevel diode clamped converter driving a three phase squirrel cage induction motor at a varying load. Speed control of three phase squirrel cage induction motor. As in the synchronous motor, applying threephase currents to the armature creates a synchronously rotating magnetic field. The voltage and frequency being increased up to base speed. Speed control of a three phase alternating current. Information guide for general purpose industrial ac small.
Pdf speed control of induction motors kamakhya basumatary. Which is the best method of speed control of a squirrel. Fieldoriented control foc is a technique whereby the complex nonlinear structure of a squirrelcage induction machine scim can be controlled to behave in. Variable voltage variable frequency vf control theory an induction motor compared to a dc motor has some major advantages such as. Dec 17, 2019 this method cannot be used for squirrel cage induction motor. Oct 09, 2016 a 3 phase induction motor has two types based on the rotor construction, named as.
It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Starting of squirrel cage induction motors485 an induction motor can be regarded as a transformer with a small air gap in the magnetic circuit. Pdf speed control of a squirrel cage induction motor. However, with variable frequency drives, these disadvantages can be overcome. The design of the basic inverter is covered in chapter 2. Induction motor control is complex due to its nonlinear characteristics.
The induction motor rotor is a completely shortcircuited conductive cage. Thus it is obvious that to change speed of machine any one parameter either frequency or no of poles are to be changed. Some advantages of squirrel cage induction motors are. Generally an induction motor operates at almost constant speed as the load is varied. The type of connection decides the permissible loading at constant torque or constant power. This method is suitable for squirrel cage motors as their rotors can. These are some of the methods which are commonly used for the speed control of squirrel cage induction motors. How an induction motor works by equations and physics.
Construction of squirrel cage induction motor explained. The paper describes the open loop control of the 3 phase induction motor at variable speed using a 3 phase inverter. High speed im with appropriate squirrel cage can reach circumferential speed up to 200 ms, see in 2. Induction motor types based on the construction of the rotor, induction motors are broadly classified in two categories. This speed control technique is only useful over a range of 50% to 100% of full speed.
Speed control of induction motor detailed explanation. Its synchronous speed with a 50 hz supply is therefore 60 fp, or 1500 rpm. This method cannot be used for squirrel cage induction motor. Why is speed control in an induction motor, difficult. The stator winding is assumed to be yconnected with the access to the phase terminals. A three phase squirrel cage induction motor rated at 3 horsepower, 220 v, 60 hz, 1725 rp m is fed by a three phase mosfet two level inverter. Our test motor with squirrel cage has a circumferential speed of 40 ms. In ac induction motor control when the upper switch is switched on i.
Speed control of three phase squirrel cage induction motor using vf method is implemented. For a fullload operating slip of 3 per cent, the speed will then be 1 s60 fp, or 1455 rpm. Normally, we use the motors in industrial drives because they are rugged, reliable and economical. In normal conditions, the slip ring motor functions like a squirrel cage motor.
This is why the commonest induction motors are called squirrel cage motors since the structure looks like what might be used to entertain a small animal in captivity. The reliability of squirrel cage ac induction motors, compared to dc motors, is high. When the 3 phase supply is provided to the stator, a magnetic field is produced which rotates the rotor and motor starts. Squirrel cage induction motors have poor starting torque and high starting currents. Read more methods of speed control of induction motor. The squirrel cage induction motor is the most commonly used motor in industry. The main methods employed for speed control of induction motors are as follows. Speed control of squirrel cage induction motor sqim based on voltage angle. The typical base speed of the four pole induction motor varies between 1420 and 1480 rpm at 50 hz, while the synchronous speed is 1500 rpm at 50 hz. Mar 09, 2018 external resistance can be connected to the rotor circuit to control the motor speed. To obtain the torquespeed characteristics tnr of a three phase squirrel cage induction motor using. Now let us discuss in detail, the most common form of induction motor, the squirrel cage induction motor. Almost 90% of induction motors are squirrel cage motors. An843, speed control of 3phase induction motor using.
Squirrel cage wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. The typical base speed of the four pole induction motor varies between 1420 and 1480 rpm at 50 hz, while the synchronous speed. Require less maintenance as there are no slip rings or brushes good speed regulation they are able to maintain a constant speed high efficiency in converting electrical energy to mechanical energy while running, not during startup. In section 3, the different speed control techniques of an ac motor are discussed. The only parts of the squirrel cage motor that can wear are the bearings. Modelling and analysis of squirrel cage induction motor. The rotor of the squirrel cage three phase induction motor is cylindrical in shape and have slots on its periphery. External resistance can be connected to the rotor circuit to control the motor speed. Jun 05, 2018 out of all the electrical machines, induction motor is the most used machine in industries.
We can add external resistance in rotor circuit through a slip ring in the induction motor. Actual speed of an induction motor is given as n ns 1 s. Speed control of three phase induction motor electrical4u. Torque speed characteristics of three phase squirrel cage induction motor aim to obtain the torque speed characteristics tn r of a three phase squirrel cage induction motor using 1. The main disadvantage of squirrel cage induction motor is poor speed control and low starting torque. Threephase squirrel cage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. Speed control of induction motor using vf technique phase i a thesis. The actual fullload slip of a particular motor is dependant on the motor design. This type of speed control is not possible for the squirrel cage induction motor. In slip ring induction motor slip rings are provided with the rotor.
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