When power supply for the stator is switched on, an alternating current flows through the stator winding. How an induction motor works by equations and physics. The works of the stator is common in all motor to develop a magnetic field. Wound rotor induction motors chapter ac motors pdf version.
In wound rotor induction motor, the rotor has a 3 phase winding similar to stator winding. Pdf this paper investigates wound rotor induction machine torque and. Slip ring induction motor is also known as wound rotor induction motor. 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 wound rotor with sliprings. Squirrel cage induction motor is used in lathes, drilling machine, fan, blower printing machines etc. This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors.
The merit of using wound rotor induction motor is to control speedtorque characteristics by inserting external resistance. In alternator rotor serves as rotating magnetic flux source and in motor it serves as source rotating mechanical force or torque. What is the advantage and disadvantage of rotor resistance. In repulsion motors the stator windings are connected directly to. Motors employing this type of rotor are widely known as phase wound motors or wound motor or slipring motors. Another type is squirrel cage motor that has no wire winding and has no slip rings. Controlling the rotor resistance allows for controlling the starting current, the speed, and the torque.
This work is introducing the designing of new three phase squirrel cage induction motor with an objective of getting good efficiency. Their sole purpose is to allow resistance to be placed in series with the. The stator frame consists of laminations of silicon steel, usually with a thickness of about 0. By far the most commonly used ac motor is the induction motor. Stator winding can be either star or delta connected depending upon the design. Why the revolving speed of the induction motor is lower than the rated value. The benefit of a wound rotor motor is that the resistance of the rotor circuit can be externally varied, to provide either variable resis tance in the case of a liquid rheostat or steps when a series of external resistors of fixed resistance are used, to maximize the torque to suit a particular application. By combining the mechanical equation of motor and the. Pdf starting of a threephase induction motor using a starter rheostat in rotor circuit has some disadvantages. Pdf modeling and vector control of threephase induction. Type of induction motor for ac in which the rotor has wire winding. Dont worry, difference between squirrel cage and slip ring type induction motor is tabulated after the figure. Long motor life is ensured with the use of external resistor banks or liquid rheostats that dissipate heat buildup generated during motor startup. Pdf matlab examples design of wound rotor induction.
Wound rotor motors also can develop high starting torque at standstill while maintaining low inrush. Woundrotor induction generators wrigs have been built for power per unit as high as 400 mwunit. Learn more about the construction and operation of a slip ring induction motor. It also defines the running thermal capability, thermal limit curve, accelerating thermal limit and locked rotor thermal. What makes the wound rotor motor a unique induction machine is its rotor. Difference between squirrel cage and slip ring induction. Squirrel cage wound rotor with slip rings the rotating magnetic field. If the motor has six leads 3 mains and 3 neutrals, the three phase should be connected into one series circuit. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor.
Squirrelcage rotor almost 90 per cent of induction motors are squirrelcage type, because this type of rotor has the. Wound rotor induction motor wrim speed torque curves, 282016. They are commonly used on fans, pumps, conveyors and crane systems. The motor mode is required in applications such as pump storage power plants or even with. The figure itself depicts many difference between the two types of motors. Adjusting the resistance allows control of the speedtorque characteristic of the motor. A woundrotor motor is a type of induction motor where the rotor windings are connected through slip rings to external resistance. Since the slip of an induction motor increases as the rotor resistance increases, some speed control is possible using a wound rotor motor and varying the rotor resistance while running. Almost 90 percentage of induction motors are squirrelcage type, because this type of rotor has the simplest and most rugged construction imaginable and is almost indestructible. With indian and international standards almost similar for the induction motors, squirrel cage or wound rotor, the replacement is extremely easy and fast reducing downtime of outage, which is vital for sustaining. Pdf a new soft starting method for woundrotor induction motor. Winding rotor arrangements for 3 phase induction machine three phase slip ring induction motor a wound rotor or slip ring motor has a 3phase winding, similar to the stator winding. Control of motor characteristics by squirrelcage rotor design.
No comparable standard exits for wound rotor induction or synchronous motors. But the rotor construction differs with respect to the type of motor. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. A three phase induction motor has 3 phase stator winding where supply is given. Wound rotor induction motor the engineering projects. Variable speed generators woundrotor induction generators. Rotors of induction motors are of two types, the squirrel cage and the wound rotor. In this case, one phase will carry the full applied current and each of the others, onehalf each. That current in turn produces a field that interacts with the environment to drive the rotor. The stator of slip ring induction motor is very much the same as that of the squirrel cage induction motor, but the construction of its rotor is very much different. A motor rating of 10 horse power, 415 volts with 1440 rpm and 4pole is selected for design problem and an equivalent circuit model is developed to find out the various. A major difference between the wound rotor motor and the squirrel cage rotor is that.
In the induction motors used in lift and hoists, you will see a type of rotor called a slip ring rotor, whereas in most of. In this type of three phase induction motor the rotor is wound for the same number of. Wound rotor induction motors ac motors electronics. 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 woundrotor with sliprings. Repulsion motors are classified under single phase motors.
Please have a look at the below figures of squirrel cage induction and wound rotor slip ring induction motor. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. The rotor will constantly be turning to align its magnetic field with the stator field. The slip ring of the wound rotor induction motor has bad contact. Designing of three phase squirrel cage induction motor for. Modify the surface of the slip ring and regulate the pressure of the carbon brush. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting. Wound rotor tecowestinghouse motor company, a world. Wound rotor motors deliver speed control of heavy and hightorque loads.
Controllers for wound rotor motors include for the stator the same protection and switching functions that are used for squirrel cage motors. The basic idea of an electric motor is to generate two magnetic fields. A torquespeed characteristic curve combining highresistance effects at low. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrelcage rotor. This article is devoted to slip ring induction motors. Article pdf available in the journal of engineering may 2014 with 919 reads. The induction motors are simple and of rugged design, low maintenance, low cost and most suitable means for such applications. Laminations from typical squirrelcage induction motor rotors, showing the cross. A wound rotor induction motor has a stator like the squirrel cage induction motor. If the motor has only three leads, two must be connected together to form one circuit through the winding. Speed control of wound rotor induction motor pdf objective.
Modeling and vector control of threephase induction motor when two phases of the stator are open circuit. Rotor is rotating part of any electrical machine like alternator, motor. Wound rotor induction generator shortcircuit fault classification using a new neural network based on digital data article september 2011 with 41 reads how we measure reads. As induction motors are widely used, we will present the cheaper technique to control these motors. Electric motor construction of induction motors britannica. Comparative power quality study of variable speed wind turbines. Instead the rotor is wound with shorted turns in which the environmental field induces a current. The threephase induction motor is the easiest motor of this type to understand so these notes start with that type. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. The stationary part of the motor is called stator and rotary part of the motor is called rotor. Electric motor electric motor construction of induction motors. Motors employing this type of rotor are variously known as phase wound motors or wound motors or as slipring motors.
Wound rotor induction motor wrim speed torque curves, 2. Hence the utility of wound rotor induction motor has also been increased on par with. It also provides a way to recover the power generated by the increased slip by converting the slip energy to. Speed control of wound rotor induction motor using rotor. Woundrotor motors can be started with low inrush current, by inserting high resistance into. Induction motors have been ruling the industrial world for many decades. A repulsion motor is a type of electric motor which runs on alternating current ac. The polyphase induction motor the polyphase induction motor is the most commonly used industrial motor, finding application in many situations where speed regulation is not essential. Induction motors mainly consists of two types rotors which are wound rotor and squirrel cage rotor with similar stator construction. Slip ring induction motor fundamentals pnpntransistor. Consider a single phase induction motor whose rotor is at rest. Active and reactive power control of wound rotor induction.
Initial start up testing of 1915 vintage 750 hp wound rotor motor. The motors are rated according to their primary and secondary windings. In recent advancements in electric machine and drives, wound rotor motor is extensively used. The construction of stator of the induction motor is almost the same as other motors. Rotor induction motor at noload and fullload to observe speed control using an. Three phase slip ring induction motor my tech info. Comparative power quality study of variable speed wind. Selection of induction motors for industrial applications. A wound rotor induction motor has a stator like the squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. This document was uploaded by user and they confirmed. Post glover wound rotor motor resistors wound rotor motors, as opposed to ac induction motors, generate the same torque in both forward and reverse.
A wound rotor induction motor is also known as slip ring induction motor. Instead of a series of rotor bars, a set of insulated rotor coils is used to accept external impedances. The winding is placed evenly on slots of the rotor. Lamination is necessary since a voltage is induced along the axial length of the steel as well as in the stator conductors. It was formerly used as a traction motor for electric trains e. These three increased losses combine to increase the in put for a given. Induction motors combine outstanding performance with an advanced longlife design. I will tell you about the construction of wound rotor induction motor in the first section.
The rotor winding terminals are connected to three slip rings which turn with the rotor. Pdf investigation of wound rotor induction machine vibration. In the second section, i would be throwing light on the operation and working principle of wound rotor induction motor. It is simple and relatively inexpensive, and the absence of sliding contacts in the squirrelcage machine reduces maintenance to a minimum. Induction machines are also known as asynchronous machines, that is, they rotate below synchronous speed when used as a motor and above its synchronous. Although induction motors, specifically, squirrel cage types are widely used in electrical drives, wound rotor induction motor wrim has some distinct applications like high torque, starting with high inertia loads, adjustable speed drives and soft starts. Calculate the main dimensions, turns per phase, number of slots,number of conductors, cross section and slot area of a 250 h. In the case of a squirrel cage induction motor, the rotor is inaccessible and rotor circuit resistance is xed, whereas the wound. This type of 3phase induction motor has high starting torque, which makes it ideal for applications where standard nema design motors fall short. The wound rotor motor is particularly effective in applications where using a squirrelcage motor may result in a. This article will highlight the important concepts for wound rotor motors that must be understood before purchasing one of these but know it is not allinclusive.
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