If the slip motor is started with all the slip rings or the rotor terminals shorted, like a normal induction motor, then it suffers extremely high locked rotor current, ranging up to 1400%, accompanied with very low locked rotor torque as low as 60%. Wound rotor induction motors ac motors electronics textbook. The singlephase induction motor is a kind of ac motor made with a starting winding added at right angles to the main stators winding. A special type of ac induction motor, known as wound rotor motors, will be. These machines are different from the squirrel cage induction motor in that the rotor is wound, and the end of the windings brought out to slip rings. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. The wound rotor induction machine is capable of electromechanical energy conversion, if the stator and rotor windings are connected in series with a proper phase sequence. Resistance outside the rotor affects the torque speed. Principle of operation of induction motor eeeguide. Thus, around 1900 the induction motor was ready for wide industrial use. Polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith sliprings. The rotor, mounted on a shaft, is a hollow laminated core having slots on its outer periphery.
Basic design and theory of operation the alternating current ac induction motor is one of the most rugged and most widely used machines in industry. It is called a squirrel cage motor because the rotor inside of it known as a squirrel cage rotor looks like a squirrel cage. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrelcage rotor. The rotor winding terminals are connected to three slip rings which turn with the rotor. Squirrel cage induction motor is used in lathes, drilling machine, fan, blower printing machines etc. Sep 18, 2018 induction motors have been ruling the industrial world for many decades. An induction motor can therefore be made without electrical connections to the rotor. Wound rotor motors deliver speed control of heavy and hightorque loads. It is not advised to start a slip ring induction motor with its rotor terminals shorted. It also provides a way to recover the power generated by the increased slip by converting the slip energy to. Slip ring motor fundamentals brighthub engineering. In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. Synchronous and asynchronous electricmotors the electric motor is an electromechanical continuous energy conversion equipment that converts electrical energy into electrical energy mechanical energy. Typical wound rotor induction motor the downside of the slip ring motor is that slip rings and brush assemblies need regular maintenance, which is a cost not applicable to the standard cage motor.
The rotor of the slip ring induction motor is also cylindrical or constructed of lamination. Adjusting the resistance allows control of the speedtorque characteristic of the motor. Wound rotor induction motor the engineering projects. What is the advantage and disadvantage of rotor resistance of. This work is introducing the designing of new three phase squirrel cage induction motor with an objective of getting good efficiency. The principle of operation of induction motor figure 9. They are inherently speed regulating machines, this being achieved by adding resistance to the rotor circuit via the slip rings. This article is devoted to slip ring induction motors. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. One type is called squirrel cage motor and the other is called wound rotor induction motor wrim.
In this type of three phase induction motor the rotor is wound for the same number of poles as that of stator but it has less. Threephase squirrelcage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. The rotor of the squirrel cage motor has no winding, and there is no need for the rotor to be electrically connected to any electricity. The rotor of the latter, however, as the name implies, has windings. Windingrotor 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. Asymmetrical operation of induction machine results in. The three phase induction motors are simple in construction, rugged, low cost and easy to maintain. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. Designing of three phase squirrel cage induction motor for. The winding placed in these slots called rotor winding may be one of the following two types. Squirrel cage induction motor an overview sciencedirect. This rotor is a cylinder of steel laminations, with highly.
For reason of economy, most houses, offices and also rural areas are supplied with single phase a. Jul 25, 2019 a 3 phase squirrel cage induction motor is a type of three phase induction motor which functions based on the principle of electromagnetism. The 3phase set of currents, each of equal magnitude and with a phase. I will tell you about the construction of wound rotor induction motor in the first section.
A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought. Woundrotor induction motor explain how this motor can be operated as either a synchronous motor or a plain 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. What makes the wound rotor motor a unique induction machine is its. The wound rotor motor is particularly effective in applications where using a squirrelcage motor may result in a starting current thats. If the rotor windings are shorted and a start is attempted i. Woundrotor induction motors need high starting torque. Controlling the rotor resistance allows for controlling the starting current, the speed, and the torque. Describe how a squirrel cage motor is built, and classify it as either an induction motor or a. Wound rotor tecowestinghouse motor company, a world leader. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. The rotor will constantly be turning to align its magnetic field with that of the stator field. Induction motors have been ruling the industrial world for many decades.
The induction motor is made up of the stator, or stationary windings, and the rotor. Rotor induction motor an overview sciencedirect topics. Power supply, dai, wound rotor induction motor 8231, electrodynamometer 8960, timing belt. This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. In the case of a squirrel cage induction motor, the rotor is inaccessible and rotor circuit resistance is xed, whereas the wound. Another important advantage over squirrelcage motors is higher starting torque. Jan 10, 2016 principle of operation of induction motor. 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. Wound rotor tecowestinghouse motor company, a world. Wound rotor induction motors ac motors electronics. In previous articles i have discussed the construction, operation, starting, speed control, and classes of squirrel cage induction motors. 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. In 1889, dolivodobrovolsky invented the induction motor with the wound rotor and subsequently the cage rotor in a topology very similar to that used today.
Wound rotor motors are also referred to as slip ring motors. Wound rotor induction motors with three rotor slip rings have been used in adjustable speed drives for many years. An induction motor s rotor can be either wound type or squirrelcage type. The basic idea of an electric motor is to generate two magnetic fields.
Instead of a series of rotor bars, a set of insulated rotor coils is used to accept external impedances. Oct 10, 2016 a wound rotor induction motor is also known as slip ring induction motor. Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound rotors having three windings each connected in star. In the second section, i would be throwing light on the operation and working principle of wound rotor induction motor. The stator is fed from a 3phase supply of voltage vphase and frequency f hz. The following safety and common symbols may be used in this manual and on the equipment. By far the most commonly used ac motor is the induction motor. In an induction motor, torque is equal to the power crossing the air gap divided by the synchronous mechanical speed. There are two basic reasons for the use of singlephase motors rather than 3phase motors. What makes the wound rotor motor a unique induction machine is its rotor.
Wound rotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. Wound rotor induction motors chapter ac motors pdf version. No wonder that before 1910, in europe, locomotives provided with induction. The stator of a wound rotor motor is the same as a typical induction motor, but the rotor has a three. The construction of slip ring induction motor is quite different compared to other. The rotor of an induction motor can be a squirrel cage rotor or wound. Their sole purpose is to allow resistance to be placed in series with the.
Speed control of wound rotor induction motor using rotor resistance. The anatomy and operation of these motors will be explored, as well as the. And in the previous article on types of electrical motors, we have classified induction motors based on the type of rotor used. Pdf performance analysis of wound rotor induction motor. A 460 v, 25hp, 60hz, fourpole, yconnected wound rotor induction motor has the following impedances in ohms per phase referred to the stator circuit. Construction of squirrel cage induction motor explained. There are two major components of an ac induction motor. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below.