# Nslip in induction motor pdf filetype

The emf induces in the rotor because of the relative motion, or we can say the slip speed of the motor. This minimum is equal to the magnetising current which is needed to create flux in the machine. Induction motor is an ac electric motor, having a stator and a rotor just like other motors, but the working principle is a little different which would be discussed further. Induction motors p3 typical torquespeed and powerspeed curves for a 4pole induction motor torque power p these curves are greatly affected by the rotor resistance r2 in our model.

If the motor slip is known, the rotor speed can be expressed by the equation. So, the rotor current is directly proportional to the induced emf. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Introduction to induction motor the engineering projects. Why we need to start induction motor using a starter or with one of starting methods. Per phase equivalent circuit of induction motor to determine expressions for torque and power, the equivalent circuit in fig. Induction motors horizontal and vertical weg electric machinery, wem, induction motors have been specifically designed and manufactured for the most severe industrial applications, such as heavy duty fans, pumps, refiners, compressors, crushers and grinding mill drives.

General purpose slipring induction motors cantoni motor pdf. The circuit impedances are defined in ohms by the following. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. At another of the lab benches, your instructor has set up the induction motor drive system as shown above. If the 3phase slip ring induction motor is started as a normal motor with the slip rings shorted, due to low starting torque of slip ring motor, the motor will draw high current i. You should also make a dc measurement of stator winding linetoline resistance using a dmm. The motor speed is a function of its rotor resistance. This slip must be present, even when operating in a fieldoriented. In practice, an ac induction motor is an asynchronous motor in which the rotor lags field speed so its rotor must spin more slowly than the field, or slip. Consult cantoni motors entire general purpose slipring induction motors catalogue on directindustry. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. The load test on induction motor is performed to compute its complete performance i. Learn more about the construction and operation of a.

As we know, the slip speed is the difference between the synchronous and rotor speed of the induction motor. The good power factor of an induction motor can be achieved if the average flux density in the air gap is a absent b small c large d infinity ans. Possibility of adding additional resistance to control speed. What is the working principle of slip ring induction motor. Because it is a capacitortype induction motor, it has a high power factor and runs with a low noise level caution. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. In the rotor resistance control method, the slip power in the rotor circuit is wasted as i 2 r losses during the lowspeed operation. This article is devoted to slip ring induction motors. How can direction of rotation of 3 phase induction motor. When selecting a 3phase induction motor for an application several motor types can fill the need manufactures often specify the motor class best suited to drive the load 3phase induction motors under 500 hp are standardized the frames have standard dimensions a 25 hp, 1725 rpm, 60 hz motor from one manufacture can be. The alternating current ac induction motor is often referred to as the workhorse of the industry because it offers users simple, rugged construction, easy maintenance and costeffective pricing. Sep 27, 2016 induction motor is an ac electric motor, having a stator and a rotor just like other motors, but the working principle is a little different which would be discussed further. Squirrel cage rotor ac induction motor cutaway view. The induction machine operates between synchronous speed slip 0 and double value of the synchronous speed slip 1.

Therefore stop the induction motor once, change the wire connections and make a reverse run. Figure shows the disassembled view of an induction motor with squirrel cage rotor. For an induction motor with p polesand f frequency, slip for induction motors a very important parameter is the slip of the motor the slip, s, defines the relative speed difference between synchronous speed and rotor speed and is given by. The torquespeed characteristic of an induction motor can be significantly changed by designing. Slip ring induction motor are used where high starting torque is required i. The torque produced by the induction motor is directly proportional to induction motor slip. Slip in electrical induction motors engineering toolbox. The value of slip in induction motor is can never be zero. An induction motor can therefore be made without electrical connections to the rotor.

The catalogue covers slipring induction motors called also wound rotor induction motors that are applied to start a high inertia load or a load that requires a very. The induction motor is made up of the stator, or stationary windings, and the rotor. This is evident from the equivalent circuit shown in fig. Portland slip ring induction motorsbrush holder problems. The starting of threephase wound rotor induction motors by stepped resistances added in the rotor circuit suffers from several problems.

Induction motor protection system circuit and its working. The induction motor cannot make a quickreversal run because of the torque acting in the opposite therefore stop the induction motor once, change the wire connections and make a reverse run construction characteristics coding system motor ac power supply mounting frame option d2 l a 4. The induction motor is an essential device in various industrial applications. Motors and drives ac induction motor slip what it is and. Learn more about the construction and operation of a slip ring induction motor. The singlephase ac induction motor best fits this description. That is why such motors are known as induction motors. What is common to all the members of this family is that the basic physical process involved in their operation is the conversion of electromagnetic energy to mechanical energy, and vice versa. U, electrical engineering department abstract rotating electrical machines play an important role in the worlds industry. The absence of slip ring and brushes make the construction of single phase.

Threephase induction motors with slip ring rotor in the ic 411 cooling class are also designated as ribcooled motors. Speed control of wound rotor induction motor using rotor. This method is also known as static scherbius drive. The stator is composed of laminations of highgrade sheet steel. Electromagnetic analysis of induction motor using fem. Starting, braking and positioning with threephase cage. The cooling can be integrated so that the induction motor can work in a hermetically sealed environment for instance under water. It is logical that the least expensive, lowest maintenance type. The basic idea of an electric motor is to generate two magnetic fields. As with other electrical machines, an equivalent electric circuit can be developed for the purpose of gaining insight into the motors operation. The 3phase set of currents, each of equal magnitude and with a phase.

The induction machine operates between zero speed slip 1 and synchronous speed slip 0. Number of poles, frequencies and synchronous induction motor speed. Record all nameplate information for the induction motor. April 11, 20 6 of 10 the impedances of the circuits shown in figure 5 are found from noload and blockedrotor tests.

The summation of all torques acting on the motor shaft comprises the mechanical model. Lecture 6 three phase induction motors cairo university. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Electromagnetic analysis of induction motor using fem 1bhagat komal vipinchandra 2. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. Currentspeed curve of an induction motor it is a vshaped curve having a minimum value at synchronous speed. Singlephase induction motor threephase induction motor singlephase induction motor there are probably more singlephase ac induction motors in use today than the total of all the other types put together. It is logical that the least expensive, lowest maintenance type motor should be used most often. 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. The rotor will constantly be turning to align its magnetic field with that of the stator field. Three phase slip ring induction motor my tech info. In fact, an induction motor can be treated as a rotating transformer i. What is common to all the members of this family is that the basic physical process involved in their operation is the conversion of electromagnetic energy. Motor analysis block diagram induction motor starting can be analyzed using electrical, mechanical, and thermal models which interact as diagrammed in figure 1.

Connected between the variable frequency drive and the induction motor windings, your instructor will have inserted a power analyzer. Let the phase sequence of the threephase voltage applied to the stator winding is. Applications of single phase induction motor these are used in low power. Induction motors are popularly used in the industry focus on threephase induction motor main features. Advantages of slip ring induction motor it has high starting torque and low starting current. Induction motor driving a centrifugal compressor advantages. Construction of three phase induction motor electrical4u.

Slip, which varies from zero at synchronous speed and 1 when the rotor is at rest. This work presents a symmetrical v connected twophase induction motor with windings displaced by. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. There are two types of induction motors, one with wound type rotor, also called slip ring motor and another one with squirrelcage rotor. The perphase equivalent circuit of an induction motor is shown in figure 1. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. The page also answers why single phase induction motor is not. There are two types of induction motors, one is named as single phase induction motor, while the second one is named as 3 phase induction motor. Slip energy recovery of an induction motor circuit globe. Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. The induction motor doesnt use a combustion process to deliver power so there is no need to refuel or air.

A wide variety of low speed induction motor options are available to you, such as home appliance, car. There are two major components of an ac induction motor. Jun 01, 2018 slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. Since flux is purposely kept constant, it means that magnetising current is the same at all synchronous speeds. Induction motor introduction an induction motor is an alternating current motor in which the primary winding on one member usually the stator is connected to the power source and a secondary winding or a squirrelcage secondary winding on the other member usually the rotor carries the induced current.

Sensorless field oriented control of 3phase induction motors. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. The induction motor cannot make a quickreversal run because of the torque acting in the opposite direction. Almost 80% of the mechanical power used by industries is provided by three phase induction motors because of its simple and rugged construction, low cost, good operating characteristics, the absence of commutator and good speed regulation. These motors work on 3phase supply and a standard temperature to keep the loads at preferred conditions. The corresponding performance curves are plotted when selecting torquesee generator. This paper suggests a novel method of motor starting by. In the electrical model, the voltage, v, and the slip, s, determine the rotor current. The difference, or slip, between actual and synchronous speed varies from about 0. The three phase induction motor is the most widely used electrical motor. Starting and speed control of 3phase slipring induction. Full descriptions of the circuits and the tests are found in reference 1.

The dissipated heat generated in the motor is output to the motor housing and is discharged by the cooling air of the external fan via the cooling fins. Section 5 threephase induction motors by hashem oraee pdf. 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. By far the most commonly used ac motor is the induction motor. Lower startup torque higher startup current low r2 n. Induction motor introduction an induction motor is an alternating current motor in which the primary winding on one member usually the stator is connected to the power source and a secondary winding or a squirrelcage secondary winding on the other. Slip of induction motor plays an important role in the operation of the induction motor. The induction motor can be made easily and with that the price is rather low compared with other technologies.

The direction of rotation of a 3 phase induction motor can be reversed by interchanging any two of the three motor supply lines. The alternating current ac induction motor is one of the most rugged and most widely used machines in industry. Threephase induction motor singlephase induction motor there are probably more singlephase ac induction motors in use today than the total of all the other types put together. 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.

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