Explain starting methods of 3 phase induction motor. What is major difference between a 3 phase induction motor and a single phase induction motor. If the speeds become equal, there would be no such relative speed, so no emf induced in the rotor, and no current would be flowing, and therefore no torque would be generated. The singlephase induction motor is much the same in construction as the threephase motor. Electrical motors are the machines which convert the electrical input to the mechanical energy. Here we will see a detailed article related to the starting methods of three phase induction motor. Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. The rotor of three phase induction motor consists of a cylindrical laminated core with parallel slots that can carry conductors.
System is also known as three phase three wire system 3phase 3 wire and it is the most preferred system for ac power transmission while for distribution, star connection is generally used. The three phase induction motors are simple in construction, rugged, low cost and easy to maintain. Such high currents may pose serious problems for the motor and the electrical system when large motors are started. To measure the inrush current when the motor starts.
This article concentrates only on a three phase induction motor and its protection. It is made up of a number of stampings, which are slotted to receive the windings fig. How a single phase motor is similar to 3 phase motor. This system protects the 3 phase ac motor from single phasing and overheating. A single phase induction motor is very similar to a 3 phase squirrel cage induction motor. This application note also covers the basics of induction motors and different types of induction motors. It has i a squirrelcage rotor identical to a 3 phase motor ii a single phase winding on the stator. Methods of starting three phase induction motors as we know, once a supply is connected to a three phase induction motor a rotating magnetic field will be set up in the stator, this will link and cut the rotor bars which in turn will induce rotor currents and create a rotor field which will interact with the stator field and produce rotation. The torquespeed characteristics of the three phase induction motors for varying supply voltage and also for the fan load are shown below. Ansoft rmxprt application note a threephase induction motor problem. These equations can be solved for r2, x1, and x2 as follows. The stator is built up of highgrade alloy steel laminations to reduce eddy current losses.
Several additional components are necessary to operate the single phase motor. By varying the supplying voltage, the speed can be controlled. Find the starting current of 10 hp, three phase 220 v a class motor. A 3 phase, y connected, 460 volt line to line, 25 horsepower, 60 hz, 8 pole induction motor has the following constants, in ohms per phase referred to the stator.
Differentiate between the various types of generating electric power stations. A three phase induction motor problem this application note describes how to set up, solve, and analyze the results of a twopole, three phase induction motor using rmxprt. It is based on freescales 56f800e microcontrollers. To protect the motor from different faults conditions various protections are provided. Analysis of 3 phase induction motor protection using. Lecture 6 three phase induction motors cairo university. The voltage is varied until the torque required by the load is developed, at the desired speed. The stator of an induction motor consists of 3 phase windings, which when connected to a 3 phase supply creates a rotating magnetic field. Like any electric motor, a 3 phase induction motor has a stator and a rotor. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. Analysis of 3 phase induction motor protection using numerical relay dr.
Stator voltage control of an induction motor circuit globe. To obtain the load performance characteristics of a three phase squirrelcage induction motor. An electrical motor is a device that has brought about one of the biggest advancements in the fields of engineering and technology ever since the invention. Some singlephase induction motors are also called squirrel cage motors because of the rotors similarity. There are two basic reasons for the use of single phase motors rather than 3 phase motors. Pdf maximum torque control of 3phase induction motor drives. You should also make a dc measurement of stator winding linetoline resistance using a dmm. Three phase induction motor or ac motor is started by itself but we require some starter or other methods for proper starting and controlling induction motor.
A threephase induction motor problem this application note describes how to set up, solve, and analyze the results of a twopole, three phase induction motor using rmxprt. A three phase, 12 pole, salient pole alternator is coupled to a diesel engine running at 500 rpm. In this case, power flows from the mechanical system, to the rotor circuit, then across the air gap to the stator circuit and external electrical system. This troubleshooting guide can also be applied to other types of three phase induction motors. List and describe the more commonly used equipment in an electric substation. Jul 17, 2016 due to single phasing the induction motor performance severely effected. It has three main parts, outer frame, stator core and a stator winding. Synchronous motors are special types of motors used in constant speed applications, whereas most of the motors used in the industrial applications are of induction type. In this application note, we will generate a third pwm in software, using a general purpose timer and an io pin resource that are readily available on the picmicro microcontroller. Nov 27, 2019 thus from the working principle of three phase induction motor, it may be observed that the rotor speed should not reach the synchronous speed produced by the stator. Applications of three phase induction motors of size varying from half a kilowatt to thousands of kilowatts are numerous. This project is based on the study of three phase induction motor and its faults and other is study of numerical relay.
Form noload test i 0 is known and f 0 is found out as taking all quantities on per phase values. Two digital multimeters and fluke power quality meter with banana cables from the. A 3phase induction motor has two main parts i stator and ii rotor. Load tests on a three phase induction motor and measurement of the inrush current objectives. Single phase induction motors questions and answers. Third international conference on advances in control and optimization of dynamical systems march 15, 2014. To draw circle diagram for a three phase induction motor. Refer back to this diagram as the operational requirements of the singlephase motor are discussed. It supplies an induction motor ich has a full load speed of 144wh 0 rpm. Record all nameplate information for the induction motor. Here we are giving you only overview on 3 phases induction motor. The three phase induction motor is the easiest motor of this type to understand so these notes start with that type.
An843, speed control of 3phase induction motor using pic18 mcus. Torque equation of three phase induction motor electrical4u. The model created by rmxprt will then be used as an input for empulse as a basis for performing more detailed analysis and for increasing the accuracy of the performance pre. Previously we shared the book on ac motors which explains all these properties briefly, this post is focused on the induction motor formulas and calculation examples. The aim of this work focused on numerical relay based protection of three phase induction motor. Nov 27, 2019 the three phase induction motor is the most widely used electrical motor. Single phasing is the most common problem found in three phase induction motor. It supplies an induction motor which has a full load speed of 1440 rpm. A 480v, 60 hz, 6pole, threephase, deltaconnected induction motor has the. If the motor doesnt rotate in two phase operation, find the reason for phase loss and eliminate it.
When the 3 phase stator windings are fed by 3 phase supply, a magnetic flux of constant magnitude which is rotating at synchronous speed is set up. You should also make a dc measurement of stator winding linetoline resistance. Single phase motors have only two power source supply lines connected. Compare the rotation of this motor with that in figure 164. The table below gives the commonly encountered problems in 3 phase squirrel cage induction motors, cause of problems and what remedy to apply to bring the motor back to production. This introduces a complex problem in selecting the proper overload protective devices.
Threephase induction motor protection systems and its. Concept of rotating magnetic field, operating principle, construction, classification and types single phase, three phase, squirrelcage, slipring, doublecage types. Before troubleshooting the 3 phase induction motor, we must have to know about the 3 phase induction motor, star delta starter and its connection diagram. Assuming that the stator resistance r1 is measured at dc and that phase power. Induction motors despite the fact that the three phase motor has more phases than the single phase motor, the single phase motor is a much more complex machine. Difference is that transformer is an alternating flux machine while induction motor is rotating flux machine. Kanpur, india design of a three phase squirrel cage induction motor for electric propulsion system ravi prakash,mohammad junaidakhtar, r. One single phase wattmeter plus miscellaneous apparatus as needed. The very first thing that you should do before starting any type of maintenance on a motor is a visual inspection, a lot of times the trouble can be found just by looking, because if the problem is that bad then it should be very obvious by observation. Phasor diagram of induction motor on noload and loaded conditions, visualization of a three phase induction. Unit 16 electric motors washington state university. The most common type of ac motor being used throughout the work today is the induction motor. Search wegthreephaseinductionmotorsmasterline50019089. The difference in speed between rotor, the synchronous speed and the rotating.
Introduction this application note describes the design of a 3 phase ac induction motor drive with volts per hertz control in closedloop vhz cl. Ac induction motors are also the most common motors used in main powered home appliances. Electrical machines tutorial gate ee krash problem. The stator carries a 3 phase winding called stator winding while the rotor carries a shortcircuited winding called rotor winding only the stator winding is fed from the 3 phase supply. Parida department of electrical engineering national institute of technology, silchar,assam, india email. A 3 phase induction motor uses current delivered in three phases in a sequence into the coils of a stator to create a rotating magnetic field. This strange behavior of single phase induction motor can be explained on the basis of doublefield revolving theory. The main body of the induction motor comprises of two major parts as shows in figure 1. The rotor is separated from the stator by a small airgap which ranges from 0. Construction of three phase induction motor electrical4u. They run at a constant speed from noload to the full load. Search wegthree phase induction motorsmasterline50019089brochureenglish.
Pdf maximum torque control mtc is a new method applied for control of induction motor drives. Design of a three phase squirrel cage induction motor for. 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. For this example, refer to the motor equivalent circuit and calculations described above.
Three phase induction motors draw six or more times rated current when started at rated voltage. Nov 04, 2012 the rotor bars in squirrelcage induction motorsare not straight, but have some skew to reducenoise and harmonics. In section i, different protection of an induction motor and detection of the problems. Starting method for induction motors a 3 phase induction motor is theoretically self starting. A 2pole, 3phase induction motor delivers 37 hp at the shaft at a speed of 2850 rpm on. A 3 phase induction motor can be used for different applications with various speed and load requirements. The single phase induction motor is more subtle and less efficient.
An induction motor also known as an asynchronous motor is a commonly used ac electric motor. In a dc machine, the stator winding is excited by dccurrent and hence the field produced by thiswinding is time invariant in nature. The motor draws more current from remaining two supply lines. Feb 22, 2014 why 3 phase why not 1ph, 4ph, 6ph, 12ph why 3 phase transmission pisquare academy duration.
This induces an electric field in a coil or squirrel cage to drive a rotor. The magnetic field in the air gap from the voltage applied to the stator. Three phase induction motor 3 phase induction motor pdf three phase induction motor diagram single phase induction motor pdf free download speed control of three phase induction motor with universal controller three phase induction motors 3 phase induction mltor the wound rotor induction motor speed control of induction motor induction motor problems and solutions pdf 3 phase motor. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. A threephase induction motor problem enginuity systems. The torque produced by three phase induction motor depends upon the following three factors.
All the three phases are rectified, filtered and regulated and given to operational amplifier where. The stator of an induction motor is, in principle, the same as that of a synchronous motor or generator. Starting of 3 phase induction motors, high starting. One way to reduce the starting current is to start the motor at reduced voltage. Rotating flux is only possible when 3 phase voltage or poly phase which is 120 degree apart in time is applied to a three phase winding or poly phase winding 120 degree apart in space. Maintenance and troubleshooting three phase induction motor. When any of the phases is out, then this system recognizes it and immediately turns off the motor, which is powered by the mains. Jan 11, 2018 such properties include a number of poles, speed, frequency, slip, starting current and rated horsepower. The protective logic are developed in matlab simulink software version 16a. How an induction motor works by equations and physics. The conductors are heavy copper or aluminum bars fitted in each slot and shortcircuited by the end rings. Find the percentage slip and number of poles of the induction motor.
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