Dc motors although ac motors are used in most of the cases, dc motors have many applications and used for multipurpose applications. Ac induction motors how ac motors work explain that stuff. Custom motor test systems for ac motors, dc motors, aerospace motors, automotive motors, appliance motors, power tool motors, dentalsurgical motors and pump motors. The growing utilization of the latter is a decisive prerequisite for the. Disconnect any mechanical load connected to the induction motor. Dc motor principle a machine that converts dc power into mechanical energy is known as dc motor. Servo motor repair load testing servo motor drive testing. When a motor is designed in such a way that impedance of the aluminum conductor of the rotor is reduced, its efficiency is increased in a highspeed range. Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. It is true that single phase motors are less efficient substitute for 3. Nptel, online courses and certification, learn for free.
Basic electrical technology is the most common subject and heart core subject to electrical engineers. The brushless dc motor, actually an ac motor, is replacing the conventional brushed dc motor in many applications. Aug 30, 2018 ac motors are fairly basic devices that consist of one or more run windings and one or more start windings. The output of the motor drive is 3phase pulse width modulation pwm ranging in possible operation frequencies from 0hz to khz. At the end of each lesson a set of problem is provided to test. Constructional features of three phase transformers three phase.
They are found everywhere from a small workshop to a large manufacturing industry. If the stator could only develop another current, slightly out of phase from the original current, a revolving field could be assimilated. Mar 29, 2019 check that the windings are not open or blown. 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. Hopkinsons test was performed on two similar dc shunt machines and the following results are obtained. Applications of voltage source converters 2 lectures. Electrical engineering electrical machines i nptel. This is the problem encountered by singlephase induction motors. The induction motor is made up of the stator, or stationary windings, and the rotor. Note down the machine ratings and calculate rated current of the machine noload test. An induction motor also known as an asynchronous motor is a commonly used ac electric motor. An everyday ac induction motor with its case and rotor removed, showing the copper windings of the coils that make up the stator the static, nonmoving part of the motor. Basic electrical engineering pdf notes bee pdf notes. At servotech we are dedicated to providing the highest quality servo motor repair and refurbishment services, and have designed our servo repair process to ensure we return your.
Noload and blocked rotor test on an induction machine. Applications of threephase induction motors of size varying from half a kilowatt to thousands of kilowatts are numerous. The rotor of an induction motor can be a squirrel cage rotor or wound. The rotor is propelled by a rotating magnetic field realised through 3phase ac supply to the stator winding. The figure above shows the family tree of the ac motors described in this chapter. An alternating current or voltage is the one which changes periodically both in cycle magnitude and direction. Traction motors in diesel locomotives ee publishers. The rotor terminals are connected to three slip rings which turn with the. In this type of drive, a diode bridge rectifier provides the intermediate dc circuit voltage. The ac electric motor used in a vfd system is usually a threephase induction motor. Electrical engineering basic electrical technology nptel. Mukhopadhyay, department of electrical engineering, iit kharagpur.
The types of ac motors mainly include synchronous, asynchronous, induction motor. Noload and blocked rotor test on an induction machine aim theory. This chapter will describe the most common types found on army watercraft. Ac motors are fairly basic devices that consist of one or more run windings and one or more start windings. In particular, if a coil rotates in the presence of a magnetic field, the induced emf varies sinusoidally with time and leads to an alternating current ac, and provides a source of ac. The rotor is propelled by a rotating magnetic field realised through 3phase ac. A wound rotor, has a 3phase winding similar to the stator winding. Overview of applications of voltage source converter, motor drives, active frontend converters, reactive compensators, active power filters 3. Describe how a squirrel cage motor is built, and classify it as either an induction motor or a synchronous motor.
A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit traction motors are used in electrically powered rail vehicles electric multiple units and other electric vehicles including electric milk floats, elevators, roller coasters, conveyors, and trolleybuses, as well as vehicles. Principle of operation of dc motors, types of dc motors. The basic idea of an electric motor is to generate two magnetic fields. Mod01 lec40 lecture40characteristics of compound dc series motors freevideolectures aim to help millions of students across the world acquire knowledge, gain good grades, get jobs. Electrical machines i iitkgp course view notes l37tbet ee nptel from electrical ee212 at international institute of information technology. Without the use of a threephase alternating current, an artificial phase displacement must be established. Explain how this motor can be operated as either a synchronous motor or a plain induction motor. Many simple across the line singlephase and 3phase motors used in household appliances and industry respectively can be checked simply by changing the range of the ohm meter to the lowest offered r x 1, zeroing the meter again, and measuring the resistance between the leads of the motor. Motor testing methods based on iec 6003421 p ll determined from residual loss 8. Gradually apply three phase voltage across motor stator terminals via the autotransformer d. Let us discuss in brief, the ac fundamentals necessary to analyse the networks consisting of various alternating current and voltage sources, resistances and inductive, capacitive reactances. In general, the induction motor is cheaper and easier to maintain compared to other alternatives.
The most common type of ac motor being used throughout the work today is the induction motor. A synchronous motor will generate a sinusoidal back emf if the stator magnetic field has a sinusoidal distribution. Nptel provides elearning through online web and video courses various streams. A successful salesman for general electrics motor division once remarked to one of your instructors that, when asked by a customer how a motor. Losses and torque equation, losses and efficiency calculation in d. And, the stepper motor, a digital version of the motor, is driven by alternating current square waves, again, generated by solidstate circuitry. A variablefrequency drive is a device used in a drive system consisting of the following three main subsystems. An ac motor is an electric motor driven by an alternating current ac. Basic electrical technology nptel online videos, courses. Methods of starting, energy relations during starting and braking, transients in dc and ac drives. The working of the synchronous motor mainly depends on the 3phase supply. Design strategy for a 3phase variable frequency drive vfd.
In the intermediate dc circuit, the dc voltage is filtered in a lc lowpass filter. They only have two moving parts, the rotor and the start switch, which means that they are pretty easy to test and fix when you notice something is going wrong with the device. Basic electrical engineering pdf free download bee notes pdf. And on the other hand, when designed to have a high impedance, the motor has an increased amount of torque in a lowspeed range. An ac motor of this type may be part of a pump or fan or connected to some other form of mechanical equipment such as a winder, conveyor, or mixer. Nptel syllabus electrical machines i video course course outline synchronous machines. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. Take readings at accessible points including disconnect s, the motor controller, any fuses or junction boxes, and so on, back to the overcurrent device output at the. Our life would be unthinkable without the use of electrical energy. Electrical machines i video course electrical engineering nptel. Testing of induction motor december 30, 2018 february 24, 2012 by electrical4u demand of energy is growing day by day and along with it cost of energy rising abruptly, so now it is necessary that the health of large motors which. Hence swinburnes test cannot be be conducted on a dc series motor. Testing can be conducted without interrupting the normal operation of the motor, and in fact should be performed when the motor is under a minimum of 70% load. If a motor is driven by sine waves of current synchronous with the motor back emf, it is classified as a synchronous ac motor, regardless of whether the drive waveforms are generated by electronic means.
The ac motor commonly consists of two basic parts, an outside stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft producing a second rotating magnetic field. They only have two moving parts, the rotor and the start switch, which means that they are pretty easy to test and fix when you. May 19, 2008 lecture series on industrial automation and control by prof. If a company wanted to have reliable production, it should stick with known, proven. Ac motor, main drive controller assembly, and driveoperator interface 210211.
Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. Mod01 lec39 lecture39 testing of dc series motors 40. Jul 01, 2015 if the motor is completely unresponsive, no ac humming or false starts, take a reading at the motor terminals. A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit traction motors are used in electrically powered rail vehicles electric multiple units and other electric vehicles including electric milk floats, elevators, roller coasters, conveyors, and trolleybuses, as well as vehicles with. Motor and converter performance parameters, 1phase full and semi converter fed dc shunt and dc series motor, mathematical. Over 30 years ago, ac drives were considered new technology. If there is no voltage or reduced voltage, work back upstream. Electrical engineering special electromechanical systems nptel. Permanent magnet synchronous motor pmsm the pmsm is a 3phase ac synchronous motor with the usual squirrel cage or induction construction replaced by magnets fixed in the rotor. The principle of an ac motor is that electric current is applied to electromagnets, creating a rotating magnetic field to convert electrical energy to rotation mechanical energy.
Debaprasad kastha, department of electrical engineering, iit kharagpur. How to test three phase ac motors learning electrical. Alternating current motors or ac motors are built on the principle that nikola tesla discovered in the late 19th century. Singlephase ac motors are the most common motors built. Since there is such a wide variety of these motors, it is impossible to describe all of them.
This paper describes the design processes for a 3phase variable frequency drive vfd as broken up into two stages. Its operation is based on the principle that when a current carrying conductor is placed in a. Motor current signature analysis mcsa is a proven and accepted method for determining the condition of a motors current carrying components. Lecture series on industrial automation and control by prof. The rotor will constantly be turning to align its magnetic field with that of the stator field. Dec 30, 2018 testing of induction motor december 30, 2018 february 24, 2012 by electrical4u demand of energy is growing day by day and along with it cost of energy rising abruptly, so now it is necessary that the health of large motors which consumes maximum power should be taken care off. Characteristics of induction motors nidec corporation. Principle of operation of dc machines, types of dc generators. The stator in the electric motor generates the field current which rotates in a stable speed based on the ac frequency. The 3phase set of currents, each of equal magnitude and with a phase. Output frequency and voltage is controlled electronically by controlling the width of the pulses of voltage to the motor. Be careful it can hurt to tangle with a threephase motor. Without going into the mathematical details, the wave shape of the induced emf can be explained by the fact that the rate of change of flux. Different types of electric motors and their applications.
Pulse width modulated pwm drives rockwell automation. Ac fundamentals impedance power factor power series. Servo motor repair load testing we service well over a hundred servo manufacturers, with rush services available for rapid spindle, ac and dc servo motor repair. Electrical machines i online course video lectures by iit. Noload and blocked rotor test on an induction machine aim. Introduction to ac motors ac motors electronics textbook. Check for burnt, damage to body or cooling fan or shaft. These coils are designed to produce a rotating magnetic field, which turns the rotor the moving part of the motor in the space between them. Mod01 lec39 lecture39testing of dc series motors 40.
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