Mar 29, 2019 check that the windings are not open or blown. The brushless dc motor, actually an ac motor, is replacing the conventional brushed dc motor in many applications. Design strategy for a 3phase variable frequency drive vfd. 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. Aug 30, 2018 ac motors are fairly basic devices that consist of one or more run windings and one or more start windings. Its operation is based on the principle that when a current carrying conductor is placed in a. 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. Custom motor test systems for ac motors, dc motors, aerospace motors, automotive motors, appliance motors, power tool motors, dentalsurgical motors and pump motors. Mod01 lec39 lecture39testing of dc series motors 40. Noload and blocked rotor test on an induction machine aim. Traction motors in diesel locomotives ee publishers.
May 19, 2008 lecture series on industrial automation and control by prof. If the stator could only develop another current, slightly out of phase from the original current, a revolving field could be assimilated. Check for burnt, damage to body or cooling fan or shaft. 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. This chapter will describe the most common types found on army watercraft. To some, motor speed control is somewhat of a mystical science, a science that causes motors and machines to sometimes operate in unexpected ways. Principle of operation of dc machines, types of dc generators. Nptel provides elearning through online web and video courses various streams. Introduction to ac motors ac motors electronics textbook. Lecture series on industrial automation and control by prof.
The rotor terminals are connected to three slip rings which turn with the. 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. Basic electrical engineering pdf notes bee pdf notes. Ac fundamentals impedance power factor power series. Dc motors although ac motors are used in most of the cases, dc motors have many applications and used for multipurpose applications. Mod01 lec39 lecture39 testing of dc series motors 40.
Electrical machines i online course video lectures by iit. Ac motors are fairly basic devices that consist of one or more run windings and one or more start windings. 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. How to test three phase ac motors learning electrical. Servo motor repair load testing servo motor drive testing. 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. And, the stepper motor, a digital version of the motor, is driven by alternating current square waves, again, generated by solidstate circuitry. Motor current signature analysis mcsa is a proven and accepted method for determining the condition of a motors current carrying components. 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. 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. Basic electrical engineering pdf free download bee notes pdf. Singlephase ac motors are the most common motors built. Losses and torque equation, losses and efficiency calculation in d. Over 30 years ago, ac drives were considered new technology.
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. The figure above shows the family tree of the ac motors described in this chapter. This paper describes the design processes for a 3phase variable frequency drive vfd as broken up into two stages. 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. Basic electrical technology is the most common subject and heart core subject to electrical engineers. Electrical machines i video course electrical engineering nptel. A successful salesman for general electrics motor division once remarked to one of your instructors that, when asked by a customer how a motor. Hence swinburnes test cannot be be conducted on a dc series motor.
Since there is such a wide variety of these motors, it is impossible to describe all of them. The rotor is propelled by a rotating magnetic field realised through 3phase ac supply to the stator winding. 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. 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. They are found everywhere from a small workshop to a large manufacturing industry. Gradually apply three phase voltage across motor stator terminals via the autotransformer d. 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.
Motor and converter performance parameters, 1phase full and semi converter fed dc shunt and dc series motor, mathematical. 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. Different types of electric motors and their applications. A synchronous motor will generate a sinusoidal back emf if the stator magnetic field has a sinusoidal distribution. Electrical engineering electrical machines i nptel.
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. Dc motor principle a machine that converts dc power into mechanical energy is known as dc motor. If there is no voltage or reduced voltage, work back upstream. Principle of operation of dc motors, types of dc motors. Noload and blocked rotor test on an induction machine. It is true that single phase motors are less efficient substitute for 3.
Nptel syllabus electrical machines i video course course outline synchronous machines. At the end of each lesson a set of problem is provided to test. 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. Applications of threephase induction motors of size varying from half a kilowatt to thousands of kilowatts are numerous. A wound rotor, has a 3phase winding similar to the stator winding. Note down the machine ratings and calculate rated current of the machine noload test. An alternating current or voltage is the one which changes periodically both in cycle magnitude and direction. Mukhopadhyay, department of electrical engineering, iit kharagpur. Output frequency and voltage is controlled electronically by controlling the width of the pulses of voltage to the motor. Overview of applications of voltage source converter, motor drives, active frontend converters, reactive compensators, active power filters 3. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. The rotor will constantly be turning to align its magnetic field with that of the stator field.
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. Disconnect any mechanical load connected to the induction motor. Electrical engineering special electromechanical systems nptel. Ac induction motors how ac motors work explain that stuff. The types of ac motors mainly include synchronous, asynchronous, induction motor. The basic idea of an electric motor is to generate two magnetic fields. Constructional features of three phase transformers three phase. Be careful it can hurt to tangle with a threephase motor. Ac motor, main drive controller assembly, and driveoperator interface 210211.
The rotor is propelled by a rotating magnetic field realised through 3phase ac. 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. An ac motor is an electric motor driven by an alternating current ac. Noload and blocked rotor test on an induction machine aim theory. 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. The 3phase set of currents, each of equal magnitude and with a phase. The output of the motor drive is 3phase pulse width modulation pwm ranging in possible operation frequencies from 0hz to khz. Pulse width modulated pwm drives rockwell automation. Without the use of a threephase alternating current, an artificial phase displacement must be established.
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. Our life would be unthinkable without the use of electrical energy. This is the problem encountered by singlephase induction motors. Methods of starting, energy relations during starting and braking, transients in dc and ac drives. The most common type of ac motor being used throughout the work today is the induction motor. Jul 01, 2015 if the motor is completely unresponsive, no ac humming or false starts, take a reading at the motor terminals.
The stator in the electric motor generates the field current which rotates in a stable speed based on the ac frequency. An induction motor also known as an asynchronous motor is a commonly used ac electric motor. If a company wanted to have reliable production, it should stick with known, proven. The ac electric motor used in a vfd system is usually a threephase induction motor. Explain how this motor can be operated as either a synchronous motor or a plain induction motor. Alternating current motors or ac motors are built on the principle that nikola tesla discovered in the late 19th century. 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. Debaprasad kastha, department of electrical engineering, iit kharagpur. Applications of voltage source converters 2 lectures.
The working of the synchronous motor mainly depends on the 3phase supply. Basic electrical technology nptel online videos, courses. And on the other hand, when designed to have a high impedance, the motor has an increased amount of torque in a lowspeed range. The rotor of an induction motor can be a squirrel cage rotor or wound. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. 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. Nptel, online courses and certification, learn for free. 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. The growing utilization of the latter is a decisive prerequisite for the. Hopkinsons test was performed on two similar dc shunt machines and the following results are obtained. Characteristics of induction motors nidec corporation. Describe how a squirrel cage motor is built, and classify it as either an induction motor or a synchronous motor. In this type of drive, a diode bridge rectifier provides the intermediate dc circuit voltage. Electrical engineering basic electrical technology nptel.