3 phase ac motor theory pdf

Threephase induction motors are also called asynchronous motors. Construction and working of 3 phase induction motor on ship. A mean value of r and z should be taken from the blocked rotor readings and used to calculate i. Module 8 ac reactive components this module describes inductance and capacitance and their effects on ac circuits. The most common type of ac motor being used throughout the work today is the induction motor.

This is a great advantage, giving 3 phase machines 48% greater capacity than. A three phase induction motor is a type of ac induction motors which operates on three phase supply as compared to the single phase induction motor where single phase supply is needed to operate it. Characteristically, linear induction motors have a finite primary or secondary length, which generates endeffects, whereas a conventional induction motor is arranged. Driving the three phase stepper motor is achieved by implementing and controlling the duty cycle of pwm signals of the mcu. In addition, there is an energysaving drive highefficiency magnetic motor ipm for further energy saving. Theory and analysis of three phase induction motor using. The motor driven by the inverter is a mainly three phase squirrelcage motor, and the motor driven by the vector inverter is three phase type motor with encoder which detects a position and speed. There are two basic reasons for the use of single phase motors rather than 3 phase motors. Characteristics of a three phase and single phase induction motor.

One component defines the magnetic flux of the motor, the other the torque. The stator of three phase induction motor is made up of numbers of slots to construct a 3 phase winding circuit which we connect with 3 phase ac. In 7 and e dynamic induction motor models have been developed where the squirrel cage and the 3 phase stator winding are represented by. Induction motors objective the aim of this chapter is to gather knowledge about the following topics of induction motors. This results in a mechanical jerk and high electrical stress on the windings of the motor. In this chapter, the development of the model of a threephase induction motor. Uvw are the ends of the phases and c the common most likely. A three phase induction motor consists of three phase windings as it remains stationary due to which it is called the stator. The stator carries a 3phase winding called stator winding while the rotor carries a. For this example, refer to the motor equivalent circuit and calculations described above.

For reason of economy, most houses, offices and also rural areas are supplied with single phase a. The premise for motor operation is that if you can create a rotating magnetic field in the stator of the motor, it. In this chapter, the development of the model of a threephase induction motor is examined starting with how the induction motor operates. These threephase motors consist of a stator and a rotor and between which no electrical connection exists. A 1phase induction motor is similar to a 3phase squirrel cage induction motor. The stator of an induction motor consists of 3 phase windings, which when connected to a 3 phase supply creates a rotating magnetic field. Driving threephase stepper motor with bldc motor driver. Basic construction of 3phase ac induction motors you. The strength of the magnetic field changes, as the current flow in the coils of wire around the stator poles change.

The transformer has a range of output voltage taps that can be used to set the start voltage. They are found everywhere from a small workshop to a large manufacturing industry. The three phase ac induction motor is a rotating electric machine that is designed to operate on a three phase supply. Langsdorf, theory of alternating current machinery, 2nd. A linear induction motor lim is an alternating current ac, asynchronous linear motor that works by the same general principles as other induction motors but is typically designed to directly produce motion in a straight line. Explain what slip speed is for an ac induction motor, and why there must be such as thing as slip in order for an induction motor to generate torque. Vf control of 3phase induction motors using pic16f7x7. The three phases of the motor are driven by the three outputs of the drv83, as figure 3 shows. These 3 phase motor is supplied with 3 threephase ac supply and is widely used in ships for heavier loads. The modulated signal controls the on and off time of the power mosfets in the halfbridges, which in turn controls the output current and voltage supplied to the windings of the three phase stepper motor. It is based on motorolas dsp56f805 dedicated motor control device. Ac induction motors, which contain a cage, are very popular in variable speed drives. Still a popular choice for a new 400 hz military and commercial aerospace applications. The primary core grey has grooves, and the windings are laid into them on top of each other.

Vf control a discussion of induction motor control theory is beyond the scope of this document. Start the motor by ensuring the shaft is at no load condition. There are two major components of an ac induction motor. Easy to predict motor performance for a three phase motor windings, notoriously difficult for a single phase designs. In the three phase induction motor, the rotating magnetic field is produced by supplying currents to a set of stationary windings, with the help of a three phase ac power supply.

The induction motor should start smoothly and gradually catch up the speed for a safer operation. The three phase windings are displaced from each other by 120 0. Construction, types and principle of operation of 3 phase induction motors. This application note explains how these microcontrollers can be used for 3 phase ac induction motor control. Most 9lead motors can be operated on 208v, but the running current increases by about 10%, and the. This module presents power calculations for singlephase and threephase ac. Jul 11, 2006 if you write out the 3 phase currents as explicit functions of time i maxcos. The currentcarrying windings produce the magnetic field or flux due to which the interaction of three magnetic fields or fluxes produced, resultant magnetic field or. The power is applied steadily as in dc circuits not in pulses as in single phase ac circuits. The pic16f7x7 series of microcontrollers have three onchip hardware pwm modules, making them suitable for 3 phase motor control applications. This 3 phase motor is also called as an asynchronous motor. Three phase ac motor theory motors have been described as a transformer with a rotating secondary. The theory used in the work was collected by studying literature on how.

To explain the design of a squirrelcage motor, a three phase, twopole motor will be illustrated. Ac induction motor vector control, driven by etpu on mpc5500. Other motors that are included are 1 phase induction motors, permanent synchronous motors and synchronous reluctance motors. However you would have seen that distribution lines usually have only 4 wires. This portable document format \ pdf \ file contains bookmarks, thumbnails, and hyperlinks to help you navigate through the document. The advantages of three phase ac induction motor are listed below. The difference between the speed of the rotating magnetic field fixed by line power frequency and the speed of. It has been shown that in this speed mode, seriesconnected induction motor scim has superior characteristics compared to those of conventional induction.

The real purpose of this question is to get students to recognize the main handicap of a single phase ac motor, and to understand what is required to overcome that limitation. Generators, dc motors, ac theory, ac power, ac generators, voltage. The associated ac generator is producing just one flow of electrical current whose direction and intensity varies as indicated by the single solid line on the graph. Basically, a dc voltage is applied to the stator windings of a 3 phase im. Induction motors are most commonly used as they offer better performance than other ac motors. There are many types of ac motors, but this course focuses on three phase ac induction motors, the most common type of motor used in industrial applications. I may assume it is a 12 pole 3 phase motor each phase has 4 coils in crosspattern. An electrical motor is an electromechanical device that converts electrical energy into mechanical energy. For starting, either use autotransformer or starter. Which of these altered motor connections will result in the motor reversing direction. On the theory of 3phase squirrelcage induction motors. Assuming that i a, i b, i c are the instantaneous currents in the. From time 3 to time 6, current is flowing in the negative. Basic construction of 3phase ac induction motors you should.

Schematic representation of a sinusoidal voltage of magnitude e applied on a circuit with a resistive load r. The derivation of the dynamic equations, describing the motor is explained. Suad ibrahim shahl 26 equivalent circuit model analysis example a 480v, 60 hz, 6pole, three phase, deltaconnected induction motor has the following parameters. This application note discusses the basics of an ac induction motor. Pump steel mill, hoist drives, household applications are few applications of induction machines. Dc motors, ac theory, ac power, ac generators, voltage regulators, ac. The three phase induction motor during the initial starting condition draws up much higher current than its capacity and the motor instantly reaches the full speed. 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.

The schematics shows the resultant current i in phase with the voltage v. A three phase system has alternating current and voltage waves, with each successive phase occurring 120 degrees after the previous phase that alternate 60 times per second for a 60 hz system. The ac induction motor is the most used electrical motor in industrial applications worldwide. Just as the current in the field windings rise and fall 120 electrical degrees apart, so does the resulting magnetic field on the pole face. Motors, generators, and transformers are similar in that their basic principle of operation involves induction. Single phase induction motor, theory of operation double revolving field. In the case of three phase ac alternating current operation, the most widely used motor is a 3 phase induction motor, as this type of motor does not require an additional starting device. Pdf theory and analysis of threephase seriesconnected. Like any electric motor, a 3phase induction motor has a stator and a rotor. The singlephase induction motor is not selfstarting. The challenge question essentially asks students what happens to a three phase motor that is suddenly forced to operate as a single phase motor due to a line failure. The basic principle of operation is described by faradays law.

Schematic diagram for noload test on three phase induction motor. An aluminium plate above not shown serves as secondary and will move relative to the primary if a 3 phase ac is applied. 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. It also shows the phasor representation of the voltage and current. Ac motors are used worldwide in many applications to transform electrical energy into mechanical energy. This document includes the basic motor theory, system design concept, hardware implementation, and software design, including the pc master software. Starting method for induction motors a 3 phase induction motor is theoretically self starting. An887, ac induction motor fundamentals microchip technology. Ac induction motors are also the most common motors used in main powered home appliances. Hence, the induction machine is a doublyexcited machine in the same sense as the synchronous and dc machines. Vector control, also called fieldoriented control foc, is a variablefrequency drive vfd control method in which the stator currents of a three phase ac or brushless dc electric motor are identified as two orthogonal components that can be visualized with a vector.

This module presents power calculations for single phase and three phase ac circuits and includes the power triangle concept. The handbook includes information on alternating current ac and direct current dc theory, circuits, motors, and generators. Pdf the popularity of 3 phase induction motors on board ships is because of their simple, robust construction, and high reliability factor in the. Volume 3 of 4 module 7 basic ac theory this module describes the basic concepts of alternating current ac electrical circuits and discusses the associated terminology. Applications of three phase induction motors of size varying from half a kilowatt to thousands of kilowatts are numerous. Motor start theory autotransformers thermal overload 3 phase auto transformer b start contactor a start contactor run contactor 3 m the autotransformer starter employs an autotransformer to reduce the voltage during the start period. Single phase induction motor double revolving field theory the three phase induction motor starting torque inversely depends on the slip this implies that a small positive slip 0. This current space vector depicts the three phase sinusoidal system. In addition to providing basic information about ac motors. Theory about three phase induction motor basics electricity. The windings are supplied by a balanced three phase ac power supply. From time 0 to time 3, current is flowing in the conductor in the positive direction. Ac induction motor vector control, driven by etpu on mpc5500, rev. Explain what will happen to the magnetized rotor when 3 phase ac power is applied to the stationary electromagnet coils.

April 11, 20 3 of 10 the rotor receives its excitation by induction from the armature field. The three phase winding is usually connected in star or delta fashion. Apply some 12v at one phase say u and ground to pg. Double revolving field theory and principle of operation. One single phase wattmeter plus miscellaneous apparatus as needed. To 3 phase motor power source m1 also, explain the operation of this motor control circuit. You should also make a dc measurement of stator winding linetoline resistance. Pdf three phase ac motor theory fajr alfurqon academia. This theory makes use of the idea that an alternating uniaxial quantity can be. The lines of a three phase power system may be connected to the terminals of a three phase motor in several di. The principle of operation of this motor is based on the production of a rotating.

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. Record all nameplate information for the induction motor. The principle of operation of three phase induction motors is based on the. This reference design describes the design of a 3 phase ac induction vector control drive with position encoder coupled to the motor shaft.