Power electronics and drives nptel pdf squarespace. The graph shows the torquespeed characteristics of a shunt dc motor. Previously, you saw that a dc motor is made up basically of a fixed magnet stator and a rotating magnet rotor. Focus is on topics of interest to the mechatronics engineer shunt connected dc motor permanentmagnet dc motor a simplified method of analysis is used. In mechanical system, speed varies with number of task so speed control is necessary to do mechanical work in a proper way. Assuming the motor is a perfect motor no wind resistance or friction in the armature, then in a no load situation the only power drawn by the motor is the power required to energise. In a shunt motor, the field and armature windings are connected in parallel.
Shunt motor is a special type of dc motor which runs at. C shunt, ii separately excited and iii series motor widely used are given at the beginning. Shunt motor or selfexcited generator the shunt connection is in which the field is connected in parallel, or shunt with the armature. Construction and principle of operation of the shunt dc motor. To know how to estimate and predict efficiency of a d. Shunt motors have field winding connected in parallel with the armature winding. When a permanent magnet is positioned around a loop of wire that is hooked up to a d. The torquearmature current characteristics example 4. If the motor needs to operate at full load, determine i input current, ii speed. Simplified dc motor with an electromagnet as stator. To limit i a, a resistance is inserted in series with r a then removed after the development of e c a t a r v i. Dc motors may be termed as shunt, series, compound or separately excited.
Equivalent circuit of compound excited dc motor differential compound torque. Assignment a starter circuit has to be designed for a 24hp, 250v and 80a dc shunt motor, such that the maximum starting current is limited to 250 percent of its rated armature current and as soon as the current falls to rated value, the sections of starting resistors are to be cut out. The objective of the algorithm is to control the vector components of the stator magnetic field i. Field volts and amps shunt fields are typically wound for 150 vdc or 300 vdc. This document is highly rated by students and has been viewed 921 times. Characteristics and application of shunt, series and compound motors. Shunt dc motors find very wide use in constant speed requirements since the drop in the speed from its noload speed is relatively small. Jan 25, 2019 operating characteristics of separately excited dc motor 1 both in shunt wound dc motor and separately excited dc motor field is supplied from constant voltage so that the field current is constant. A good material for the poles of a pmdc motor should have the apposite of the above. Assuming continuous conduction, calculate firing angle in degree for rated motor torque and 750 rpm. The characteristics of a shunt motor reveal that it is an approximately constant speed motor. Our sample motor has a winding that can be connected to either 150 vdc or 300 vdc. To limit i a, a resistance is inserted in series with r a.
For a dc motor, the efficiency is the electrical output power divided by the mechanical input power, or for a dc generator, the efficiency is the electrical output power divided by the mechanical input power, or note that the efficiency of a dc machine will vary. Jul 10, 2020 before knowing about the differences between dc series and shunt motors, let us start to know what a dc motor is. Separately excited dc motor shunt dc motor permanent magnet dc motor. Many dc motors use an electromagnet for the stator, as illustrated in figure 27.
Speed control of separate excitation dc motors using control recator. Therefore these two motors have similar speed armature current and torque armature current characteristics. Blocks pertinent to the control of the dc motor are modeled using basic blocks found in the simulink library. Mod01 lec30 lecture30characteristics of dc shunt motors. Motor starters 3 point and 4 point starters protective devicescalculation of starter steps for d. Lesson 12 shunt connected dc motors engineering siu. Derive the transfer fb unction of an armature controlled dc motor. Derive the transfer fb unction of an armature controlled dc motor and draw the closed loop block diagram.
It describes principle,procedure to find stray loss in dc shunt motor with mathematical analysis. Draw the circuit model of a shunt motor and label all parts correctly use the shunt motor equations to perform calculations on shunt dc motor operation draw and explain how the shunt motor torque speed. Threephase brushless dc motor field oriented control the field oriented control foc algorithm allows to obtain the maximum performance from a bldc motor. An electric motor that is powered up by direct current is termed as dc motor. Methods of starting, energy relations during starting and braking, transients in dc and ac drives. The open circuit voltage of a dc shunt generator is 127 v. A 440v dc shunt motor draws 40a while supplying the rated load at 1500rpm. A dc series motor operating at 800 rpm draws a line current of 100a from 230v supply.
T0, time for the motor speed to drop to 20 rpm, and. Shunt dc motor the shunt motor is probably the most common dc motor used in industry today. Since they are connected in parallel, the armature and field windings are exposed to the same supply voltage. A 240 v short shunt com pound dc motor, series resistance 0.
At noload condition, the motor runs at rpm and the armature current takes 6 a. Dc motors plays an important role in energy conversion process. How is the speed of a shunt motor affected by a varying. Equivalent circuit of dc shunt motor a figure shows the equivalent circuit of a dc shunt motor which consists of three first order differential equations and two algebraic equations. Shunt motor gives almost constant speed for over wide range of mechanical load torques. Series field coil shunt field coil armature ra the characteristics. So back emf is a controlling factor of armature current. Speed control techniques for a dc motor are available in two types. For a dc motor, the efficiency is the electrical output power divided by the mechanical input power, or for a dc generator, the efficiency is the electrical output power divided by the mechanical input power, or note that the efficiency of a dc machine will vary with the operating conditions i. Debaprasad kastha, department of electrical engineering, iit kharagpur. However, it is not recommended for variablespeed application. The voltage from the armature is applied directly to the field in the case of a generator, while for motor operation the source voltage is applied to the field and armature. The direction of rotation of a dc shunt motor can be reversed by changing the polarity of either the armature coil or the field coil. How is the speed of a shunt motor affected by a varying load.
The working principle of a dc shunt motor is, whenever a dc motor is turned on, then dc flows throughout stator as well as the rotor. Multiplying both sides of voltage equation 1 by i a, we get the power equation of a dc motor as follow. Find the speed at which the motor operates for a line current of 25a, assuming that the flux at this current is 45% of the original flux at 100a. In a detailed view, when a currentcarrying conductor is positioned in the area of a certain magnetic field, it gains some torque and tends to have a moment. Oct 25, 2020 a dc shunt motor also known as a shunt wound dc motor is a type of selfexcited dc motor where the field windings are shunted to or are connected in parallel to the armature winding of the motor. A 20hp, 250v dc shunt motor has an armature resistance of 0. Jan 05, 2021 dc machines nptel notes edurev is made by best teachers of. The output mechanical power is of shunt dc motor is maximum when the back e. Resistance of the armature circuit including brushes is 0.
Pdf speed and torque control of a dc shunt motor elmer r. Mathematical modeling and dynamic simulation of dc motors. The dc shunt motor is 120vdc with rated speed of 1800 revolutions per minute. Field economizing in many applications it may be necessary to apply voltage to the shunt field during periods when the motor is stationary and. Apparatus type range quantity 1 voltmeter mc 0300v 1 2 ammeter mc 020a 1 3 rheostat 1250.
Dc motors are divided into three classes, designated according to the method of connecting the armature and the field windings as shunt series and compound wound. The armature resistance of a 200 v shunt dc motor is 0. When power for the stator electromagnet is supplied by a separate dc source, either. This motor can be constructed with the basic parts like field windings stator, a commutator and an armature rotor the working principle of a dc shunt motor is, whenever a dc motor is turned on, then dc flows throughout stator as well as the rotor. Figure 1216 shows the electrical diagram of a dc shunt motor connected to a forward and reversing motor starter. In this application the armature coil is usually changed, as was the case with the series motor. Dc motors, generators and energy conversion devices 1 lesson 12 332a. It is a machine which converts electrical energy into mechanical energy. Mathematical modeling and dynamic simulation of dc. Power, voltage and emf equation of a dc motor formulas.
To control the speed of dc shunt motor by armature control method and field control method apparatus requirred. The armature current can be written as tb a a v e i r where r a is armature resistance, p zn e b 60a i armature current is proportional to back emf. A 10 hp, 230v dc shunt motor has an armature resistance of 0. For shunt field dc motor, the field is in parallel to the armature winding. The above relation is known as voltage equation of the dc motor. Mathematical model of direct current shunt motor figure 6. Equivalent circuit parameters are armature resistance ra 110 ohms, field resistance rf 2. Craig 3 introduction the brushed dc motor is not as widely used today as in the past, but it is still being used, especially at the lowpower level. Motor types shunt, series, and compound connections.
Electrical engineering electrical machines i nptel. Dc machine are the electromechanical energy conversion devices which converts either dc. Speed control of dc shunt motor with field and armature. The armature and field coils are connected in parallel in a d. This motor can be constructed with the basic parts like field windings stator, a commutator and an armature rotor.
Mechanical characteristics speed torque characteristics of various types of load and drive motors braking of electrical motorsdc motors. The equations from 6 to 10 are used to build the simulink model of dc shunt motor. When its field magnets are excited and its armature conductors. Components of the shunt motor are the armature, labeled a1 and a 2, and the field, labeled f1 and f2. In this lesson aspects of starting and speed control of d. The coils in the shunt field are composed of many turns of small wire, resulting in low shunt field current and moderate armature current. Lathes, drills, boring mills, shapers, spinning, and weaving machines series motor. When the machine is loaded the terminal voltage becomes 120 v.
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