What are the best ways to control the speed of dc motor. What are the methods for controlling the speed of a dc shunt motor. A simple explanation of how to control the speed of a dc motor. Dc motor speed control and basics dc motor speed control and basics skip navigation. A brushed dc electric motor is an internally commutated electric motor designed to be run from a direct current power source.
On occasion, a field regulator is contained within the field circuit of dc shunt motor for additional speed adjustment. Speed control of dc motor shunt, series, and compound often we want to control the speed of a dc motor on demand. In general the speed of a shunt dc motor is directly proportional to the armature voltage and inversely proportional with the field current, disregarding inherent losses. Speed control of dc motor using pulsewidth modulation. Speed control of dc shunt motor your electrical guide.
I discuss the field resistance methos of speed control of dc shunt machinesthis lecture is a bit longbut it is worth it i have also put a. Lecture 16 dc motor speed control introduction youtube. The fieldof the generator g is also supplied from the exciter e. To study the speed control of a dc shunt motor by the following methods. Gopakumar, centre for electronics design and technology, iisc bangalore. Indeed one of the primary reasons for the strong competitive position of dc motors in modern industrial drives is the wide range of speeds afforded. When a motor operates a center elector motive force e is induced in the armature as a result of conductors rotating and cutting the flux. Shunt wound dc motor or dc shunt motor is a selfexcited dc motor whereas we said before at previous article types of dc motor that it operates on direct current and the field winding is connected in parallel to the armature winding so both windings exposed to the same power supply voltage, and this motor able to maintain at a. Speed control methods of dc motor speed control of shunt motor 1. We discuss speed control and the characteristics of a dc shunt motor. The field current can be changed by changing the rheostat r connected in series with the field. By varying the current supplied to the rotor by varying the current supplied to the stator as the voltage around the rotor and stator is the same, the speed of the motor can be controlled by controlling the current through the stator or rotor. Jul 11, 2019 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.
As resistance increased, the value of the field current will reduce. Electrical machinel dc laboratory manual grietelectrical and. Thus by decreasing the flux, speed can be increased and vice versa. Series wound dc motor construction, principle, speed and torque. Feb 10, 2019 its called speed regulation of a dc motor, which is the capability a dc motor shows to recover the speed under variable load. At present, variable voltage is achieved by scr controlled ac to dc converter unit is used to. So some series resistors connected in series with the motor and switched in and out. The speed characteristic of a shunt motor is different compared with a series motor. In order to change the speed, we have to change flux.
Jul 30, 2017 dc motor speed control and basics dc motor speed control and basics skip navigation. Speedcontrolofdcshuntmotor page 1 experiment no 9 aim. The circuit of a simple speed controller for a mini dc motor, such as that used in tape recorders and toys, is shown in fig. In the armature control method, the speed of the dc motor is directly proportional to the back emf eb and eb v iara. Sep 30, 2017 speed torque characteristic dc shunt motor. To study the methods of controlling the speed of shunt dc motor. The field of the shunt motor is supplied from a constantvoltage exciter e. This is different to speed regulation where the speed is trying to be maintained or regulated against the natural change in speed due to a change in the load on the shaft.
Because of their selfregulating speed capabilities, dc shunt motors are ideal for applications where precise speed control is required. The set up for speed control of dc shunt motor using flux control technique is shown in the figure. This can be achieved by changing the field current. One of the most important features of the dc motor is that their speed can easily be control according to the requirement by using simple methods.
The flux of a dc motor can be changed by changing ish with help of a shunt field rheostat. Speed control of shunt motor by field rheostat starting the principle of starting a shunt motor will be seen from figure 4 which shows the faceplatetype starter, the starting resistance being in between the segments marked 1, 2, 3, etc. Jul 11, 2019 speed control of a dc motor is either done manually by the operator or by means of an automatic control device. This intentional change of drive speed is known as speed control of a dc motor. Keep in mind, however, that they cannot produce high starting torque, so the load at startup must be small. Because of this feature, this motor is used for automotive and industrial purposes where fine precision of the motor speed is required. By means of this method, the motor can be worked at any speed up to its maximum speed. The simple rheostatic method provides a speed torque characteristic dc shunt motor with little hardness and little stability. Speed control of dc motor shunt type aim a to study the speed control of dc motor below the normal range by armature resistance control and to plot speed vs armature voltage, characteristic. Speed control methods of dc shunt motor my tech info. A machine that converts dc electrical power into mechanical power is known as dc motor. The armature of the shunt motor m whose speed is to be controlled is connected directly to a d. Speed control of dc motor shunt, series and compound. One can control the speed of a dc shunt motor in two ways.
It is already explained above that the speed of a dc motor is inversely proportional to the flux per pole. A compound dc motor connects the armature and fields windings in a shunt and a series combination to give it characteristics of both a shunt and a series dc motor. Then the resistance r is increased due to which shunt field current i sh decreases, decreasing the flux produced. K e b o where, kconstant this shows the speed of a dc motor is directly proportional to the back emf and inversely proportional to the flux per pole.
By decreasing the flux, the speed can be increased and vice versa. As a result, the optimize of the control can be realized very difficultly in the speed control. Speed control of dc shunt motor by applied voltage in this method, the field winding of the motor is connected to a constant dc voltage. Armature resistance control and field flux control the dc motor converts the mechanical power into dc electrical power. Variations of speed with armature voltage control at constant field current. Speed control of dc motor using pulse width modulation, 555. Construction and principle of operation of the shunt dc motor.
Speed of a dc motor can be controlled by various ways, like flux control. The relationship given below gives the speed control of dc motor, therefore, the speed of the 3 types of dc motors shunt, series, and compound can be controlled by changing the quantities on the righthand side of the equation above. When the load is extremely low within a shunt motor, then the armature current can also be low. Thus by varying the pulsewidth, we can vary the average voltage across a dc motor and hence its speed. Speed control of dc shunt motor with field and armature rheostat. The voltage applied to the motor may be reversed by backing the field current of generator through controller fc. In the past, wardleonard method is used for voltage control method.
Speed control of dc motors field control shunt motor. Pdf this paper discusses the speed and torque control of a shunt dc motor through matlab simulink simulations. The dc shunt motor is 120vdc with rated speed of 1800 revolutions per minute. A more efficient way to proceed is by using pulse width modulation technique to control the speed of our dc motor. Variation of speed with variation of field current at constant voltage. The speed of a shunt motor can be changed by flux control method. The different methods of speed control in dc shunt motors are explained below, flux control method armature control method voltage control.
The shunt motor runs at a speed defined by the expressions. Dc shunt motor shunt wound dc motor principle, construction. Since they are connected in parallel, the armature and field windings are exposed to the same supply voltage. Speed control methods of dc motor shunt, series motors. The preceding discussion shows that armature voltage variation gives creeping speeds. Which of the following motors is used where the required starting torque is high and speed control is desirable. Therefore speed of the 3 types of dc motors shunt, series and compound can be controlled by changing the. The performance of speed regulation of ac motor can compare with that of dc motor after the foc. This paper discusses the speed and torque control of a shunt dc motor through matlab simulink simulations. Apr 17, 2008 lecture series on power electronics by prof. Speed control of dc shunt motor with field and armature rheostat control 79 2. Series wound dc motor as we said before that this type of dc motor is a selfexcited dc motor which converts electrical power into mechanical power based on electromechanical law, but in this motor, the field winding is connected in series to the armature winding.
In fact, fine speed control is one of the reasons for the strong competitive position of d. What is a dc shunt motor and its advantage and disadvantage. Speed control methods of dc shunt as well as dc series motor are. The speed of dc motors are easily controlled by varying the voltage applied. Speed control of a dc motor is either done manually by the operator or by means of an automatic control device. Speed control of dc shunt motor with field and armature. Dc motor speed control using pwm method circuit explanation. Such a fine speed control is generally not possible with a.
The speed control of dc motors are in general much more adaptable speed drives than ac motors which are associated with a constant speed rotating field. So current through shunt field winding is also at its rated value. As such, the field windings and armature are connected in a parallel combination, and in electrical terminology a parallel combination is known as a shunt. But armature is supplied with different voltages with the help of suitable switch gear as shown in the figure. When supply voltage v and armature resistance ra are kept constant, the speed is directly proportional to armature current ia. Brushed motors were the first commercially important application of electric power to driving mechanical energy, and dc distribution systems were used for more than 100 years to operate motors in commercial and industrial buildings. Apr 08, 2018 the second reason is if we want to use any devices like microcontrollers or any other digital equipment for automating our dc motor speed control, then this method cannot be used. Working principle from the above circuit diagram, we can conclude that if we want to increase the speed of the shunt motor, we will vary the field resistance. Speed control of dc motor the speed of a dc motor is given by i flux control.