should be remembered that motor generator set always runs in the same direction. Speed Control of Series Motors: 1. Flux Control Method: Variations in the flux. This Article describes about Different Speed Control Methods in a DC Motor - Shunt and Series methods, Voltage Control & Resistance. Figure Equivalent circuit of a series connected dc motor. In a series dc dc motor has a sharply drooping torque-speed characteristic. . dc motors can also be controlled by the insertion of a series resistor into the motor circuit, but this.
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Abstract: In this paper will be studying about the various speed control methods of a DC series motor. The aim of this this paper is to describe the principle of. chapter, we shall discuss the various methods of-speed control of d.c. motors. . The speed control of d.c. series motors can be obtained by (i) flux control. PDF | Speed of a dc series motor can be controlled using diverter in the field circuit of motor. This paper derives an equation which shows the.
Ward Leonard System. Multiple Voltage Control: The arrangement of this system is as required in the figure shown below. So in this method, the speed can be increased by reducing flux, it puts a method to reducing flux with this method, it puts a method to maximum speed as weakening of flux beyond the limits will adversely affect the commutator. Speed control of a DC motor is either done manually by the operator or by means of an automatic control device.
This method is done by inserting the variable resistance Rc in series with the armature. Due to the voltage back in the controller resistance the back EMF is decreased. Since N is directly proportional to the Eb. Multiple Voltage Control: In this method, the shunt field is connected to a fixed exciting voltage, and the armature is supplied with different voltages. So the Voltage across armature is changed with the help of a suitable switchgear devises.
Armature speed is approximately proportional to the voltage across the armature. Ward-Leonard System: This Ward —leonard system is used where very sensitive speed control of the motor is required e.
The arrangement of this system is as required in the figure shown below. M1 may be any AC motor or DC motor with constant speed. G is the generator directly coupled to M1.
In this method the output from the generator G is fed to the armature of the motor M2 whose speed is to be controlled. The generator output voltage can be connected to the motor M2 and it can be varied from zero to its maximum value, and hence the armature voltage of the motor M2 is varied very smoothly.
Hence very smooth speed control of motor can be obtained by this method. Field Diverter: A Rheostart is connected parallel to the series field as shown in fig a. Hence flux can be decreased to desired amount and speed N can be increased. Armature Diverter: For a given constant load torque, if armature current is reduced, then flux must increase. In this method, field coil is tapped dividing the number of turns. In this method flux is reduced and speed is increased by decreasing the number of the turns of the series field winding.
The switch S can be short circuit any part of the field winding, thus decreasing the flux and raising the speed N with full turns of coil. Paralleling Field Coils: This method gives speed above normal and the method is used in electric drives in which speed should rise sharply as soon as load is decreased.
This is another method of increasing the speed by reducing the flux and it is done by lowering number of turns of field winding through which current flows.
In this method a number of tapping from field winding are brought outside. This method is employed in electric traction. The classification of speed control methods for a DC shunt motor are similar to those of a DC series motor. These two methods are:. In armature resistance control a variable resistance is added to the armature circuit. Field is directly connected across the supply so flux is not changed due to variation of series resistance.
This is applied for DC shunt motor.
This method is used in printing press, cranes, hoists where speeds lower than rated is used for a short period only. This method of speed control needs a variable source of voltage separated from the source supplying the field current.
This method avoids disadvantages of poor speed regulation and low efficiency of armature-resistance control methods. The basic adjustable armature voltage control method of speed d control is accomplished by means of an adjustable voltage generator is called Ward Leonard System. This method involves using a motor-generator M-G set.
This method is best suited for steel rolling mills, paper machines, elevators, mine hoists, etc. This method is known as Ward Leonard System. In this method, speed variation is accomplished by means of a variable resistance inserted in series with the shunt field.
An increase in controlling resistances reduces the field current with a reduction in flux and an increase in speed. This method of speed control is independent of load on the motor. Power wasted in controlling resistance is very less as field current is a small value. This method of speed control is also used in DC compound motor. Static Ward Leonard drives are being used these days because of the drawbacks of the classical method.
Rotating M-G sets are replaced by solid state converters to control DC motor speed. The converters used are choppers in case of DC supply or controlled rectifiers in case of AC supply.