International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 02 | Feb -2017
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e-ISSN: 2395 -0056 p-ISSN: 2395-0072
Study On Speed Control of DC MOTOR Using Thyristor Ankita Ringe1, Ragini Sonbarse2, Prof. Apurva Bhalerao3 1Ankita
Ringe, Department of Electrical (E&P), DES’SCOET, Maharashtra, India Sonbarse, Department of Electrical (E&P), DES’SCOET, Maharashtra, India 3Prof. Apurva Bhalerao, Department of Electrical (E&P), DES’SCOET, Maharashtra, India ---------------------------------------------------------------------***--------------------------------------------------------------------1.1 Introduction to Thyristor Abstract - The DC motor is an main part of equipment in 2Ragini
many industrial applications requiring variable speed and load characteristics due to its easy controllability. There are two different types of control loops, current controller and speed controller. This DC motors are widely used in the industries because of its versatile characteristics which have contributed in the extensive use of the DC motor in the industry. The DC motor can control by various method which are as field control, armature voltage control, armature resistance control. The Thyristor based DC drive with the analog and digital feedback control schemes are used for the speed control technique of DC motor. This drive also providing the functions like Start, Stop, Forward braking, reverse braking, increased and decreased speed of motor. This paper deal with the speed control of separately excited DC motor control in the better performance manner.
Key Words: DC motor, speed control, Thyristor, etc… 1.INTRODUCTION An electrical drives consists of electrical motors, power controllable and energy transmitting shaft. This electrical drives are widely used in the industry because of its low cost, less complex control structure and wide range of speed and torque. In modern electrical drive system power electronics converter are used as power as power controller. Electrical drives are mainly of two types: DC drives and AC drives. They are different from each other in this way that the power supply in DC drives in provided by DC motor and power supply in AC drives provided by AC motor. Standard motors are classified as either constant speed or adjustable speed motors. Adjustable speed motors may be operated over a wide speed range by controlling armature voltage and field excitation. The speed below the base speed can be controlled by armature voltage control method and field control method is used for the above base speed. In past, many researchers worked on various converter topologies of DC motor control for different industrial applications [5], but all of them are thyristor based. For simulation of various topologies MATLAB with its tool boxes like Simulink and Sim Power System are used [3].
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A thyristor is a solid-state semiconductor device with four of alternating N and P-type material. It acts as a bistable switch, conducting when gate receives a current trigger and continuing to conduct while the voltage acreoss the device is not received. A three-lead thyristor is designed to control the large current of its two leads by combining that current with the smaller current of its other lead, known as its control lead. Some sources defines silicon-controlled rectifier and thyristor as synonymous. Other sources define thyristor as a large set of device with at least four layers of alternating N and P-types material. The first thyristor device was released commercially in 1956. Because thyristor can control a relatively large amount of power and voltage will a small device, they find wide application in control of electric power, rating from light dimmers and electric motor speed control to highvoltage direct current poer transmission. A thyristor unsuitable as an analog amplifier, but useful as a switch. A silicon controlled rectifier or semiconductor-controlled rectifier is a four-layer solid-state current controlling device.
2. MATHEMATICAL MODELING OF DC MOTOR To analyse the torque speed characteristics, power factor and total harmonics distortion, the dynamics and steady state model of separately excited DC motor is required. Figure shows the schematic representation of the model of a separately excited DC motor, in which E a is the terminal voltage applied to the motor, Ra and La are the resistance and inductance of the armature circuits respectively. Rf and Lf are the resistance and inductance of the field circuit respectively, Eb is generated back emf and Tm is the electromagnetic torque developed by the motor. The related DC motor parameter are mentioned in appendix A. Due to the interaction of the field flux with current in armature conductors, the torque is produced which is given by Eq.(1) Tm=ktՓ ia
(1)
Here Kt is a constant depending on motor winding and geometry and Փ is the flux per torque produced. When armature rotates, the flux linking the armature winding will vary with time and therefore according to Faraday’s law, an emf will be include across the winding. This generated emf, knows an the emf, depends on speed of rotation as well as on the flux produced by the field and given by Eq. (2) ISO 9001:2008 Certified Journal
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