DC MOTOR SPEED CONTROL USING CHOPPER
Abstract : The Objective of the paper is to control the separately excited dc motor by using the IGBT based chopper. The speed of separately excited dc motor can be control by varying the armature voltage and varying field flux. Thus the speed can be controlled for under rated speed and speed beyond the rated speed, respectively. In this paper, the motor speed under and up to the rated speed can be achieved by varying the Armature voltage. IGBT based chopper Controls the Armature voltage. The IGBT chopper takes signal from controller and Adjustable voltage is given to the armature of dc motor as per the wanted speed. The advantages to employee this technique is that the Speed varies equivalently with armature voltage and varies inversely with field voltage by keeping field and armature voltage persistent respectively. The IGBT employed chopper i.e. power module gives smoother control as compared with the SCR based circuit. By using this system, we can chop the frequency and speed of DC motor can be control.
? The main objective of this paper is the easy implementation of hardware of electronic circuitry based speed control of DC motor. For the required speed the speed controller takes signal represent and to drive a motor at required speed.
? Armature voltage control method is used to control the speed of separately exited dc motor and this armature voltage can be controlled through various ways but we choose chopper circuit for voltage regulation.
? Because the light source (LED) and photodiode are physically kept separated (with 2mm) in the package, isolation opto 2500V can be used.
? Though it is not a main or necessary component but it is useful for precautionary purpose.
? There is a need to control current in motor armature. To solve the above problem we can employ a current controller which will take care of motor rated current limit.
? The development of various solid state switching devices in the thyristor families along with variety of different digital chips in control/firing circuits has made an impact in the area of DC drive.
? Change the polarity of the voltage and motor can spins in other direction, but this idea have some of disadvantages if suddenly reverse the voltage on DC motor during spinning.
? It Cause a current surge that can burn out the speed controller.
• The system is modelled and simulated to study the transient and steady state behaviour.
• Pulse-width modulation is a widely used technique for control of power converters and motors. The hardware model of the proposed system is built in the laboratory and experimentally to examine the system.
• The simulation results and experimental results are found to be in good agreement. In this paper speed control of DC series motor is using a chopper is proposed.
• The system consists of a SEPIC chopper to control the output voltage given to the motor. The SEPIC converter consists of single MOSFET which operates in ON-OFF modes.
? These are also used in trolley cars, marine hoist, forklift trucks and mine haulers. Chopper systems offer smooth control, high efficiency, faster response and regeneration facility. Chopper can be used as a converter to control the speed of separately excited DC motor.
? The speed control can be achieved above or below the rated speed. Controller receives the signal from the chopper firing circuit and then the chopper gives variable voltage to the armature of the motor for achieving desired speed.
? The field windings of the dc motor are used to excite the field flux.
? The rotor torque is produced by interaction of field flux and armature current. The controller used in a closed loop provides a very easy and common technique of keeping motor speed at any desired set-point speed under changing load conditions.
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