PWM BASED BIDIRECTIONAL SPEED CONTROL OF DC MOTOR

PWM BASED BIDIRECTIONAL SPEED CONTROL OF DC MOTOR

AIM OF THE PROJECT

In this project we are going to control the dc motor direction and speed using the single potentiometer by the method of pulse width modulation.

This method is effective, SCR phase angle approach and eliminates the need of reversing switch. The four-quadrant chopper is constructed using MOSFET. The four-quadrant chopper can be used for forward, reversing and braking of the motor

ABOUT THE PROJECT

The speed of the DC motor is varied by varying armature voltage. The variable DC voltage is obtained from chopper. The field voltage is maintained constant. The drive consists of a time delay section

ADVANTGES OF THE DIGITAL CONTROL SYSTEM

§  Realiability and outstanding performance

§  Not affected by component aging

§  Stable performance with respect to temperature change, other affecting situations

POWERFUL FEATURES OF THE PROJECT

§  The DC motor can directly run from AC mains, without any additional starter and rectifier

§  Forward, Reverse and Braking of the Motor

TERMS  - DEFINITION

Voltage

A measure of electrical potential, A measure of the pressure under which electricity flows

High Voltage

Voltage in a power line higher than the volts used

Low Voltage

An electromotive force rated 24 volts nominal or less, supplied from a transformer, converter, or battery

SCR

Silicon Controlled Rectifier: A means of controlling a DC motor's rotation speed

MOSFET

MOSFET (metal-oxide semiconductor field-effect transistor, pronounced MAWS-feht) is a special type of field-effect transistor (FET) that works by electronically varying the width of a channel along which charge carriers (electrons or holes) flow.

The wider the channel, the better the device conducts. The charge carriers enter the channel at the source, and exit via the drain. The width of the channel is controlled by the voltage on an electrode called the gate, which is located physically between the source and the drain and is insulated from the channel by an extremely thin layer of metal oxide

PWM

Pulse Width Modulation. An acronym which describes a switch-mode control technique used in amplifiers and drivers to control motor voltage and current. This control technique is in contrast to linear control and offers the advantages of greatly improved efficiency

RECTIFIER

This is an electrical component in the alternator that contains sets of diodes which are used to change the alternator output from alternating current (AC) to direct current (DC).

DC MOTOR

DC Motor is an electric motor converts electrical energy into mechanical motion. The reverse task that of converting mechanical motion into electrical energy is accomplished by a generator or dynamo. In many cases the two devices differ only in their application and minor construction details

DC motor speed generally depends on a combination of the voltage and current flowing in the motor coils and the motor load or braking torque.

The speed of the motor is proportional to the voltage, and the torque is proportional to the current. The speed is typically controlled by altering the voltage or current flow by using taps in the motor windings or by having a variable voltage supply

Electrical energy or electromagnetic energy is a form of energy present in any electric field or magnetic field, or in any volume containing electromagnetic radiation

The SI unit of electrical energy is the joule, while the unit used by electrical utility companies is the watt-hour (W·h) or the kilowatt-hour (kW·h)

Electrical energy is related to the position of an electric charge in an electric field. The electrical energy of a charge Q situated at the electric potential V equals to the product QV. If V is a potential difference, the same expression gives the energy transformed when the charge moves through the potential difference

DC motor - when the coil is powered, a magnetic field is generated around the armature.

The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation. The armature continues to rotate.

When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats