Project 1

PWM controlled Fan load Using DC moto

Objective:

TO model a fan type load in simulink and control its speed by using the PWM method

Abstrack:

The primary emphasis of his work is to model a dc motor driven by an input signal that approximate a pulse width modulation signal . These signal are fed to the motor using an H bridge circuit. Furture we focused on the implementation of speed control of a fan at the motor output . We assume that the change of opratiing speed of the fan is through stepwise modulation through a fan regulator

Keyword:

PWM, H bridge , DC motor

Introduction :

This paper present the work for the degine of the fan speed control system using pulse width modulation by establishing a connection between an H bridge circuit andd a DC motor . A fan type load equation has been used to analyes the output result instead of a physiscal model of a fan in simulink . The speed of the fan is varid according to the input voltage using PWM Technique

By changing or modulating the timing of these pulse the speed of the motor can be controlled . A stepwise change in the speed varriation is given and the full load speed is observed . In the model all input port of the H bridge block accept the PWM port are connected to ground . As a result the H brodge block behave as follow

. When the motor is on , the H bridge block connected the motor terminal to the power

. When the motor is off , the H bridge block act as a freewheeling diod to maintain the motor current

Pulse width modulation :

Pulse width modulation or PWM is a technique for getting analog result with digital means . Digital control creates a square wave a signal switch betweeeen on and off . This ON OFF pattern can simulate voltages in between fulll ON and OFF by changing the portion of the time the signal spendd on versus the time that the signal spend the duration of ON time " is callled pulse width . To get varying analog value we change or modulate that pulse width

Model description ;

The DC motor block user manufactuer datasheet parameters which specify the motor as delevering 10W mechenical power at 2500 rpm and no load speed as 4000 rpm when run from a 12V DC supply . H bridge block represent a motor drive . The block can be driven by the controlled PWM voltage block in averaged mode

Conclusion ;

A PWM controlled DC motor using an h bidge circuitb was modelled in simulink and result were analysed . the output plot justified the theory discussed . The load torque charachertics of a fan is obtained . the full speed was observed for a full voltage of 12V from DC motor