PWM Controlled Fan Load using DC motor
PWM CONTROLLED FAN LOAD USING DC MOTOR
Aim: To model a fan type load in Simulink and to control its speed by using the PWM method
Theory:
The use of pulse width modulation to control a small motor has the advantage in that the power loss in the switching transistor is small because the transistor is either fully “ON” or fully “OFF”. As a result, the switching transistor has a much-reduced power dissipation giving it a linear type of control which results in better speed stability.
Pulse width modulation is a great method of controlling the amount of power delivered to a load without dissipating any wasted power.
Mathematical formula:
Load Torque proportional to square of speed (fan type)
T = K * w ^ 2
Model Explanation:
From simulation model we can see that the controlled voltage source input is given by pulse generator. After that this signal goes to H-bridge. This H bridge is used for change the direction of rotation of motor. It is basically driver circuit which drive the dc motor. Except for the PWM port, all of the H-Bridge block's input ports are connected to ground in this model. When the motor is on, the H-Bridge block connects the motor terminals to the power supply.
Simulation Time: 50Sec
Simulink model of the PWM Controlled Fan load using DC motor
Pulse Generator Input
Fan Load
Scope Output
Torque-Speed characteristics of FAN
Description/Calculation:
PWM is provided by control PWM voltage Block through it is pass to H- bridge converter which is used to change the direction of rotation of motor, it is basically a driver circuit
For fan load we do not have any block to represent the fan so we are actually representing it by a subsystem with the use of square law, that represented as fan load. We can control the fan by using this particular circuit
We can represent the speed variation and torque variation with respect to time in scope block but to see variation in torque and speed we have to see in XY-graph Block.
Here, the DC Motor block has speed of 2500 rpm and no-load speed of 4000 rpm when run from a 12V DC supply.
Observations: This model shows how to use the Controlled PWM Voltage and H-Bridge blocks to control a motor
Conclusion: A PWM controlled DC motor using an H bridge circuit was modelled in Simulink and results were analysed. The load torque characteristics of a fan is obtained.
Reference: https://skill-lync.com/student-projects/pwm-controlled-fan-load-using-dc-motor