Abstract:
Domestic fans are a widely used appliance all around the world. There are several types
of fan controllers available for the speed controlling of the fans. Since the cost is a
dominant factor when the relevant market is concerned, low cost fan controllers are
popular among them even though there are several drawbacks. This thesis discusses
design and implementation of a utility friendly hum less remote control fan controller
unit at an affordable price.
Electronic fan controllers are used due to the compact design and the low cost. It allows
speed reduction through out the range. Most of the available fan controllers use voltage
controlling while keeping the frequency constant to control the speed. The mostly
available dimmer circuits consist of Triacs as the switching device. Wave form is
chopped by an electronic circuit to reduce the line voltage. This generates low order
harmonics which affect the utility power while making irritating noise especially at low
speeds.
The proposed system designed with a power circuit with power IGBTs as the switching
device which uses microprocessor based control system as the signal generator. The
algorithm is developed under Harmonic Elimination PWM scheme which switches the
power circuit in firing angles which avoids low order harmonics at the predefined speed
levels.
The designed system fire the power IGBTs at pre defined firing angles at selected speed
levels. It avoids the 3 r d 5t h and 7t h order harmonics below 80% of the line voltage at the
operation while avoiding 3 r d and 5t h above 80% of the line voltage. This reduces the
irritating noise and the speed pertabations at the low speed while ensuring a linier speed
control action with utility friendly operation.
