The Design of DC Motor Driver for Solar Tracking Applications
Abstract - Solar trackers rely on a direct-current (DC) motor driver circuit to control the movement of the solar panel. However, conventional DC motor drivers used in solar tracking system do not provide any options for speed and torque control. Hence, the fixed speed of the DC motor leads to either too fast or too slow tracking movement. Usually, the output torque is set to the maximum. If the load (solar panels’ weight) is small, the maximum torque is not fully utilized and therefore energy is wasted. So, a fully adjustable DC motor driver for solar tracking system shows great potential in commercialization because highly energy efficient DC motor driver circuit can improves the total efficiency of the solar tracker. Fewer solar panels are needed when they are attached to high efficiency solar tracking system, which will be reflected to lower system cost. Therefore, this enhanced motor driver will bring significant impact to the solar energy industry. The proposed DC motor driver is fully adjustable in term of speed and torque. The speed and torque of the motor is directly proportional to the output voltage and output current of the proposed DC motor driver, respectively. Adaptive controlling of the output voltage and current are possible by installing algorithm in the microcontroller of the DC motor driver and it can be reprogrammed according to the requirement. The speed control makes the solar tracking system to track the Sun more accurately and the torque control saves energy.
converter is used to step down the voltage in order to reduce the turning speed of solar panel .
Fig.1. Block diagram of motor driver
Solar tracking system is used to track the position of sun in order to get the maximum energy by aligned the solar panel perpendicular to the incidence sunlight [1, 2, 3, 12, 13]. Solar panels need to move along with the direction of sunlight during the tracking process. A DC motor driver is needed to control the directions as well as the turning speed of the solar panel. The maximum torque of the DC motor decides the total amount of solar panels can be mounted on the tracking system. The common limitation of the DC motor driver is the speed is fixed and the default torque is set to maximum. Logically, it is not preferable to set the motor in high turning speed since Sun tracking is a slow process. While setting the motor to operate at maximum torque causes the system to consume the highest amount of power constantly, regardless of the amount of load attached. It will bring significant impact on the efficiency of the system, since the energy consumed by the system is generated by the solar panel itself. Research has been done that DC-DC buck
However, the system reported has single speed only without torque control. System proposed by V. Gupta managed to control the torque by changing the duty cycle of Pulse Width Modulation (PWM) signal that feed into the low-side switching elements of the H-bridge circuit . The proposed DC motor driver shows that it is possible to make both speed and torque adjustable. It brings great advantage to the solar tracking system as the tracking speed can be optimized according to the tracking condition. Moreover, power consumption of the tracking system can be reduced greatly since the DC motor driver supplies the amount of torque just sufficient to move solar panels attached. An addition current limiting circuit has been added in the motor driver in order to limit the maximum amount of current that can flow through the DC motor to avoid motor stall. Fig. 1 shows the block diagram of the proposed DC motor driver. II. CIRCUIT DESIGN AND DESCRIPTION
A. Characteristic of DC motor
The characteristic of a DC motor is govern by the equation (1): (1) E A = V A- I AR A Where VA is the applied voltage across the DC motor, IA is the armature current, RA is the armature resistance and EA...
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