1. Field of the Invention
This invention relates to an electrical energy saving device for motors, which comprises a principal circuit system operating with a control circuit system for automatically adjusting the magnitude of the input power of the motor with respect to the different load states of the motor.
2. Related Art
Conventionally, all motor control systems have not been provided with a specially designed triggering device for controlling the conducting condition of the motor. Therefore, when the motor is in an idle running state or the load thereof is light, the input current drawn by the motor is still kept at 50-70% of the full-load current. This mode of operation not only consumes too much energy and reduces the power factor of the system, but also decreases the life span of the motor because of the high temperature suffered by the motor when running at this current level.
Although control elements, such as a SCR or a TRIAC, are used in conventional motor control circuits for triggering the running state of the motor, owing to the fact that the magnitude of the starting current is usually 7-8 times of the zero-load current, the specifications of such control elements must be augmented, which causes a significant increase in the manufacturing costs. On the other hand, a timing device is also used in conventional control circuit as a starting and overload protecting device, but it has to be matched with an electromagnetic switch, which increases substantially the volume of the control device as well as the manufacturing costs. Besides, the timing device, which achieves an overload protection only during the starting period, provides no protection during the running state of the motor. Furthermore, conventional motor control circuit systems cannot be installed at the front end of the power source switch, and are very inconvenient in utilization, replacement and adjustment operations.