The characteristics and laws of power relays 01

As can be seen from the various examples mentioned above, any power relay, regardless of its operating principle, structural type, and application situation, is a certain signal (electrical or non-electrical) input according to the outside world. An appliance that controls the "on" and "off" of current in a circuit. This is its commonality. This commonality shows that in order to complete its specific mission, any power relay should have a corresponding induction mechanism that can respond to a certain input signal from the outside world, and an executive function that realizes "on and off" control of the controlled circuit. Corresponding actuator. Since the action of the power relay's actuator requires a certain physical quantity, and the external input signal has two types of electricity and non-electricity, the induction mechanism of the power relay should first have an induction function as follows: Convert the input electricity or non-electricity into a certain specific physical quantity suitable for the action of the actuator. This function is called the conversion function, and the corresponding part is called the conversion mechanism. In addition, the execution of the power relay required by the controlled object, It is only executed under a certain amount of input, not arbitrary execution under an arbitrary input. Therefore, the induction mechanism of the power relay should also have another important induction function: it can compare and judge the size of the input, when When the input quantity reaches a certain value, a signal is given to instruct the execution mechanism to execute. This function is called a comparison function, and the corresponding part is called a comparison mechanism.

In this way, the transformation and comparison can realize the requirement of responding to a certain external input signal, and complete the whole function of induction. For example, the iron core and coil in the electromagnetic power relay can convert the input voltage or current signal into electromagnetic force; the bimetal in the temperature or thermal power relay can convert the input temperature or thermal signal into its internal bending force. These are the performance of the conversion function, and they become the conversion mechanism of the power relay. The return spring in the electromagnetic power relay generates a certain amount of pressure due to the previous compression, so that the contact system can only act when the electromagnetic force is equal to (or slightly greater than) this force; the butterfly bimetal in the temperature power relay , because the butterfly shape is made in advance, the sudden reversal can only occur when the temperature rises to a certain value; between the free end of the straight bimetallic sheet and the contact system in the thermal power relay, there is a certain gap in advance, so that the Only when the heat reaches a certain level can the bimetallic sheet push the contact system. These are the manifestations of the comparative function, and they are a kind of comparative agency. Likewise, in all other  power relays, we can find their corresponding sensing parts. As for the power relay's actuator, that's pretty obvious. The contacts in the contact power relay can produce opening and closing actions. The transistors in the non-contact semiconductor power relay have two states of cut-off and saturation, which can realize the control of the circuit's off and on, which is a manifestation of the executive function. the actuator of the power relay. It can be seen that "induction" and "execution" are indispensable to any power relay. It can even be said that these two parts are must-haves in other switching appliances. Because the execution without induction is arbitrary execution, and the induction without execution is blind induction, neither of which can constitute a complete switching appliance, and of course it cannot complete the specific mission of the switching circuit that it undertakes. Therefore, any power relay or other switching device is the unity of these two interdependent parties.