When the input quantity (such as voltage, current, temperature, etc.) reaches the specified value, the controlled output circuit is turned on or off an electrical appliance. It can be divided into two categories: electrical (such as current, voltage, frequency, power, etc.) relays and non-electrical (such as temperature, pressure, speed, etc.) relays. It has the advantages of fast action, stable work, long service life and small size. It is widely used in power protection, automation, motion, remote control, measurement and communication devices.
Relay is an electronic control device, it has a control system (also known as an input loop) and a controlled system (also known as an output loop), usually used in automatic control circuits, it is actually a kind of "automatic switch" to control a larger current with a smaller current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.
The working principle and characteristics of electromagnetic relays
Electromagnetic relays are generally composed of iron cores, coils, armatures, contact reeds, etc. As long as a certain voltage is added to both ends of the coil, a certain current will flow through the coil, resulting in an electromagnetic effect, and the armature will overcome the tensile force of the return spring under the action of electromagnetic force attraction and attract to the core, thereby driving the dynamic contact of the armature to engage with the static contact (normally open contact). When the coil is de-energized, the electromagnetic suction force disappears, and the armature returns to its original position under the reaction force of the spring, so that the moving contact engages with the original static contact (normally closed contact). In this way, it is engaged and released, so as to achieve the purpose of conduction and cutting in the circuit. For the "normally open, normally closed" contacts of relays, they can be distinguished as follows: the static contacts that are in the open state when the relay coil is not energized are called "normally open contacts"; Static contacts that are turned on are called "normally closed contacts".
The working principle and characteristics of thermal reed relays
Thermal reed relay is a new type of thermal switch that uses thermal magnetic materials to detect and control temperature. It is composed of a temperature sensing magnetic ring, a constant magnetic ring, a reed switch, a thermally conductive mounting sheet, a plastic substrate and some other accessories. Thermal reed relays do not use coil excitation, but are driven by the magnetic force generated by the constant magnetic ring. Whether the constant magnetic ring can provide magnetic force to the reed switch is determined by the temperature control characteristics of the thermosensitive magnetic ring.
The working principle and characteristics of Solid State Relays (SSRs).
The solid-state relay is a four-terminal device with two terminals as the input terminal and the other two terminals as the output terminal, and the intermediate isolation device is used to realize the electrical isolation of the input and output.
Solid state relays can be divided into AC type and DC type according to the type of load power supply. According to the switch type, it can be divided into normally open type and normally closed type. According to the isolation type, it can be divided into hybrid type, transformer isolation type and optoelectronic isolation type, with the optoelectronic isolation type being the most.
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1. Working process:
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