Introduction
When the input quantity (such as voltage, current, temperature, etc.) reaches a specified value, the output circuit to be controlled by the conductive or open electrical appliances. Can be divided into electrical quantity (such as current, voltage, frequency, power, etc.) relay and non-electrical quantity (such as temperature, pressure, speed, etc.) relay two categories. It has the advantages of fast action, stable work, long service life, small size and so on. Widely used in electric power protection, automation, motion, remote control, measurement and communication devices.
1, the working principle and characteristics of electromagnetic relays
Electromagnetic relays are generally composed of iron core, coil, armature, contact reeds and so on. As long as the coil ends plus a certain voltage, the coil will flow through a certain current, resulting in an electromagnetic effect, the armature will be attracted in the electromagnetic force under the action of overcoming the return of the spring tension suction to the iron core, which drives the armature's moving contacts and static contacts (normally open contacts) suction. When the coil is powered off, the electromagnetic suction also disappears, the armature will return to its original position under the reaction force of the spring, so that the movable contact and the original static contact (normally closed contact) release. This suction, release, so as to achieve the purpose of conduction in the circuit, cut off. For the relay "normally open, normally closed" contacts, can be distinguished in this way: the relay coil is not energized in the disconnected state of the static contacts, known as "normally open contacts"; in the on state of the static contacts known as "normally closed contacts "
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2, the working principle and characteristics of the thermal reed relay
Thermal reed relay is a new type of thermal switch using heat-sensitive magnetic materials to detect and control the temperature. It consists of a temperature-sensitive magnetic ring, a constant magnetic ring, a reed switch, a thermally conductive mounting piece, a plastic backing and some other accessories. The thermal reed relay does not use coil excitation, but the magnetic force generated by the constant magnetic ring to drive the switch action. The ability of the constant magnetic ring to provide magnetic force to the reed switch is determined by the temperature control characteristics of the temperature-sensitive magnetic ring.
3, solid-state relay (SSR) principle of operation and characteristics
Solid-state relay is a two-terminal for the input, the other two terminals for the output of the four-terminal device, the middle of the use of isolation devices to achieve the input and output of the electrical isolation. According to the type of load power supply, solid state relay can be divided into AC type and DC type. According to the switch type can be divided into normally open and normally closed type. According to the isolation type can be divided into hybrid, transformer isolation type and photoelectric isolation type, photoelectric isolation type for the most.
4, reed relay
Reed relay is a coil to generate a magnetic field will be reed actuated relay, for a coil sensing device. Therefore, the characteristics of reed relay, small size, light weight, fast response time, short beat time and other characteristics. When a piece of ferromagnetic metal or other magnetically conductive material is in close proximity to a reed relay, it will act to open or close a circuit. Composed of permanent magnets and reed switches. Permanent magnet, reed switch fixed in a non-conductive and non-magnetic bracket. The axis of the north and south poles of the permanent magnet should coincide or almost coincide with the axis of the reed switch. Adjust the distance between the permanent magnet and the reed switch from far to near, and fix the position of the magnet when the reed switch just happens to be actuated (for a normally open reed switch, it becomes closed; for a normally closed reed switch, it becomes disconnected). At this time, when there is a whole piece of magnetic material, such as iron plate close to the magnet and the reed switch at the same time, the reed switch will once again be actuated, restored to the state when there is no magnetic field; when the iron plate leaves, the reed switch will be actuated in the opposite direction. Reed relays have a sturdy structure, sealed contacts and high durability, and can be used as position limiting switches for mechanical equipment, or for detecting whether an iron door, window, etc. is in a specified position.
5, optical relay
Optical relay for AC/DC and semiconductor relays, refers to the light-emitting device and the integration of light-emitting devices. Input side and output side of the electrical insulation, but the signal can be transmitted through the optical signal. It is characterized by semi-permanent life, small current drive signal, high impedance insulation voltage, ultra-compact, optical transmission, no contact ...etc.. It is mainly used in measuring equipment, communication equipment, security equipment, medical equipment, etc..