Electromagnetic relay generally consists of iron core, coil, armature and contact reed. As long as a certain voltage is applied to both ends of the coil, a certain current will flow in the coil, thus generating an electromagnetic effect. Under the attraction of electromagnetic force, the armature overcomes the pulling force of the return spring and attracts the iron core, thus driving the moving contact of the armature to attract the stationary contact (normally open contact). When the coil is powered off, the electromagnetic attraction disappears, and the armature will return to its original position under the reaction of the spring, so that the moving contact and the original static contact (normally closed contact) are disengaged. In this way, it is attracted and released, so as to achieve the purpose of making and breaking the circuit. For the normally open contacts and normally closed contacts of relays, we can distinguish them as follows: the static contacts that are disconnected when the relay coil is not energized are called "normally open contacts"; Static contacts in the on state are called "normally closed contacts". Relays generally have two circuits, namely, a low-voltage control circuit and a high-voltage working circuit.
Working principle and characteristics of solid state relay (SSR)
Solid-state relay [1] is a four-terminal device, in which two terminals are input terminals, the other two terminals are output terminals, and an isolation device is adopted in the middle to realize the electrical isolation of input and output.
According to the type of load power supply, solid state relays can be divided into AC type and DC type. 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 photoelectric isolation type, with photoelectric isolation type being the most.
Working principle and characteristics of hot reed relay
Thermal reed relay is a new type of thermal switch which uses thermomagnetic materials to detect and control temperature. It consists of a temperature-sensing magnetic ring, a constant magnetic ring, a reed switch, a heat-conducting mounting piece, a plastic substrate and other accessories. The hot spring relay does not need coil excitation, but the magnetic force generated by the constant magnetic ring drives the switch to act. Whether the constant magnetic ring can provide magnetic force to the reed switch is determined by the temperature control characteristics of the temperature sensing magnetic ring.
Working principle and characteristics of magnetic reed relay
Magnetic reed relay is a kind of coil induction device, which uses the magnetic field generated by the coil to drive the magnetic reed tube. Therefore, the magnetic reed relay has the characteristics of small volume, light weight, fast response speed and short jump time.
When the whole piece of ferromagnetic metal or other magnetic conductive substance approaches it, it will open or close the circuit. Consists of a permanent magnet and a reed switch. The permanent magnet and the reed switch are fixed on a bracket that is neither magnetic nor magnetic. Take the connecting line between the north and south poles of the permanent magnet as the axis, which should coincide or basically coincide with the axis of the reed switch. Adjust the distance between the permanent magnet and the reed switch from far to near, and when the reed switch just moves (for the normally open reed switch, it becomes closed; For normally closed reed switch, close), fix the position of the magnet. At this time, when a whole piece of magnetic conductive material, such as iron plate, approaches the magnet and the reed switch at the same time, the reed switch will act again and return to the state without magnetic field; When the iron plate leaves, the reed switch moves in the opposite direction. Magnetic reed relay has firm structure, sealed contacts and durability. It can be used as a limit switch for mechanical equipment, and can also be used to detect whether iron doors and windows are in the designated position.
Working principle and characteristics of optical relay
Optical relay is a kind of semiconductor relay with AC /DC, which refers to the integration of light emitting device and light receiving device. The input side and the output side are electrically insulated, but signals can be transmitted by optical signals.
It has the characteristics of semi-permanent life, low current driving signal, high impedance insulation and voltage resistance, ultra-miniaturization, optical transmission and non-contact.
Mainly used in measuring equipment, communication equipment, safety equipment, medical equipment, etc.
Working principle of time relay
Time relay is a kind of control electrical appliance which uses electromagnetic principle or mechanical principle to realize time delay control. There are many kinds of it, including air damping, electric and electronic.
Air damping time relay is often used in AC circuit, which uses the principle of air throttling through small holes to obtain delayed action. It consists of electromagnetic system, delay mechanism and contact.
Time relays are divided into two types: power-on delay type and power-off delay type.
The air damping time relay has a large delay range (0.4~60s, 0.4 ~ 180s).
Its structure is simple, but its accuracy is low.
When the coil is energized (the voltage specification is ac380v, ac220v or dc220v, dc24v, etc.). ), the armature and the support plate are attracted by the iron core, and move down instantly, so that the instantaneous action contact is connected or disconnected. However, the piston rod and the lever cannot fall at the same time as the armature, because the upper end of the piston rod is connected with the rubber film in the air chamber. When the piston rod starts to move downward under the action of the release spring, the rubber film sinks downward, and the air in the upper air chamber becomes thinner, so that the piston rod is damped and slowly descends. After a certain period of time, when the piston rod descends to a certain position, the lever pushes the delay contact to act, so that the moving contact is disconnected and closed. The time from the energization of the coil to the completion of the delay contact action is the delay time of the relay. The length of the delay time can be changed by adjusting the size of the air inlet hole of the air chamber with screws.
After the attraction coil is cut off, the relay is reset under the action of the reset spring. Air is quickly exhausted through the air outlet.