Working principle and characteristics of electromagnetic relay
Working principle: when the electromagnet is electrified, the armature is sucked down to make D and e contact, and the working circuit is closed. When the electromagnet loses its magnetism, the spring pulls up the holding iron and cuts off the working circuit.
1. Working principle and characteristics of electromagnetic relay
Electromagnetic relay is generally composed of electromagnet, armature, spring and contact. Its working circuit is composed of low-voltage control circuit and high-voltage working circuit. Electromagnetic relay can also realize remote control and automatic control. As long as a certain voltage is applied to both ends of the coil, a certain current will flow through the coil, resulting in electromagnetic effect. The armature will overcome the pulling force of the return spring and attract to the iron core under the attraction of electromagnetic force, thus driving the moving contact and the static contact (normally open contact) of the armature to pull in. When the coil is powered off, the electromagnetic suction will disappear, and the armature will return to the original position in the spring reaction force, so that the moving contact and the original static contact (normally closed contact) will be released. In this way, the circuit can be switched on and off. For the “normally open and normally closed” contacts of relay, it can be distinguished as follows: when the relay coil is not energized, the static contact in the off state is called “normally open contact”; the static contact in the on state is called “normally closed contact”.
2. Working principle and characteristics of thermal reed relay
Thermal dry spring relay is a new type of thermal switch which uses thermal magnetic material to detect and control temperature. It consists of a temperature sensing magnetic ring, a constant magnetic ring, a dry reed, a heat conducting mounting plate, a plastic substrate and some other accessories. The thermal dry spring relay does not need coil excitation, but the magnetic force generated by the constant magnetic ring drives the switch action. Whether the constant magnetic ring can provide magnetic force to the reed is determined by the temperature control characteristics of the temperature sensing magnetic ring.
3. Solid state relay（ SSR:Solid-state relay ）Working principle and characteristics of
Solid state relay (SSR) is a kind of four terminal device with two terminals as input and the other two terminals as output.
Solid state relay 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 photoelectric isolation type, and the photoelectric isolation type is the most.
Application of electromagnetic relay
Anti alarm: K is a contact switch, B is a funnel-shaped bamboo cylinder, in which there is a float A. when the water level rises beyond the warning line, the float a rises, so that the control circuit is connected, and the electromagnet sucks the armature, so the alarm indicator circuit is connected, and the light is on for alarm.
Automatic temperature alarm: when the temperature rises to a certain value, the water silver surface of mercury thermometer rises to the metal wire, and mercury is the conductor. When the temperature drops, the mercury surface leaves the wire, the electromagnet circuit is disconnected, the spring piece returns to its original state, the electric bell circuit is disconnected, and the electric bell no longer sounds.