Relay working principle and characteristics introduction

Power Directional Relay

Working principle and characteristics

When the input quantity (such as voltage, current, temperature, etc.) reaches the specified value, the controlled output circuit is turned on or off. It can be divided into two categories: electrical quantity (such as current, voltage, frequency, power, etc.) relays and non-electrical quantity (such as temperature, pressure, speed, etc.) relays. It has the advantages of fast action, stable operation, long service life, and small size. It is widely used in power protection, automation, motion, remote control, measurement and communication devices.

Working principle and characteristics of electromagnetic relay

Electromagnetic relays are generally composed of an iron core, a coil, an armature, and a contact spring. As long as a certain voltage is applied to both ends of the coil, a certain current will flow through the coil, thereby generating an electromagnetic effect. The armature will overcome the pulling force of the return spring under the action of the electromagnetic force and be attracted to the iron core, thereby driving the moving contact of the armature to close with the static contact (normally open contact). When the coil is powered off, the electromagnetic attraction will also disappear, and the armature will return to its original position under the reaction force of the spring, so that the moving contact and the original static contact (normally closed contact) are attracted. In this way, the attraction and release achieve the purpose of conduction and disconnection in the circuit. The "normally open and normally closed" contacts of the relay can be distinguished as follows: the static contact in the disconnected state when the relay coil is not powered is called the "normally open contact"; the static contact in the connected state is called the "normally closed contact".

Working Principle and Characteristics of Thermal Reed Relays

The thermal reed relay is a new type of thermal switch that uses thermal magnetic materials to detect and control temperature. It consists of a temperature-sensitive magnetic ring, a constant magnetic ring, a reed switch, a heat-conducting mounting plate, a plastic substrate and some other accessories. The thermal reed relay does not use coil excitation, but the magnetic force generated by the constant magnetic ring drives the switch to operate. Whether the constant magnetic ring can provide magnetic force to the reed switch is determined by the temperature control characteristics of the temperature-sensitive magnetic ring.

Working Principle and Characteristics of Solid State Relays

A solid-state relay is a four-terminal device with two terminals as input terminals and the other two terminals as output terminals. An isolation device is used in the middle to achieve electrical isolation between input and output.

Solid-state relays can be divided into AC and DC types according to the load power supply type. According to the switch type, they can be divided into normally open type and normally closed type. According to the isolation type, they can be divided into hybrid type, transformer isolation type and photoelectric isolation type, with photoelectric isolation type being the most common.