Electromagnetic relays refer to relays made using the principle of electromagnetic induction. When the relay is energized, the coil of the relay generates electromagnetism, which closes the normally open contacts of the relay to work.
what is a relay
Definition of relay: A relay is an automatic control device whose output will change in leaps and bounds when the input (electricity, magnetism, sound, light, heat) reaches a certain value.
The working principle and characteristics of the relay
When the input quantity (such as voltage, current, temperature, etc.) reaches a specified value, the controlled output circuit is turned on or off. 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. 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 input circuit) and a controlled system (also known as output circuit), usually used in automatic control circuits, it actually uses a smaller current to control a larger An "automatic switch" of electric current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.
Principle of Electromagnetic Relay
When voltage or current is applied to both ends of the coil lead-out pin, the excitation current of the coil generates magnetic flux, and the magnetic flux passes through the magnetic circuit composed of iron core, yoke iron, armature and working air gap, and generates electromagnetic attraction in the working air gap. When the excitation current rises to a certain value, the electromagnetic attraction torque will overcome the counter torque of the moving spring to make the armature rotate, and drive the push piece to push the moving spring to realize the contact closure; when the exciting current decreases to a certain value, the counter torque of the moving spring will The armature returns to its initial state when it is greater than the electromagnetic suction torque, and the contacts are disconnected.
2. Working principle of magnetic latching relay
The state retention force of the relay contact is produced by two pieces of magnetic steel in the armature part. The magnetic flux generated by the magnetic steel passes through the right armature-yoke iron pole-iron core-yoke iron pole-left armature-magnet to form a closed loop, in the armature As shown in the figure, the extension arm of the left armature exerts a thrust on the moving reed through the pushing piece, so that sufficient pressure is generated between the moving and static contacts, so that it can carry current reliably.
When the relay contact needs to be disconnected, it is only necessary to apply a pulse voltage of sufficient width to the coil. The magnetic flux generated by the pulse voltage is opposite to the magnetic flux generated by the magnetic steel, and the same pole as the magnetic steel will be generated on the magnetic pole. According to the principle of repulsion of the same magnetic field, a thrust will be generated between the armature and the yoke iron poles. When the synthetic torque generated by the magnetic circuit is greater than the counter torque of the reed, the moving spring will move backwards, and the armature will rotate around the shaft, and the relay will appear as shown in the figure 3 in the disconnected state. If you want to return to the closed state, you must apply an opposite pulse to the coil, otherwise, the relay contact state will remain forever
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