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What is a magnetic latching relay?

From: Quisure2020-09-02

Magnetic latching relay is a new type of relay developed in recent years. It is also an automatic switch. Like other electromagnetic relays, it can switch on and off the circuit automatically. The difference is that the normally closed or normally open state of magnetic latching relay completely depends on the action of permanent magnet, and the switching state of magnetic latching relay is triggered by a certain width of pulse electric signal. (How to choose a relay?)

What is a magnetic latching relay?

Magnetic latching relay is divided into single-phase and three-phase. According to relevant information, the maximum contact switching current of magnetic latching relay on the market can reach 150A; the voltage of control coil is divided into dc9v, DC12V, etc. General electrical life is 10000 times; mechanical life is 1000000 times; contact voltage drop is less than 100mV. Therefore, it has the characteristics of power saving, stable performance, small size, large bearing capacity and superior performance than general electromagnetic relay.

Magnetic latching relay is mainly used in IC card prepayment meter and centralized meter reading system. In recent years, magnetic latching relay has been widely used in the composite switch of reactive power compensation device. In combination with thyristor, it has become the main switching device in reactive power compensation device to switch large current circuit. It can also be used in various household appliances and automatic control devices (such as lighting control system).

What is a magnetic latching relay?

Advantages of magnetic latching relay

1. It can work with single or double coils only by pulse excitation.

2. Small size, PCB type installation.

3. Low power consumption, strong load capacity.

4. Safe and reliable, long life.

Structure of magnetic latching relay

The magnetic latching relay is divided into two layers, the upper layer is the electromagnetic system, and the lower layer is the contact system. The electromagnetic system adopts the flat direct acting magnetic circuit system, which includes magnet, coil, armature, iron core and mounting plate. The magnet is located in the center of the mounting plate, and coils are installed on both sides of the magnet. The U-shaped iron core is set above the coil, and the armature is in the iron core to form an annular structure It can be controlled by magnetic field. Both ends of the mounting plate are located beside the U-shaped bottom of the iron core, and a pure iron plate is also installed to prevent the interference of external magnetic field. 

Principle of magnetic latching relay

The open and closed state of the magnetic latching relay is usually held by the magnetic force generated by the permanent magnet. When the contacts of the relay need to be opened or closed (i.e. when the load is connected or cut off), the relay can complete the state transition of opening and closing in an instant by using the positive (negative) DC pulse voltage to excite the coil. The power loss is generally less than 1W. Usually, when the contact is in the hold state, the coil does not need to continue to be energized, and the state of the relay can be maintained only by the magnetic force of the permanent magnetic steel.

Function of magnetic latching relay

Relay is an automatic switching element with isolation function, which is widely used in remote control, telemetry, communication, automatic control, mechatronics and power electronic equipment, and is one of the most important control elements.

Generally, relays have induction mechanism (input part) which can reflect certain input variables (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.); there are actuators (output parts) that can realize "on" and "off" control of controlled circuit; between the input part and the output part of the relay, there is an intermediate mechanism (drive part) for coupling and isolating the input, function processing and driving the output part.

1. Expand the scope of control. For example, when the control signal of multi-contact relay reaches a certain value, the multi-channel circuit can be changed, disconnected and connected according to different forms of contact groups.

2. Zoom in. For example, sensitive relay, intermediate relay and so on, with a very small amount of control, can control a high power circuit.

3. Integrated signal. For example, when multiple control signals are input into multi winding relay according to the prescribed form, the predetermined control effect is achieved through comparison and synthesis.

4. Automatic, remote control and monitoring. For example, the relay on the automatic device and other electrical appliances can form a program control circuit to realize automatic operation.

Application precautions of magnetic retaining relay

1. The factory status of the magnetic retaining relay is usually contact closed, but may change due to factors such as transportation or impact during relay installation.Therefore, it is necessary to take measures to reset the contacts before use.

2. In order for the relay to operate reliably, the voltage applied to the coil must reach the rated voltage and the pulse width must be more than three times the operating time.

3.Magnetic Relay coils are polar differentiated and coil polarity must be specified when ordering.

4. The shape and installation size of magnetic retaining relay can not be changed generally. During selection, attention should be paid to whether the relay shape size meets the requirements.The peripheral accessories of the relay are customizable.For double-hard-connected products, one side of the lead-out conductive strip must be flexible; if both sides are rigid, the relay is prone to high stress after installation, which may change the parameters of the relay.

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