ECE-2p DC contactor-Monthly Review

2p DC contactorLike electromechanical relays, they have physical contacts that are mechanically driven to open/close paths. However, for reed relays, their contacts are much smaller and of much lower quality than those in electromechanical relays. Dry reed relays are made of coils wound around reed switches. The mechanical lifespan of electromechanical relays is usually shorter than other types of relays. The advancement of technology has increased their mechanical lifespan, but electromechanical relays still do not have as many actuators as comparable reed relays.A magnetic reed switch consists of two overlapping ferromagnetic blades (known as magnetic reeds) that are sealed inside a glass bag filled with inert gas. The overlapping ends of reeds have contact. When the coil is energized, the two springs are pulled together, forming a path through the relay at their contacts. When the coil is powered off, the spring force in the spring will pull the contacts apart.

Due to smaller contacts, lower weight, and different actuators, the switching speed of reed relays is about 10 times faster than electromechanical relays with the same rated value. The mechanical lifespan of reed relays is also higher than that of electromechanical relays. However, the compromise solution is that the smaller contacts on the reed relay make it more susceptible to arc damage when closing the circuit. When the arc jumps across the contact point, a small portion of the contact surface will be melted. If the contacts remain closed during the re solidification of the melting section, they may be welded together. After turning off the driving current, the spring force in the spring is usually insufficient to mechanically disconnect the weld seam, which makes the relay unusable. Electromechanical relays may also be damaged due to arcing, but the energy required to cause this situation is much higher.

Due to the high susceptibility of reed relays to contact damage, surge currents from system capacitors can be particularly dangerous. Surge current can be controlled through the series impedance between relays and capacitors, such as resistors or ferrites. Any capacitor in the system can cause surge currents, whether it is in the tested electrical resistance device or from shielded cables.

constitute2p直流接觸器The ferromagnetic material gives them a higher thermoelectric potential than equivalent electromechanical relays.Like any relay, the amount of power to be switched and other system considerations may have a significant impact on the overall lifespan of the relay. In fact, the mechanical life of electromechanical relays may be shorter than that of reed relays, but the electrical life under similar loads (especially capacitive loads) may decrease at a much slower rate than that of reed relays. The larger and more robust contacts of electromechanical relays are usually more durable than similar reed relays. Therefore, reed relays are not an ideal choice for extremely low voltage applications, as their thermoelectric potential may introduce sufficient noise, leading to measurement errors.

The small size and high speed of reed relays make them an ideal choice for many switch applications. Compared to general modules, reed relays are more common on matrix and multiplexer modules.