Difference between relays KA and KM

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The difference between relays KA and KM: KA is generally an intermediate relay, while KM or K refers to a contactor. KA is a special type of contactor (i.e., a switch). It has 4 sets of normally closed angular contacts on the top and 4 sets of normally open angular contacts on the bottom. When the coil is energized, electromagnetic force pulls the moving iron downward, causing the 4 sets of normally closed angular contacts on the top to separate while the 4 sets of normally open angular contacts on the bottom close. It is used to transmit intermediate signals in control circuits. The structure and principle of an intermediate relay are basically the same as those of an AC contactor. The main difference between them is that the main contacts of a contactor can carry large currents, while the contacts of an intermediate relay can only carry small currents. Therefore, it can only be used in control circuits. KM contactors are used to connect and disconnect loads. It is combined with a thermal overload relay to protect electrical equipment in operation. It is combined with relay control circuits to remotely control or interlock related electrical equipment. AC contactors: The typical structures are divided into the double-break direct-acting type (LC1-D/F*) and the single-break rotary type (LC1-B*). The former has a compact structure, small size, and light weight ； The latter is easy to maintain and can be configured in single-pole, two-stage, and multi-pole configurations, but it has a large size and requires significant installation space. DC contactors: Their operating principle is similar to that of AC contactors, but when breaking a DC circuit, the magnetic field energy stored in inductive loads is released instantaneously, resulting in a high-energy arc at the break point; therefore, DC contactors need to have certain arc-extinguishing capabilities. Medium/large capacity DC contactors typically adopt a single-breakpoint, planar layout with an integrated structure; their feature is a long arc distance during disconnection, and the arc extinguishing chamber contains arc extinguishing grids. Small-capacity DC contactors feature a dual-breakpoint three-dimensional layout structure. Vacuum contactor: The components of a vacuum contactor (LC1-V*) are similar to those of ordinary air-type contactors; the difference is that the contacts of a vacuum contactor are sealed inside a vacuum arc extinguishing chamber, which allows it to handle higher currents and operate at higher rated voltages. Semiconductor contactors: Key products such as bidirectional thyristors are characterized by the absence of moving parts, long service life, fast response times, resistance to explosions, dust, and harmful gases, as well as durability against impact and vibration.