Abstract : Taking a small, high-sensitivity electromagnetic relay as an example, this article illustrates how an asymmetrical magnetization method and altered pole shoe area are used in the dual-air-gap magnetic circuit system of the "rocker-type" balanced armature structure in traditional polarized relays to enable the polarized relay to produce monostable functionality. This achieves the goal of reducing power consumption and improving relay sensitivity, thus realizing the optimal design of a small, high-sensitivity relay using a polarized relay structure to achieve its intended function. Keywords : Electromagnetic relay; Sensitivity; "rocker-type" balanced armature; Polarized relay 1 Introduction Relays are key components in electronic equipment, industrial automation control systems, and power system relay protection devices, playing a crucial role in control, information transmission, and switching. With the rapid development of aerospace technology, applications such as supersonic aircraft, missiles, artificial satellites, and spacecraft place higher demands on relays, requiring high reliability, high sensitivity, and high-density installation. To address this, we developed a novel ultra-miniature relay. This relay is small in size (15.5mm × 8.2mm × 8.2mm), highly sensitive, consumes only 80mW, has a maximum switching current of 0.5A, a maximum switching voltage of 28V, DC, and a vibration frequency of 10Hz-3000Hz, 294m/s². 2. Related Theories In electromagnetic relays, common electromagnetic system forms include four types: snap-fit ​​type, solenoid type, balanced rotary type, and balanced force type. The balanced rotary type structure has two series-connected working air gaps, characterized by symmetrical armatures rotating around a fixed axis, as shown in Figure 1. This structure, due to its balanced armature mass distribution, has good vibration and shock resistance, and its compact structure makes it easy to achieve miniaturization. However, in general electromagnetic relay technology, when the coil space within the relay is limited, reducing the relay's external volume while simultaneously achieving high sensitivity is theoretically contradictory. (The text then abruptly shifts to a seemingly unrelated topic about a factory's electromagnetic relay design.) Taking the 200M relay as an example, the electromagnetic system of this product is a balanced rotary structure (as shown in Figure 1). Its attraction-reaction characteristic curve is shown in Figure 2. When the operating voltage is at a certain value, the electromagnetic attraction curve and the mechanical reaction curve intersect at a point. If the correction value is below this value, the attraction characteristic curve and the reaction characteristic curve will inevitably intersect. This is because the reaction force of the return spring is too large in the attracted state, causing the armature to do more work to overcome the reaction force of the return spring during the closing process, thus reducing the sensitivity of the relay. However, if the reaction force is reduced, the holding force of the armature in the released state will be insufficient, and the vibration resistance will be low. Therefore, the main drawback of the magnetic circuit of this electromagnetic relay is that the sensitivity of the magnetic system cannot be effectively improved. It is difficult to improve the sensitivity of the product by relying on this magnetic circuit structure. [b][align=center]For details, please click: Design of Ultra-Miniature High-Sensitivity Electromagnetic Relay[/align][/b]