The YB-50 and 200 microcomputer integrated motor protection relays use the PIC microcontroller produced by the internationally renowned Microchip company as the core component. The products are completely digitally controlled and detect current signals through built-in high-precision current transformers; A mathematical model established based on the heating characteristics of electric motors can provide good protection for various AC motors that may experience faults such as phase failure starting, locked rotor, grounding, overcurrent, undercurrent, phase failure operation, and low-voltage three-phase imbalance caused by high-voltage side phase failure of power transformers; Multiple functions can be set (overcurrent, undercurrent, leakage current, three-phase imbalance, starting delay, overcurrent protection characteristics, etc.), with high setting accuracy, wide range, and simple operation; The digital display shows the operating current of the motor, without the need for an external current transformer. The current range includes 1-200A, and it can achieve motor reclosing (shaking and then tripping). And it has a 4-20mA transmission output port, which can also accumulate the total running time of the motor and achieve star delta conversion control. The product follows the installation structure of a thermal relay, and the main circuit adopts a perforated design to avoid contact and heat generation with the main circuit. It can cooperate with any contactor to form an electric motor protection system and is suitable for installation in drawer cabinets.