Main classification functions: 1. Electrical appliances used to connect and disconnect circuits, such as contactors, knife switches, load switches, isolation switches, circuit breakers, etc; 2. Electrical appliances used to control circuits, such as electromagnetic starters, self coupling voltage reducers, varistors, control relays, etc; 3. Electrical appliances used for switching circuits, such as transfer switches, master appliances, etc; 4. Electrical appliances used to detect circuit coefficients, such as transformers, sensors, etc; 5. Electrical appliances used to protect circuits, such as fuses, circuit breakers, lightning arresters, etc. Circuit function classification 1. Control electrical appliances: including contactors, switching appliances, control relays, master electrical appliances, etc. It mainly plays a control and conversion role in the circuit; 2. Protective electrical appliances: including fuses, thermal relays, overcurrent relays, undervoltage relays, overvoltage relays, etc., which play a protective role in the circuit. Classification of action principles: 1. Electrical appliances, such as manual switches, control buttons, travel switches, and other master electrical appliances; 2. Electrical appliances that operate automatically due to changes in electromagnetic force or a certain physical quantity, such as contactors, various types of relays, solenoid valves, etc. Usage classification 1. Control appliances: electrical appliances used in various control circuits and control systems, such as contactors, relays, motor starters, etc; 2. Master electrical appliances: electrical appliances used in automatic control systems to send action instructions, such as buttons, travel switches, universal transfer switches, etc; 3. Protective appliances: Electrical appliances used to protect circuits and electrical equipment, such as fuses, thermal relays, various protective relays, lightning arresters, etc; 4. Executive electrical appliances: refer to electrical appliances used to complete a certain action or transmission function, such as electromagnets, electromagnetic clutches, etc; 5. Distribution appliances: Electrical appliances used for the transmission and distribution of electrical energy, such as high-voltage circuit breakers, isolation switches, knife switches, automatic air switches, etc. Working principle classification: 1. Electromagnetic electrical appliances: operate based on the principle of electromagnetic induction, such as contactors, various types of electromagnetic relays, etc; 2. Non electric quantity control electrical appliances: Electrical appliances that operate by relying on external forces or changes in certain non electric physical quantities, such as knife switches, travel switches, buttons, speed relays, temperature relays, etc. Functional classification of low-voltage electrical appliances 1. Switching appliances: electrical appliances that connect and disconnect circuits and have a certain ability to make and break, such as transfer switches, starters, etc; 2. Fuses: Electrical appliances that break circuits under overload or short circuit conditions, such as high breaking capacity fuses, self resetting fuses, etc; 3. Relay: an electrical device used for control and protection; 4. Resistors and varistors: Electrical appliances that change circuit parameters or convert electrical energy into thermal energy, such as starting resistors, regulating resistors, starting varistors, excitation varistors, etc; 5. Regulator: An electrical device that maintains certain quantities in a circuit or causes them to change in a predetermined manner; 6. Electromagnet. Functional classification of high-voltage electrical appliances: 1. Switching appliances: mainly include high-voltage circuit breakers, high-voltage isolation switches, high-voltage fuses, high-voltage load switches, and grounding short circuiters. High voltage circuit breakers are used to connect or disconnect circuits under no-load, normal load, or short-circuit fault conditions. The high-voltage isolation switch is used to isolate live high-voltage electrical equipment from the power supply, and generally only has the ability to open and close no-load circuits. High voltage fuses are used to break circuits under overload or short circuit conditions. The high-voltage load switch is used to connect or disconnect circuits under no-load, normal load, and overload conditions, and is usually used in conjunction with high-voltage fuses. The grounding short circuit breaker is used to artificially short circuit high-voltage lines to ground. 2. Restrict electrical appliances. Mainly including reactors and lightning arresters. 3. Transformer, also known as transformer. [1]