Electricians are divided into five levels. Skills are identified as: primary skills (level 5 qualification), intermediate skills (level 4 qualification), advanced skills (level 3 qualification), technicians (level 2 qualification) and senior technicians (1 level qualification). Today I'm going to talk about the basics of electrician. Welcome to reading. It is really hard to learn practical knowledge with such sincerity. Electricity, a mature and systematic subject, has a complete set of theories supported by mathematics. The knowledge of electrical theory used by electricians is also inseparable from the mathematical foundation. As the old saying goes, "If you know why, you should also know why". What you have to do now is to "know what it is"-learn the actual operation from the master. After the operation, you will ask "why?" This may need the theory of electricity to explain. Then, you will learn the corresponding theoretical knowledge to the extent of "knowing why". Before learning the theoretical knowledge of electrical engineering, I suggest you review the mathematics in junior high school, which is often needed when learning the theoretical knowledge of electrical engineering.

1, left zero right fire.

2. The yellow, green, red and light blue used in the three-phase five-wire system respectively represent the two colors (PE) of U, V, W and N protective grounding wires.

3, transformer in operation, the transformer phase current should not exceed the rated current; The maximum unbalanced current shall not exceed 25% of the rated current. After the transformer is put into operation, it should be overhauled regularly.

4. In the power supply system of the same transformer, protective grounding and protective zero connection should not be mixed.

5. The rated voltage of the secondary coil of the voltage transformer is generally100V. ..

6. The secondary side of voltage transformer should not be short-circuited at work. Because of short circuit, a large short circuit current will be generated, which may burn out the transformer. Therefore, both the primary side and the secondary side of the voltage transformer are equipped with fuses for protection.

7. One end of the secondary side of voltage transformer must be grounded. This is to prevent the primary high voltage from entering the secondary side when the insulation of the primary and secondary coils is broken down, endangering personal and equipment safety.

8. When the current transformer is working, the secondary side is close to short circuit. The rated current of the secondary coil is generally 5A.

9. The secondary side of current transformer shall not be open at work.

10, one end of the secondary side of the current transformer must be grounded to prevent the high voltage on the primary side from entering the secondary side when the primary and secondary coils are insulated and broken down.

1 1. When connecting the current transformer, pay attention to the polarities of its primary and secondary coils. In China, transformers are labeled with decreasing polarity.

12, when installing, be sure to pay attention to the correct and reliable wiring, and the secondary side is not allowed to be connected with fuses or switches. Even if the instrument or other equipment on the secondary side is to be dismantled for some reason, the secondary side must be short-circuited first, and then dismantled.

13, low-voltage switches refer to disconnectors, circuit breakers, fuses, etc. below 1KV.

14, the load controlled by low-voltage power distribution equipment must be clearly divided, and it is forbidden to control more than one brake and use it confusedly.

15. Interlocking devices of low-voltage power distribution devices and self-provided generator equipment shall be reliable. It is forbidden to run self-provided power generation equipment in parallel with the power grid privately.

16. Insulating mats should be laid on the passages for operation and maintenance of low-voltage distribution equipment, and other articles are strictly prohibited to be piled on the passages.

17. When connecting equipment: connect the equipment first, and then connect the power supply.

18. When disassembling the equipment: disassemble the power supply first, and then disassemble the equipment.

19. When connecting the line: connect the neutral line first, then the live line.

20. When disconnecting the line: disconnect the live line first, and then disconnect the zero line.

2 1, low-voltage fuse cannot be used as overload protection of motor.

22. The rated voltage of fuse must be greater than or equal to the working voltage of distribution line.

23. The rated current of fuse must be greater than or equal to the rated current of melt.

24. The breaking capacity of the fuse must be greater than the possible maximum short-circuit current of the distribution line.

25. The selection of rated melt current must meet the normal working current of the line and the starting current of the motor.

26. For short-circuit protection of electric furnace and lighting load, the rated current of the melt is equal to or slightly greater than the rated current of the load.

27. For a single motor, rated melt current ≥( 1.5-2.5) rated motor current.