Basic knowledge of electrician

The electrician's basic knowledge includes: left zero and right fire, transformers in operation, and the phase currents of transformers should not exceed the rated current. Transformers should be overhauled regularly after being put into operation. In the same transformer power supply system, it is not appropriate to mix protective grounding and protective grounding. The rated voltage of the secondary coil of voltage transformer is 100V, and the secondary side of voltage transformer should not be short-circuited during operation.

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.

One end of the secondary side of voltage transformer must be grounded.

When the current transformer is working, the secondary side is close to short circuit.

When working, the secondary side of the current transformer shall not be open.

One end of the secondary side of the current transformer must be grounded to prevent the high voltage from the primary side from entering the secondary side when the insulation of its primary and secondary coils is broken down.

When connecting current transformers, we should pay attention to the polarities of their primary and secondary coils. In China, transformers are labeled with decreasing polarity.

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.

Low-voltage switches refer to disconnectors, circuit breakers and fuses below 1KV.

The load controlled by low-voltage distribution equipment must be clearly divided, and it is forbidden to control more than one brake, which is confusing.

Interlocking devices for 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.

Insulating pads should be laid on the channels for front, back, left and right operation and maintenance of low-voltage distribution equipment, and other items are strictly prohibited to be stacked on the channels.

Connect the equipment first, and then connect the power supply.

Please cut off the power supply before disassembling the equipment.

When connecting lines, connect the neutral line first, and then the live line.

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

Low-voltage fuses cannot be used as overload protection for motors.

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

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

The breaking capacity of the fuse must be greater than the maximum short-circuit current that may occur in the distribution line.

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

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

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