Engineer story sharing(1)

Experience and lessons on self-control roads 

In the first year, I joined the work. Because the copper nose was too long when the big motor was on the copper nose, the cable was thicker. It was not good in the junction box. It took a lot of effort. At that time, I thought it was tightened. Later, after running, The terminals and cables are hot, the terminals are softened, the screws on the terminals are loose, causing sparks, and the motor is almost burnt. Therefore, when connecting a large motor, the motor must be tightened regularly for a period of time.

Once, because the construction team did not press the copper nose, the 280kw motor was running, the junction box was on fire, the cable was blown, the terminal was blown, and the motor winding insulation was burned out.
A colleague picked up the temporary line on the copper platoon, did not tighten the copper nose fastening screw, and heated for a long time. Finally, an arc was formed, and the copper platoon of 120 was burned a large hole, causing the workshop equipment to stop working.
When the busbar is not suitable for the cabinet, the construction side saws it with a hacksaw. The copper scraps fall into the isolating switch, and the other party is required to use the insulation shaker for insulation testing. The other party only promises not to do it. After the power transmission, the isolating switch The upper phase is short-circuited, the isolating switch is burnt, the mounting plate is burnt, and the small busbar is blown.
Once the electricity is temporarily used, there is no temporary cable. The 240-square-wide cable is used. Because the length of the cable is very small, only a part of the cable is pulled apart, and the cable is also wound into a coil. The electric equipment is mainly an electric welder. Mainly, the cable over-current is large, resulting in the formation of eddy currents in the middle of the cable tray. Just in midsummer, there are heat waves coming from far away.
The motor tripping fault of the graphite mixing workshop can not find the cause. It is suspected that it is caused by graphite, causing the circuit breaker or the contactor to form a short circuit. How can it not be measured with the multimeter, but it will trip when the power is sent, and finally understand that the multimeter has no voltage. Phases are not broken down by high voltage. After the switch-on, the phase 380v voltage is broken down. From then on, there is insulation feeling, and the insulation is relative voltage.
At the time of graduation, the zero line was the line with zero voltage. Once I saw the zero line of a light bulb in the electrical cabinet, I touched it by hand. After I got an electric power, I realized that the original zero line was not overloaded. It is the zero line, and the zero line is connected to the working zero line to calculate the zero line.
One colleague connected the miniature circuit breaker, and the bus bar used at the top was plugged in with a hacksaw and then plugged in. As a result, the switch was tripped. When the sawing bus was cut, a short circuit was formed between the three busbars at the incision. From then on, I understand that after the bus bar is cut, the excess part should be cut off. Do not expose the copper bar at both ends.
Once in a factory, the project was done well during the day. At 12 o'clock in the evening, the operator called to say that the inverter was faulty. The original inverter reported a voltage fault. Finally, I figured out that due to the large amount of electricity during the day, the grid The voltage is low, some factories will adjust the voltage of the transformer twice to a little higher. After the night, the grid voltage is high, and the voltage of the transformer is also increased at the same time. .
After one factory repairs the power supply of a workshop, it is not connected back according to the original phase sequence, causing the equipment to reverse, some equipment motors are burned out, and the electric push rod with limited position loses the limit protection or burns or trips. From then on, the distribution phase sequence cannot be easily exchanged.
Once a new motor is sent to the point and then tripped, it is found that the insulation resistance is not enough. From then on, remember to check the insulation before wiring the motor.
Once the inverter reported a high temperature fault, the test found that there was too much dust in the inverter, blocking the ventilation and circulation, and understood that the electrical equipment must be cleaned regularly.
One 24V timer at a time, do not want to stop, live operation, the result is not properly taken off the 220 fire line, causing the PLC analog module to burn, the vibration sensor burned. Was fined by the boss and lowered his salary. Deeply remember, to operate according to the specifications, the wiring inside the cabinet should try not to leak the conductor to prevent accidents.
One factory once did the ingredients project, and one colleague was killed by high voltage electricity. When two colleagues found that the silo could not be lowered, they carried an angle steel to pick up the material. They did not pay attention to the surrounding high-voltage line. The angle steel hit the high-voltage line, causing the former colleague to die. Because a colleague in front was penetrated, the ground was turned on first. A colleague survived and was scared. From then on, remember to observe the surrounding live equipment before work, pay attention to the potential danger when working.
Once the PLC transistor output is connected to the relay, the PLC output board is directly on fire due to the positive and negative connection on the relay. It is remembered that the output of the transistor is different from the relay output. If the PLC is connected incorrectly, it must be burned. Although it is only a problem with the Panasonic PLC and the Panasonic relay connected, do not pick up the wrong one.
Relay control electric valve burning contact, electric contact pressure gauge contact relay electrical contact is easy to carbonize, understand the arc damage to the contact, in the control of the original selection, not only must consider the current, voltage, but also consider the inductance, according to AC1, AC2, AC3, AC4 and other equipment categories, use different electrical originals.