All equipment is subject to aging and deterioration during use. This is obvious in mechanical equipment, but difficult to observe in electrical equipment. For motor, transformer, reactor and other equipment, temperature and electrical characteristics such as coil resistance, insulation resistance to ground, and current changes can be observed, but the deterioration of electronic equipment is difficult to monitor. Therefore, electrical equipment needs to pay attention to daily maintenance to reduce or even eliminate the occurrence of accidents. Equipment maintenance includes online maintenance and offline maintenance. Some large equipment needs online maintenance. If conditions permit, it is better to replace small and medium-sized equipment for off-line maintenance. During the use of electrical equipment, temperature and dust are fatal hazards to electrical equipment.
It is mainly shown in the following aspects: 1. High temperature will damage the insulation of electrical equipment, causing short circuit or grounding. High temperature of equipment directly burned is mainly caused by the heating of equipment itself and high ambient temperature on site. During the use of the equipment, it is necessary to ensure that its rated load cannot be exceeded. Although a reasonable power has been calculated in the initial design, the aging of mechanical equipment during the use will also lead to overload of electrical equipment. This requires close coordination with mechanical equipment. Although the widespread use of some thermal protection devices and over-current protection devices makes it possible to stop in time in case of overload, after all, the equipment is also subject to the impact of high current, which leads to the deterioration of the equipment over time. It is necessary to record the current and temperature observed daily in real time to facilitate analysis, find out the equipment with large current (relative to the rated value) and high temperature, and focus on its inspection during shutdown. For motors and reactors, the resistance and insulation resistance of the above equipment and some key equipment shall be measured each time the equipment is shut down.
Regular measurement is also required for ordinary equipment. Record the measured values and make a chart or curve to detect the deterioration. According to the actual production situation, the equipment shall be replaced regularly and maintained after offline. The heating of electronic equipment is caused by power components, mainly diodes, silicon controlled rectifier, etc. There are usually cooling fans, and some large equipment is also water-cooled. For the cooling devices of large equipment, there are online monitoring sensors for temperature, air pressure, water pressure, flow and so on. If there is a problem with the monitored data, the machine will be shut down in time. These parts shall be inspected when the equipment is shut down. The bolts at the copper bar connection or wiring part of the electrical equipment will also become loose after a long time of use, resulting in improper contact and heating. During the daily point inspection, it is necessary to measure the temperature with a temperature measuring gun. If the temperature rises, it is necessary to apply for shutdown in time.
2. Dust At present, many factories are implementing the spot inspection and regular repair system, in which cleaning is particularly important for electrical equipment. Dust will affect the heat dissipation effect of the equipment. The dust in some factories contains metal particles, which will directly cause short circuit if attached to electronic components. Although most of these devices are installed in the power distribution room, dust will also enter. During the daily maintenance, the electronic equipment shall be dedusted and cleaned regularly.
The main steps are as follows: 2.1 The dedusting of electronic equipment mainly refers to online maintenance, such as frequency converter. First, cut off the power supply in the shutdown state, wait for 2-3 minutes, and then operate after the discharge is completed. The rubber tube of the blower can be extended into the device to blow out the dust. The most dust is on the power section and cooling fan. If necessary, open the shell of the device and blow the circuit board and silicon directly. It is important not to touch the components inside. This step should be done by professionals.
For online dedusting of large motors and transformers, due to the need for air cooling, if the air quality is poor, dust will be brought into the interior of the motor. In addition, the powder after the motor carbon brush is worn will also enter the motor, so regular dedusting is required. At this time, the air pressure of ordinary fan is low, and it is difficult to clean, so compressed air should be used for purging. Normally, the commutator of DC motor is golden yellow, with oxide film formed on the surface. The powder after carbon brush wear is stuck to the commutator and the commutator groove, making the commutator black, which may cause the motor to ignite or even burn the commutator in serious cases. In this case, the carbon powder cannot be blown off with compressed air. It is necessary to use a clean white cloth dipped with detergent or alcohol to wipe off the carbon powder stuck on the commutator, and then use a hook made of a hacksaw blade to hook the carbon powder out of the commutator groove. The oxide film on the commutator surface may be damaged after completion, and the load should be gradually increased after a period of operation under low load. In addition, the carbon brushes shall be replaced regularly during the maintenance of DC motor. The direction of carbon brushes shall be paid attention to and they shall be replaced in batches as much as possible. The tip of the new carbon brush shall be polished off in advance according to the arc of the commutator, and the pressure of the top spring shall not be adjusted randomly as far as possible. For the maintenance of equipment, special record accounts must be formed, such as Insulation Resistance Telemetry Record, Equipment Replacement Account, Equipment Cleaning and Dedusting Account, Patrol Point Inspection Record, Equipment Test Record, etc., and the responsibility should be assigned to people, not just in a formality. Only when the work is done carefully can the equipment be well maintained.
Some of the above experience in equipment maintenance needs to form a normal mode in daily production, so that data is recorded, and replacement and maintenance accounts are kept. When conditions permit, the equipment after maintenance shall be tested offline before going online to ensure the normal use of spare parts. Only constant efforts can ensure the normal operation of online equipment and smooth production.
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