Maintenance method and practice of air compressor electrical equipment

Maintenance method and practice of air compressor electrical equipment

There are many commonly used electrical equipment, such as circuit breakers, contactors, relays, thermal relays, switches, etc., these are hard circuits, in addition to PLC, etc., these equipment is very widely used in air compressors and station rooms, it can be said to be necessity. Therefore, a proper grasp of the principles and methods of failure maintenance of common electrical equipment is very helpful to improve the efficiency and professionalism of air compressor operation and maintenance personnel.

1. Ten principles of electrical equipment maintenance

1. First move your mouth and then move your hands

For electrical equipment with faults, do not rush to do it, you should first ask about the process of the fault and the phenomenon of the fault. For unfamiliar equipment, you should also be familiar with the circuit principles and structural features and follow the corresponding rules. Before disassembling, be fully familiar with the function, position, connection mode and relationship with other surrounding components of each electrical component. If there is no assembly drawing, draw sketches and mark while disassembling.

2. First outside, then inside

Check the equipment for obvious cracks and defects, understand its maintenance history, service life, etc., and then inspect the inside of the machine. Before dismantling, you should queue up the surrounding fault factors, and dismantle it only after determining that it is an internal fault. Otherwise, blind dismantling may cause the equipment to become more damaged.

3. Mechanical first, electrical

Only after confirming that the mechanical parts are not faulty, conduct electrical inspections. When inspecting circuit faults, you should use the detection instrument to find the fault location, confirm that there is no bad contact fault, and then check the operation relationship between the circuit and the machine in a targeted manner to avoid misjudgment.

4. First static and then dynamic

When the equipment is not powered on, judge the quality of the buttons, contactors, thermal relays and fuses of the electrical equipment to determine the fault. Power-on test, listen to the sound, measure the parameters, judge the fault, and finally repair it. For example, when the motor is lacking phase, if the measurement of the three-phase voltage value cannot be distinguished, you should listen to it and measure each phase to ground voltage separately to determine which phase is defective.

5. Clean first and then repair

For electrical equipment with heavy pollution, clean the buttons, wiring points, and contact points first, and check whether the external control keys fail. Many faults are caused by dirt and conductive dust, and the faults are often eliminated after cleaning.

6. Power first, then equipment

The failure rate of the power supply part occupies a high proportion of the entire faulty equipment, so the power supply can often be twice the result with half the effort first.

7. First general and then special

Failures caused by the quality of assembly parts or other equipment failures generally account for about 50% of common failures. The special faults of electrical equipment are mostly soft faults, which require experience and instruments to measure and maintain.

8. Peripheral first, then internal 　

Do not rush to replace the damaged electrical components. When confirming that the peripheral equipment circuit is normal, consider replacing the damaged electrical components.

9. When overhauling from DC to AC, the static operating point of the DC loop must be checked first, and then the dynamic operating point of the AC loop.

10. Debug after failure

2. Inspection method and operation practice

1. Intuitive method

The intuitive method is a method of checking and judging faults based on the external manifestations of electrical faults by looking, smelling, and listening.

(1) Inspection steps:

　Investigation: Ask the operator and the personnel present at the fault about the situation, including the external appearance of the fault, the general location, and the environmental conditions at the time of the fault. If there is abnormal gas, open flame, whether the heat source is close to the appliance, whether there is corrosive gas intrusion, whether there is water leakage, whether someone has repaired it, the content of the repair, etc.

Preliminary inspection: According to the investigation, check whether the relevant electrical appliances are damaged, whether the wiring is broken or loose, whether the insulation is burnt, whether the fuse indicator of the screw fuse jumps out, whether the electrical appliance has water or grease, and the switch position Is it correct?

Test run: After the preliminary inspection has confirmed that the fault will further expand and cause personal and equipment accidents, further test run inspections can be carried out. During the test run, pay attention to whether there are serious flashovers, abnormal smells, abnormal sounds, etc., and stop immediately when found. Cut off the power. Pay attention to check whether the temperature rise of the electrical appliance and the action program of the electrical appliance meet the requirements of the electrical equipment schematic diagram, so as to find the fault location.

(2) Inspection method: 　observe sparks: sparks will be generated when electrical contacts are closed, breaking circuits or wire ends are loose. Therefore, electrical faults can be checked based on the presence and size of sparks. For example, when a spark is found between a normally tightened wire and a screw, it indicates that the wire end is loose or has poor contact. The electrical contacts flash when the circuit is closed or break, indicating that the circuit is on, and if there is no flash, the circuit is not working. When the main contact of the contactor of the control motor has sparks in two phases and no spark in one phase, it indicates that the non-sparking one-phase contacts are in poor contact or the circuit of this phase is open; the sparks of two of the three phases are larger than normal, and the other phase If it is smaller than normal, it can be preliminarily judged that the motor is short-circuited or grounded; the three-phase sparks are larger than normal, which may be the motor is overloaded or the mechanical part is stuck. In the auxiliary circuit, after the contactor coil circuit is energized, the armature does not pull in. It is necessary to distinguish whether the circuit is broken or the mechanical part of the contactor is stuck. You can press the start button. If there is a slight spark when the closed position of the normally open contact of the button is opened, it indicates that the circuit is connected and the fault is in the mechanical part of the contactor; if there is no spark between the contacts, the circuit is open.

　Operation procedure: The operation procedure of the electrical appliance should meet the requirements of the electrical manual and drawings. If the electrical action on a certain circuit is too early, too late or inactive, it means that the circuit or electrical device is faulty.

　In addition, it can also analyze and judge the fault based on the sound, temperature, pressure, smell, etc. of the electrical appliance. Using intuitive methods, not only can simple faults be identified, but also more complex faults can be reduced to a smaller range. 2. Measuring voltage method

　The voltage measurement method is to measure the voltage value and current value of each point according to the power supply mode of the electrical appliance and compare with the normal value. Specifically, it can be divided into step measurement method, segment measurement method and spot measurement method.

3. Resistance measurement method

　It can be divided into step measurement method and subsection measurement method. These two methods are suitable for electrical equipment with large distances between switches and electrical appliances.

5. Comparison, replacement of components, stepwise open circuit (or access) method

(1) Contrast method: compare the test data with the drawings and the normal parameters recorded at ordinary times to judge the fault. For electrical appliances that have no information and no usual records, it can be compared with intact electrical appliances of the same model.　

When the electrical components in the circuit belong to the same control property or multiple components control the same device together, you can use other similar or the same power components to determine the fault.　

(2) The method of placing switching components: when the cause of some circuit failures is difficult to determine or the inspection time is too long, but in order to ensure the utilization of electrical equipment, the experiment of components with good performance in the same phase can be converted to verify whether the fault is caused by the electrical equipment. cause. It should be noted when using the conversion element method to check that after removing the original electrical appliance, carefully check whether it has been damaged. Only when the damage is definitely caused by the electrical appliance itself, can it be replaced with a new appliance to avoid damage to the new component.

(3) Gradually open circuit (or access) method: When multiple branches are connected in parallel and a more complicated control circuit is short-circuited or grounded, there are generally obvious external manifestations, such as smoke and sparks. When the inside of the motor or the circuit with a shield is short-circuited or grounded, it is not easy to find other external phenomena except for the fuse. This situation can be checked by the gradual opening (or access) method.　

(4) Step-by-step open circuit method: In case of a short circuit or ground fault that is difficult to check, the melt can be replaced again, and the multi-branch cross-linking circuit can be disconnected from the circuit step by step or focus all the way, and then energized test, if the fuse Repeatedly blown, the fault lies in the circuit just disconnected. Then divide this branch into several sections and connect to the circuit section by section. When a certain section of the circuit is connected, the fuse blows again, and the fault lies in this section of the circuit and an electrical component. This method is simple, but it is easy to completely burn the electrical components that are not seriously damaged.

(5) Step-by-step connection method: When a short circuit or a ground fault occurs in the circuit, replace the new fuse and gradually or focus on connecting each branch to the power source one by one, and retest. When it is connected to a certain section, the fuse blows again, and the fault lies in the circuit just connected and the electrical components it contains.

5. Forced closing method

When queuing electrical faults, after visual inspection, the fault point is not found and the hand does not have a proper instrument to measure. An insulating rod can be used to forcefully press the relevant relay, contactor, electromagnet, etc. with external force to make the normally open contact. Close, and then observe various phenomena that occur in the electrical or mechanical parts, such as the motor never turning to rotation, and the corresponding part of the equipment from stationary to normal operation.

The faults of equipment circuits or electrical appliances can be roughly classified into six categories: short-circuit, overload, open circuit, grounding, wiring errors, electromagnetic and mechanical part faults of electrical appliances. Most of the faults are open circuit faults. It includes wire disconnection, virtual connection, looseness, poor contact, virtual welding, false welding, fuse blown, etc. In addition to using the resistance method and voltage method to check this type of fault, there is a simpler and more reliable method, which is the short-circuit method. The method is to use a well-insulated wire to short-circuit the suspected open circuit. If it is short-circuited to a certain place, the circuit works back to normal, indicating that the place is open.

6. Short circuit

The specific operation can be divided into partial short connection method and long short connection method.

7. The above several inspection methods should be learned and applied flexibly, and the safety operation regulations should be observed. For components that are continuously burned out, the cause should be found out before replacement; the voltage drop of the wire should be considered when measuring the voltage; the principle of equipment electrical control should not be violated, and the hand should not leave the power switch during the test run, and the insurance should be equal or Slightly smaller than the rated current; pay attention to the selection of the gear of the measuring instrument.