1. Talk first, then do it

Guizhou electrical equipment talked about the electrical equipment with fault, should not rush to start, should first inquire about the process and phenomenon of the fault. For unfamiliar equipment, it is also necessary to be familiar with the circuit principle and structural characteristics, and comply with the corresponding rules. Before disassembly, it is necessary to be fully familiar with the function, position, connection mode of each electrical component and its relationship with other devices around it. If there is no assembly drawing, a sketch should be drawn and marked while disassembling.

2. From outside to inside

The equipment should be checked for obvious cracks and defects, and the maintenance history, service life, etc. should be understood, and then the internal inspection should be carried out. Before dismantling, the surrounding fault factors should be queued up, and the disassembly can only be carried out after the internal fault is determined. Otherwise, the equipment may be damaged as the equipment is repaired blindly.

3. Mechanical before electrical

Only after confirming that there is no fault in the mechanical parts, then carry out the electrical inspection. When checking the circuit fault, we should use the detection instrument to find the fault position, and then check the operation relationship between the circuit and the machine after confirming that there is no bad contact fault, so as to avoid misjudgment.

4. First static then dynamic

When the equipment is not powered on, judge the quality of electrical equipment button, contactor, thermal relay and fuse, so as to determine the fault. Power on test, listen to the sound, measure parameters, determine the fault, and finally carry out maintenance. If there is no phase in the motor, if the measurement of the three-phase voltage value can not be distinguished, you should listen to the sound, and measure the voltage of each phase to the ground separately to determine which phase is defective.

5. Clean before repair

For the electrical equipment with heavy pollution, clean the buttons, wiring points and contact points, and check whether the external control key fails. Many faults are caused by dirt and conductive dust. Once cleaned, the faults will be eliminated.

6. Power before equipment

The failure rate of power supply part accounts for a high proportion in the whole fault equipment, so it is often twice the result with half the effort to overhaul the power supply first.

7. Common before extraordinary

The faults caused by the quality of assembly parts or other equipment faults generally account for about 50% of the common faults. Special faults of electrical equipment are mostly soft faults, which should be measured and maintained with experience and instruments.

8. Outside first and then inside

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

9. DC before AC

During maintenance, the static working point of DC circuit must be checked first, and then the dynamic working point of AC circuit.

10. Debug after failure first.

For the electrical equipment with debugging and fault coexisting, the fault should be eliminated first, and then the debugging must be carried out under the premise of the speed of the electric line.

2、 Inspection method and operation practice

1. Intuitive method

Visual method is based on the external performance of electrical fault, through the means of seeing, hearing, listening, etc., to check and determine the fault.

(1) Inspection steps:

Investigation: ask the operator and the fault site personnel about the situation, including the external performance of the fault, the general location, and the environment when the fault occurred. Such as whether there is abnormal gas, open fire, whether the heat source is close to the electrical appliance, whether there is corrosive gas invasion, whether there is water leakage, whether someone has repaired it, and the contents of the repair, etc. Preliminary inspection: according to the investigation, check whether the external parts of the electrical appliances are damaged, whether the connecting wires are open circuited or loose, whether the insulation is burnt, whether the fuse indicator of the spiral fuse jumps out, whether there is water or oil dirt in the electrical appliances, and whether the switch position is correct.

Test run: after the preliminary inspection, it is confirmed that the fault will further expand and cause personal and equipment accidents, further test run inspection can be carried out. During the test run, attention should be paid to whether there is serious ignition, abnormal smell, abnormal sound and other phenomena. Once found, stop the machine immediately and cut off the power supply. Pay attention to check whether the temperature rise of the electrical appliance and the action procedure of the electrical appliance meet the requirements of the schematic diagram of the electrical equipment, so as to find the fault position.

(2) Inspection method:

Observe the spark: when the contact of the electric appliance is closed or broken, or the wire head is loose, the spark will be generated. Therefore, the electrical fault can be checked according to the appearance and size of the spark. For example, when a spark is found between the normally tightened wire and the screw, it indicates that the wire end is loose or has poor contact. When the contact of the electric appliance is closed or disconnected, it means that the circuit is on, and if it is not, the circuit is blocked.

When the two phases of the main contact of the contactor of the control motor have sparks, and one phase has no spark, it indicates that the contact of one phase without spark is poor or the circuit of this phase is open circuit; the sparks of two phases in the three phases are larger than normal, and the other one is smaller than normal, which can be preliminarily judged as short circuit or grounding of motor phase; the sparks of three phases are larger than normal, which may be overload of motor or jamming of mechanical part. 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 open circuit or the mechanical part of the contactor is stuck. You can press the start button once. If there is a slight spark when the normally open contact of the button is disconnected, it indicates the circuit path, and the fault is in the mechanical part of the contactor; if there is no spark between the contacts, the circuit is open circuit.

Action procedure: the action procedure of electrical appliances shall meet the requirements of electrical instructions and drawings. If the electric appliance on a circuit acts too early, too late or does not act, it indicates that the circuit or electrical appliance is faulty. In addition, the sound and pressure of electrical appliances can be analyzed. By using the intuitive method, not only the simple fault can be determined, but also the more complex fault can be reduced to a smaller range.

2. Voltage measurement method

The voltage measurement method is