As a maintenance electrician, in the event of electrical faults, can accurately identify the cause of the fault, reasonable and correct troubleshooting, to improve labor productivity, reduce economic losses and safe production are of great significance. Electrical equipment fault checking basic ideas are as follows:
1. Intuitive method intuitive method is based on the external performance of electrical faults, through the means of seeing, smelling, listening, etc., checking, determining the fault method.
(1) check the steps: investigate the situation: to the operator and the failure of the personnel present to ask about the situation, including the failure of the external performance, the general part, the occurrence of the failure of the environmental conditions. Such as the presence of abnormal gas, open flame, heat source is close to the electrical appliances, corrosive gas intrusion, water leakage, whether someone repaired, the content of the repair and so on. Preliminary inspection: according to the investigation, to see the relevant electrical external damage, connecting line has no broken, loose, insulation has no burnt, spiral fuse fuse indicator is jumped out, electrical water, grease and dirt, switch position is correct and so on. Trial: through the initial inspection, confirm that there will be further expansion of the fault and cause personal and equipment accidents, can be further test drive inspection, test drive to focus on whether there is a serious jumping fire, abnormal odor, abnormal sound and other phenomena, once found should be immediately stopped, cut off the power supply. Focus on checking the temperature rise of electrical appliances and electrical action procedures in line with the requirements of the schematic diagram of the electrical equipment, so as to find the fault parts.
(2) inspection method: observation of sparks: electrical contacts in the closing, breaking the circuit or wire threads loose will produce sparks, so you can check the electrical failure according to the presence or absence of sparks, size and other phenomena. For example, the normal tightening of the wire and screws found between the spark, indicating that the wire is loose or poor contact. Electrical contacts in the closing, breaking the circuit when the fire jumping indicates that the circuit passes, does not jump the fire indicates that the circuit does not work. Control motor contactor main contact two-phase sparks, a phase without sparks, indicating that no spark of a phase contact poor contact or this phase of the circuit breaks; three-phase two-phase sparks than normal, don't one compared to the normal small, can be initially determined as a short circuit between the phases of the motor or ground; three-phase sparks than normal, may be the motor is overloaded or the mechanical part of the jam.
In the auxiliary circuit, the contactor coil circuit is energized, the armature does not suction, to distinguish between circuit breaks or contactor mechanical part of the card caused. Can press the start button, such as the button normally open contacts closed position when disconnected with a slight spark, indicating that the circuit is open, the fault is in the contactor's. mechanical part; such as contacts closed position when disconnected with a slight spark, indicating that the circuit is open, the fault is in the contactor. Mechanical part; such as no spark between the contacts, indicating that the circuit is broken. Action program: the action program of electrical appliances should be in line with the requirements of the electrical instructions and drawings. If the action of the appliance on a circuit is too early, too late or no action, it means that the circuit or appliance is faulty. In addition, you can analyze and determine the fault based on the sound, temperature, pressure, smell, etc. emitted by the appliance. The use of intuitive method, not only can determine simple faults, but also more complex faults can be narrowed down to a smaller range.
2. Measurement of voltage method of measurement of voltage method is based on the power supply mode of the appliance, measuring the voltage value and current value of each point and compare it with the normal value. Specifically, it can be divided into step-by-step measurement method, segmentation measurement method and point measurement method.
3. Measurement of resistance method can be divided into step-by-step measurement method and segmented measurement method. These two methods are suitable for switches, electrical appliances distributed over a large distance of electrical equipment.
4. Comparison, replacement of components, step-by-step open circuit (or access) method
(1) Comparison method: the detection of data and drawings of information and usual records of normal parameters compared to determine the fault. No information and no usual record of appliances, can be compared with the same type of intact appliances. Circuit electrical components belonging to the same control properties or multiple components *** with the control of the same equipment, you can use other similar or the same power supply components action to determine the fault.
(2) set the conversion component method: the cause of failure of some circuits is not easy to determine or check the time is too long, but in order to ensure that the utilization of electrical equipment, can be converted to the same phase of the performance of the components of the experiment to confirm the failure of the appliance caused by this. The use of conversion components method should focus on checking, when the original appliances removed, to carefully check whether it has been damaged, only certainly due to the damage caused by the appliance itself factors, in order to replace the new appliances, so as to avoid damage to the new replacement components again.
(3) step by step open circuit (or access) method: multi-branch parallel and more complex control of the circuit short circuit or grounding, there are generally obvious external manifestations, such as smoke, sparks and so on. Inside the motor or with a shrouded circuit short-circuit, grounding, in addition to the fuse blown, it is not easy to find other external phenomena. This situation can be used to gradually open the circuit (or access) method of inspection. Step-by-step open method: encountered difficult to check the short-circuit or grounding fault, you can re-replace the fuse, the multi-branch crosslinked circuit, all the way all the way step by step or focus from the circuit breaks open, and then energized to test, if the fuse again and again melted, the fault is in the just disconnected on this circuit. Then the branch circuit is divided into several sections, section by section to access the circuit. When access to a section of the circuit when the fuse is blown, the fault is in this circuit and an electrical component. This method is simple, but easy to damage not serious electrical components completely burned. Gradual access method: the circuit appears short-circuit or ground fault, replace the new fuse gradually or focus on the branch circuit one by one access to the power supply, retest. When a section of the fuse and fuse, the fault is just access to the circuit and the electrical components contained in this.
5. Forced closure of the law in the queue of electrical faults, after visual inspection did not find the fault point and there is no appropriate instrumentation under the hands of the measurement, can be used as an insulated rod will be related to the relay, contactor, solenoid, etc. with an external force forced to press, so that its normally open contacts closed, and then observe the electrical part of the mechanical part of the phenomena such as motors from not to turn to rotate the corresponding parts of the equipment From immobility to normal operation, etc.
6. Short connection method equipment circuit or electrical faults are roughly summarized as short-circuit, overload, disconnection, grounding, wiring errors, electrical electromagnetic and mechanical part of the failure and other six categories. ;