First, the appearance of the equipment has obvious changes of the fault
To find this kind of fault, we can look, ask, smell, listen and touch to get some appearance, through the appearance of the phenomenon to analyze the cause of the fault. In some cases, it can also be analyzed through a test run to get the cause of the failure.
1,"
After arriving at the site, observe the environment first, and cut off the power supply when there is a major potential safety hazard. Look, is to see if there is serious burn, heat, broken wire, wire connection bolts are loose, etc.
2, q
Is to the scene of the relevant personnel to ask what happens when the fault (there is no smoke, there is no fire, there is no sound), ask the size of the sound, light, fire. Also ask if this failure is a regular occurrence or a first. After the fault occurs, whether the personnel have dealt with it, how to deal with it, and whether the operation is normal after processing. In this way, it is helpful to judge the fault location and analyze the cause of the fault according to the working principle of the electrical equipment.
3, smell
Smell with your nose, see whether there is a smell of coke, smell the approximate location of the fault carefully, through the smell of electrical equipment and electrical lines, often can find the point of failure.
4, listen to the
Electric motors, transformers and other electrical equipment and components, in the normal operation of the sound and failure of the sound is different. By listening, you can quickly find the fault. Especially for electric motors, we should listen carefully to the sound of its operation.
5, touch
Touch is to disconnect the power supply of the device and the line, and touch the faulty device and the line by hand to check whether the temperature of the device is normal and whether the temperature rise of the device is normal. Motor and transformer, to see whether local heating, if local heating, generally is its coil turns short circuit. Through touch, often can quickly find the fault point.
6, commissioning
After the preliminary inspection is confirmed that the fault will not further expand and cause personal and equipment accidents, the test run inspection can be carried out. Test run, first move, immediately stop, confirm no serious injury, only the second start. In the second test, pay attention to whether there is serious fire jumping, abnormal smell, abnormal sound and other phenomena, once found one of the above phenomena, should immediately stop and cut off the power supply. Then find the cause, pay attention to check the temperature rise of electrical appliances and electrical action program is in line with the requirements of electrical equipment schematic diagram, so as to find the fault location.
Two, the appearance of the equipment without obvious change of the fault
This kind of fault is mainly caused by the failure of various relays, or buttons, or travel switches, or poor contact, or open wires and so on. Encounter this kind of failure, it is necessary to use instruments, coupled with their own experience, to quickly find out the point of failure and the cause of failure. The search steps and methods are as follows:
1, measurement method: measure voltage, current and resistance
1) Measure voltage and current.
The voltage and current value of the corresponding point are measured according to the power supply mode and voltage of the electrical equipment and line. The measured voltage value and current value are compared with the normal value, so as to analyze and judge the cause of electrical equipment failure.
2) Measuring resistance.
Find out the information, make clear the normal resistance of electrical equipment, and then measure the resistance, the measured resistance and the normal value of the comparison, so as to judge the electrical equipment on and off, the cause of failure. The advantage of resistance measurement is safety, but the disadvantage is that it is easy to make mistakes when the resistance value is not accurate. When measuring resistance, disconnect the power supply. If the circuit is connected to another circuit in parallel, disconnect the circuit from another circuit. Otherwise, the measured resistance value will be inaccurate, resulting in incorrect judgment.
2, displacement element method, gradually open circuit method
1) Conversion element method:
When the fault cause of some circuit can be preliminarily identified as caused by a component, it can be replaced with a component with good performance under the condition of ensuring safety, so as to judge whether the fault is caused by the damage of the component.
2) Open circuit method:
When the electrical circuit is short-circuited or grounded, there are obvious smoke, sparks and scorch marks. It can often be ruled out by observation. In case of short circuit or grounding fault that is difficult to check, the multi-branch parallel circuit can be interrupted one by one from the line, and then judged by measuring one by one. When checking, it is recommended to use instruments to check. I think it is not good to use the electrification method to check, because the electrical equipment and circuit itself have broken down, strong short-circuit current is easy to burn the components and equipment.
3, short connection method
Among the faults of electrical equipment and circuit, there are often more circuit breakers. Such as wire break, poor contact, loose, virtual welding, fake welding, fuse fuse, etc. For this kind of fault in addition to the resistance method, voltage method inspection, there is a more simple and reliable method, is the short connection method. Its method is, with a good insulation of the wire, will be suspected of short circuit part of the connection, such as short received somewhere, circuit work to restore normal, indicating that the connection.
This method can quickly find the fault, many electricians like to do. But note: in the short connection, do not pay attention to short error. Such as high and low voltage short-circuit, phase and phase short-circuit. If the short connection is wrong, there may be short circuit or misoperation, but expand the scope of the fault, or cause serious consequences. In maintenance, for strong current, large current equipment and lines, is not allowed to use short-circuit troubleshooting. Short-circuited wires with strong current or high current will pull up a strong arc light, which will cause damage to equipment and personnel.
In addition, in maintenance, many electrical maintenance personnel like to use forced closure to find faults, this method is also feasible. However, as with the short connection method, it is not suitable to use this method when encountering equipment and lines with strong current or high current.
4. Current method
In fact, electrical equipment maintenance personnel in the maintenance of electrical equipment and lines, if the use of clamp ammeter to check the fault, is also a very good way. When electrical equipment fails, the current will change. Using an ammeter to observe the current can also quickly determine the fault. If the motor three phase current is too large, that is overload; Such as three-phase imbalance, may be the motor windings between the short circuit problem. When the electrical equipment itself is faulty but needs to be powered on to find the cause of the fault, the power on time should not be too long. For example, the three-phase motor is short of phase operation. If it is powered on for a long time, it will burn the motor.
Third, summary
The above mentioned, all electrical equipment, electrical circuit itself when the fault of the fault search method.
Sometimes, when the equipment fails, in fact, the electrical circuit and the electrical equipment itself is not faulty, but the mechanical linkage part is faulty. Therefore, when we troubleshoot electrical equipment, do not ignore the inspection of the mechanical part, the failure of the mechanical part to troubleshoot, adjust and repair. Electrical equipment can only work properly if the mechanical equipment is in order.
The steps and methods for checking and analyzing electrical equipment should be flexibly mastered according to different fault situations. In this way, the fault can be quickly and effectively found and the cause of the fault determined for timely troubleshooting.