I. Faults with obvious changes in the appearance of the equipment
To troubleshoot this type of fault, we can observe, inquire, smell, listen, and touch to observe external signs and analyze the cause of the fault. In some cases, test driving can also be used to analyze and determine the cause of the fault.
1. Look
Upon arrival at the scene, first observe the environment. If there are significant safety hazards, the power should be cut off immediately. This includes checking for severe burning, overheating, broken wires, and loose wire connection bolts.
2. Question
This involves asking relevant personnel on-site about the phenomena observed when the fault occurred (whether there was smoke, fire, or noise), and inquiring about the intensity of the sound, light, and fire. It's also important to ask if this type of fault is frequent or if it's the first time it's happened. Furthermore, inquire whether anyone has addressed the fault, how it was handled, and whether the equipment returned to normal operation afterward. This process helps in determining the location of the fault and analyzing its cause based on the operating principles of the electrical equipment.
3. Smell
Use your nose to smell for any burning odor. Carefully sniff around the general area where the fault occurred. Often, you can find the fault by smelling the electrical equipment and wiring.
4. Listen
Electrical equipment and components such as motors and transformers produce different sounds when operating normally compared to when they malfunction. Listening to these differences can help us quickly locate the fault. This is especially important for motors; we need to listen carefully to their operating sounds.
5. Touch
Touching involves disconnecting the power supply to the equipment and lines, and then manually touching the faulty equipment and lines to check if the equipment temperature and temperature rise are normal. For motors and transformers, check for localized overheating; if so, it's usually due to a short circuit between coil turns. Touching can often quickly pinpoint the fault .
6. Test run
After a preliminary inspection confirms that the fault will not escalate further or cause personal injury or equipment damage, a test run can be conducted. During the test run, start it briefly, then immediately stop. Only after confirming there are no major issues should you attempt to start it a second time. During the second test run, pay attention to any severe sparking, unusual odors, or abnormal sounds. If any of these phenomena are observed, stop the machine immediately and disconnect the power. Then, investigate the cause, carefully checking the temperature rise of the electrical components and whether their operating procedures conform to the requirements of the electrical equipment schematic diagram to locate the fault.
II. Faults where there are no obvious changes to the equipment's appearance.
These types of faults are mainly caused by malfunctions, poor contact, or open circuits in various relays, buttons, limit switches, etc. When encountering such faults, it is necessary to use instruments and meters, along with one's own experience, to quickly locate the fault point and cause. The steps and methods for troubleshooting are as follows:
1. Measurement method: measuring voltage, current, and resistance .
1 ) Measure voltage and current.
It involves measuring the voltage and current values at corresponding points based on the power supply method and voltage of electrical equipment and lines. The measured voltage and current values are then compared with normal values to analyze and determine the cause of the electrical equipment malfunction.
2 ) Measure resistance.
Research the normal resistance values of electrical equipment, then measure the resistance and compare it with the normal value to determine the continuity of the equipment and the cause of the fault. The advantage of resistance measurement is safety; however, its disadvantage is that inaccurate measurements can easily lead to incorrect judgments. Always disconnect the power supply when measuring resistance. If the circuit is connected in parallel with other circuits, it must be disconnected from them; otherwise, the measured resistance value will be inaccurate, leading to incorrect judgments.
2. Component replacement method and step-by-step open circuit method
1 ) Method of setting conversion element:
If the cause of a circuit failure can be preliminarily identified as being caused by a certain component, it can be replaced with a high-performance component, provided that safety is ensured, to determine whether the failure was caused by the damage to that component.
2 ) Opening the path method:
When an electrical circuit experiences a short circuit or grounding, there are usually obvious signs of smoke, sparks, and burning. Visual inspection can often resolve the issue. For difficult-to-detect short circuits or grounding faults, multiple parallel circuits can be disconnected one branch at a time, and then measured individually to determine the cause. It is recommended to use instruments for inspection. I believe that using the current-through method is not advisable, as the powerful short-circuit current can easily burn out components and equipment if the electrical equipment and wiring are already faulty.
3. Short - circuit method
Among electrical equipment and wiring faults, open circuit faults are the most common. These include broken wires, poor contact, loose connections, cold solder joints, false solder joints, and blown fuses. Besides using resistance and voltage methods to check for these faults, there is a simpler and more reliable method: the short-circuit method. This involves using a well-insulated wire to short-circuit the suspected open circuit. If the circuit returns to normal operation after shorting to a certain point, it indicates that the circuit was open at that location.
This method can quickly locate faults, and many electricians prefer to use it. However, it is crucial to be extremely careful not to short-circuit incorrectly. For example, short-circuiting high-voltage and low-voltage circuits, or short-circuiting between phases. Incorrect short-circuiting can cause short circuits or malfunctions, expanding the fault area or causing serious consequences. During maintenance, short-circuiting is strictly prohibited for equipment and lines carrying high currents. Short-circuiting high-current equipment or lines with wires will generate powerful arcs, which can harm equipment and personnel.
In addition, many electrical maintenance personnel like to use the forced closure method to find faults during troubleshooting, and this method is also feasible. However, like the short-circuit method, this method should not be used when encountering equipment and lines with strong or high current.
4. Current method
In fact, using a clamp meter to check for faults is a very good method for electrical equipment maintenance personnel when inspecting electrical equipment and wiring. When electrical equipment malfunctions, the current will change. Observing the current with an ammeter can quickly determine the fault. For example, if the three-phase current of a motor is too high, it is an overload; if the three phases are unbalanced, it may be a short circuit between turns in the motor windings. When the electrical equipment itself has a fault, but it is necessary to power it on to find the cause of the fault, the power-on time should not be too long. For example, if a three-phase motor is running with one phase missing, prolonged power-on time will burn out the motor.
III. Summary
The above are all methods for troubleshooting when electrical equipment or electrical circuits malfunction.
Sometimes, when equipment malfunctions, the electrical wiring and equipment themselves are not faulty; rather, the problem lies in the mechanical linkages. Therefore, when troubleshooting electrical equipment, we should not neglect to inspect the mechanical components. Faults in the mechanical parts must be investigated, adjusted, and repaired. Only when the mechanical components are functioning properly can the electrical equipment operate normally.
The steps and methods for inspecting and analyzing electrical equipment should be flexibly applied according to different fault conditions. This is the only way to quickly and effectively locate the fault point, determine the cause of the fault, and eliminate the fault in a timely manner.
