Capacitor run what are often prone to abnormal situation?
Compensation capacitor is often prone to run the belly drum shell, casing or a leak from the tank. The main reason is due to high temperature capacitors. The temperature is too high by the following factors. 1, ambient temperature is too high, ventilation.
2, power supply voltage exceeds rated value, causing overload fever.
Capacitor detection methods and replacement
Capacitor common form of marking is a direct marker of its common units pF, μF two kinds, it is easy to recognize. However, some small capacity of the capacitor used in digital labeling law, generally there are three digits, the first and second digit as a valid number, the third multiple of the median, it means that the number of 0 behind Yao Gen. For example: 343, said 34000pF, In addition, if the third digit is 9, indicating 10-1, instead of 10 9-th power, for example: 479, said 4.7pF.
Replacement of capacitor, the main capacitor voltage should be noted that the general requirements of not less than the original value of the capacitance voltage requirements. In the call for more stringent circuit, its capacity is generally not more than ± 20% of the original volume can be. In the circuit with less stringent requirements, such as the bypass circuit, generally require no less than the original capacitor 1 / 2 and not more than 2 times the original capacitance can be ~ 6 times.
1 Detection of the fixed capacitor
A detect the small capacitance below 10pF due to the following fixed 10pF capacitor capacity is too small to measure with the multimeter, only a qualitative check whether there is leakage, the internal short circuit or breakdown phenomenon. Measurements, it can use multimeter R × 10k block, with two tables T 2 respectively, the capacitance of arbitrary access pin, resistance should be infinite. If the measured resistance value (a pointer to the right swing) is zero, then capacitor leakage damage or internal breakdown.
B detection 10PF ~ 1000μF whether there is a fixed capacitor charging phenomenon, and then judge its good or bad. Multimeter selected R × 1k block. 2 transistor β values are above 100, and through current can choose to have some other type of silicon transistor formed 3DG6 composite pipe. Multimeter's red and black table pen and composite pipe, respectively e emitter and collector c-phase. As the composite transistor amplification, the process of charging and discharging capacitor under test to be larger, so that the pointer of swing meter increase, and thus easy to observe. It should be noted: In the test operation, especially in the smaller capacity of the capacitance measured when the measured capacitance pin to repeatedly swap contacts A, B two points, in order to clearly see the multimeter pointer swing.
C fixed for more than 1000μF capacitor, available multimeter R × 10k block directly test whether the process of charging capacitor, as well as whether the internal short circuit or leakage, and can swing to the right under the pointer to estimate the magnitude of the size of capacitor capacity.
2 electrolytic capacitor testing
A because the capacity of electrolytic capacitors is much greater than the average fixed capacitor, therefore, measurements should be the appropriate choice of different capacities range. Based on experience, under normal circumstances, 1 ~ 47μF capacitance between that can be used R × 1k block measurements, is larger than 47μF of capacitance measurements can be used R × 100 block.
Table B the multimeter red pen then negative, then positive black table pen, in the new to the moment, multimeter pointer that the deflection of a larger skewness to the right (for the same power to block the capacity the greater the greater the swing), and then gradually to the left turn, until the stop at a certain location. At this point the resistance is positive electrolytic capacitor leakage resistance, this value is slightly larger than the reverse leakage resistance. Actual experience shows that the leakage resistance of electrolytic capacitors should normally be a few hundred kΩ or more, otherwise, it will not work properly. In the test, if positive, no charge reverse phenomenon, namely,表针not move, then lost the capacity or the internal circuit; if the measured resistance of very small or zero, indicating large capacitor leakage or breakdown damaged, can not be used again.
C for the positive and negative signs of unknown electrolytic capacitors can be measured using the above method to determine leakage resistance. Which is to look at any measure leakage resistance, remember its size, and then swap the table T and then measured by a resistance. Two measurements of resistance and that one is a big positive then the law, that the black pen then the table is positive, the red pen then the table is the negative.
D power to block the use of multimeter, using electrolytic capacitors to be positive, the reverse charge method, according to the size of a pointer to the right swings can estimate a capacity of electrolytic capacitors.
3 detection of variable capacitor
A hand gently rotating shaft, should feel very smooth and should not feel tight and sometimes lax, and even catching the phenomenon. Will contain the axial front, back, up, down, left and right in various directions and promotion, the shaft should not be loose phenomenon.
B rotating shaft with one hand, the other hand light-touch move the outer edge of the film group should not feel any loose phenomenon. Poor contact between the shaft and the moving film of the variable capacitor, can not continue to use.
C will be placed in R × 10k block multimeter, a pen in hand the two tables were then fixed variable capacitor chips and fixed film leads to side, the other hand to slowly rotating shaft a few back and forth, multimeter pointer are infinite position should be fixed. In the rotating shaft of the process, if the pointer is sometimes point to zero, indicating movement between the film and the stator short-circuit point; If you hit a certain point of view, multimeter reading is not infinite, but many will certainly resistance, indicating a variable capacitor move exists between the film and the stator leakage phenomenon.
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