Dosage of electrolytic capacitor
in the electrical equipment is very big, very high failure rate.
Damage of electrolytic capacitor has the following kinds: one is completely out of smaller capacity or capacity;
The second is mild or severe leakage;
3 it is both the leakage loss of volume or capacity smaller.
Refers to the aluminum electrolytic capacitor, tantalum, niobium, titanium metal surface anodic oxidation method is used to generate a thin layer of oxide as the dielectric, composed of capacitor in electrolyte as the cathode.
Electrolytic capacitor leakage resistance measurement method and the process steps and attention items.
Leakage current is three main performance index of the electrolytic capacitor (
Electric capacity, loss tangent value and leakage current)
One of leakage through the assembly of capacitance in circuit directly influence such as filtering, dc insulation effect, but in the use of large capacity electrolytic capacitor timing circuit for a long time, the index greater influence on the timing precision of circuit.
Before production to demand higher circuit, therefore, it is necessary to test the first important indicators.
Find the damaged electrolytic method: (
See: some capacitance damage when leakage, capacitance below the surface of the circuit board and even appearance is a layer of oily be soiled, absolutely can't use the capacitance;
Some damage will summon the capacitance and the capacitance can't continue to use;
Touch: boot after some leakage serious electrolytic capacitor will be fever, when a finger touch even hot, this kind of capacitor must be replaced.
Electrolytic capacitor with electrolyte, bake for a long time can make electrolyte dry, cause the capacitance is reduced, so the key to check the radiator and nearby capacitance, high power components as close to it, the greater the likelihood of damage.
Electrolytic capacitor damage usually have the following reasons: 1, rectifier tube damage when one of the rectifier bridge rectifier is breakdown, the rectifier voltage will appear after the communication component, reverse voltage appears on the filter capacitor, filter capacitor and damage.
2, uneven distribution of the voltage when one of the equalizing resistance damage, each series capacitor on the voltage distribution of the two groups have become unbalanced, the high voltage capacitor is easy to damage.
3, capacitor leakage current is too large electrolytic capacitor access circuit, is the existence of leakage current.
Under normal circumstances, the leakage current is very small.
But if the capacitor aging, or due to the quality of the capacitor itself was lacking reason, leakage current will increase, make the electrolytic capacitor will be damaged due to severe fever.
Electrolytic capacitor leakage resistance measurement methods: when the multimeter is used to inspect the size of the electrolytic capacitor leakage current, multimeter red pens and electrolytic capacitor anode, black pens and the anode, just contact moment, multimeter pointer deflection to the right was substantial (
For the same -
Electric block, the bigger the capacity, the greater the swing)
, then gradually turning to the left until the stop at a particular location, the resistance value is positive leakage resistance of electrolytic capacitors, this value is, the greater the leakage current is smaller, the better the performance of capacitance.
Then, the switch will be red and black pens and detection.
Multimeter pointer will repeat the swing, but at the moment, the measured resistance reverse leakage resistance for electrolytic capacitor, this value is slightly smaller than the leakage resistance, namely the reverse leakage current is bigger than positive leakage current.
Practical experience shows that the leakage resistance of the electrolytic capacitor shall generally be in the hundreds of thousands of the above, otherwise can't work normally.
In testing, if both forward and reverse phenomenon without charge, that pointer, capacitance disappear or internal circuit;
If the resistance is small or zero, the capacitor leakage or have broken down, cannot use.
Should be paid attention to in the test, choose the appropriate range, in general, 1 ~ 47 uf capacitance available Rx1k Ω block, greater than the Rx 100 available 47 uf Ω block.
When the condenser pressure value is greater than the universal clothing internal battery voltage value, according to the electrolytic capacitor charging forward small leakage current when charging, reverse leakage current is big, the characteristics of using Rx10k Ω block to reverse charge of electrolytic capacitor, whose hands resting place to observe whether stable (
The reverse leakage current is constant)
, the capacitor quality, accuracy is higher.
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