The failures of capacitors | and how can we do with it?

Capacitors are a common electronic component used to store charge and regulate voltage in circuits however, capacitors can also fail, affecting their normal operation.

In this passage, we will explore the reasons for the failure of capacitors, and analyze each reason in detail.

Content：

1、The reasons for the failure of capacitors?

2、Then how we check check and test whether the capacitor is good, defective, open, dead or shorted?

3、What should we do after the capacitor burns out?

The reasons for the failure of capacitors?

1, the capacitor itself product quality problems, such as manufacturing process, materials are not qualified, the capacity of the standard does not match the actual capacity, the use of a long time leading to aging, etc. will cause burnout;

2, the peripheral environment, such as installed in the heat dissipation is not good place or near the heat source, capacitor wiring is not good, poor contact, etc. is also easy to cause burnout;

3, harmonic problems, harmonics make the filter capacitor resonance, resulting in capacitor overcurrent, burn out;

4, too low voltage; centrifugal switch sticking;

5, overload; low speed repeatedly start; or start time is long, etc., to analyze and judge the site of capacitor burnout;

To summarize, the main reasons for capacitor failure include dielectric aging, electrolyte drying temperature changes, voltage exceeds the rated value, mechanical damage and long time unused. In order to extend the service life of capacitors, we need to pay attention to avoid failure due to these reasons. Choosing the right capacitor, using and maintaining the capacitor correctly is the key to ensure that the capacitor works properly.

How we check check and test whether the capacitor is good, defective, open, dead or shorted?

I. Using digital multimeter test capacitors - resistance mode

To test capacitors in resistance "Ω" or ohm mode by DMM (digital multimeter), follow the steps below:

1, Make sure the capacitor is completely discharged.

2、Set the meter on the ohm range (at least set to 1000 ohms = 1kΩ).

3、Connect the multimeter probe to the capacitance terminals (negative to negative and positive to positive).

4. The digital multimeter will display the value.

5, then it will immediately return to OL (open line) or infinity "∞".

If each attempt in step 2 will show the same result as shown in steps 4 and 5, this means the capacitor is good, if not, then the capacitor is bad.

II.Testing Capacitance with a Digital Multimeter - Resistance Mode

Checking Capacitance with an Analog Multimeter - Ohm Mode

To check capacitance by AVO (Ampere, Volt, Ohm Meter) in resistance "Ω" or ohm mode, please follow the steps below.

1. Make sure the suspect capacitor is fully discharged.

2.Take an AVO meter.

3, Turn the knob on the analog meter to select resistance "OHM" mode (always select the higher ohm range).

4. Connect the multimeter leads to the capacitor terminals. (COM connected to "-Ve", positive connected to "+Ve") terminal).

5, Note the readings and compare them with the following results.

SHORT CAPACITANCE: A shorted capacitor will show very low resistance.

Open Capacitance: An open capacitor will not show any movement (deflection) on the ohmmeter scale.

GOOD CAPACITANCE: Initially it will show low resistance and then gradually increase to infinity. This means the capacitor is in good condition.

III. Checking Capacitance Using a Multimeter in Capacitance Mode

Note: Capacitance can be tested in capacitance mode only if the analog or digital multimeter has a Farad "C" function for capacitance. The capacitance mode function of the multimeter can also be used to test tiny capacitances. To do this, turn the knob of the multimeter to capacitance mode and follow the basic instructions below.

1. Make sure the capacitor is completely discharged.

2, Remove the capacitor from the circuit board.

3, Now select capacitor "C" on the multimeter.

4, Now connect the capacitor terminals to the multimeter leads. (Red to positive and black to negative).

5, If the reading is close to the actual value of the capacitor (i.e. the value printed on the capacitor container box).

6, then the capacitor is in good condition. (Note that the reading may be less than the actual value of the capacitor (the rating of the capacitor due to the tolerance in ±10 or ±20).

If you read a significantly lower capacitance value or none at all, the capacitor is depleted and you should replace it with a new one to ensure proper operation.

What should we do after the capacitor burns out?

1, due to the two poles of the capacitor has a residual charge characteristics, so, first of all, should try to discharge its charge, otherwise it is easy to electrocution;

2, dealing with faulty capacitors, first of all should pull the capacitor bank circuit breaker and its upper and lower isolation switches, such as the use of fuse protection, should first remove the fuse tube;

3, although the capacitor bank has been discharged by the discharge resistor itself, but there will still be part of the residual charge, therefore, must be discharged artificially. When discharging, the grounding end of the grounding wire and the grounding network should be fixed, and then use the grounding rod to discharge the capacitor several times, until there is no spark and discharge sound, and finally the grounding wire is fixed;

4, it should also be noted that the capacitor, if there is an internal broken wire, fuse blown or lead contact is poor, there may also be a residual charge between its two poles, and in the automatic discharge or artificial discharge, these residual charges will not be discharged;

5. Therefore, before contacting the faulty capacitor, the operation or maintenance personnel should also wear insulated gloves and short the poles of the faulty capacitor with a short circuit wire in order to discharge it. In addition, the use of series wiring of capacitors should also be discharged separately.