Hi,
I'm using a 1000uF 16V capacitor in my power supply (12V AC rectified). The voltage on the capacitor terminals is 15.5V.
I'd like to know if the 16V parameter of my capacitor is a stress value, or if it's a nominal value meaning that my capacitor is safe with voltages less or equal than that.
If I remember correctly that is the capacitors maximum safe voltage, if exceeded, the capacitor could pop, melt itself, unbond the solder, discharge too much/too little, spike, short, etc. I'd say stay just below the max voltage just to be safe.
Electrolytic capacitors are 'formed' during manufacture by depositing an anodic film on the aluminium foil that makes up the anode, that will withstand the operating voltage plus (typically) 10%.
So you are quite safe to operate them at their specified working voltage.
I have a question along the same lines what about the uF is that just a "safe" working value or would replacing a capacitor with a higher UF be a bad Idea? For exaple I have a 100uF 16V capacitor and was thinking of replacing it with a 150uF 20V.
I did some further research on this and found that in doing repairs, it is not a good idea to change the uF of the capacitors used. So I could go with a 100uF 20V but shouldn't use a 150uF 20V. If anyone has more information on this feel free to say so, as I am just going off what I have read.
Think of it like a resistor. A resistor has a power rating (in wattage) and a resistance rating. You can replace a 300-ohm ¼ watt resistor with a 300-ohm 1-watt resistor. Only difference is that the 1-watt resistor can withstand a higher current/wattage (or heat) level. Having a higher wattage handling capability does not affect the circuit design, other than giving it the ability to handle more heat.
However, if you change the resistance value, then you change the current level across the resistor and across the circuit. That will definitely affect the circuit.
(In this example, uF rating is equivalent to resistance and wattage is equivalent to voltage – Just an analogy to try to put it in perspective :wink: )
I did some further research on this and found that in doing repairs, it is not a good idea to change the uF of the capacitors used. So I could go with a 100uF 20V but shouldn't use a 150uF 20V. If anyone has more information on this feel free to say so, as I am just going off what I have read.
You may need to replace an electrolytic which is part of a CR time constant in some timing circuit. If so, don't change the value, or you will upset the timing.
Other than that, electrolytics are used as reservoir or smoothing and you can usually safely exceed the capacity specified. The only time I would add a word of caution is if the capacitor is very large, say, several thousand uF and is used as reservoir straight after a recifier and with no series resistor to limit surges. In that case the rectifier could possibly be damaged by the surge current.
As I said before, eleectroytics should be used within their rated (as marked) voltage. Straight after a rectifier the voltage can increase to 1.4 x the applied AC, so it is a point to watch.