Should I really use a higher voltage capacitor?

[erwin1978]

I read that I can replace a capacitor with the same capacity and equal or greater voltage. Would it be wiser to use a capacitor with the same voltage as the original? My concern is if I use a capacitor with a higher voltage tolerance then it could also pass the higher voltage further down the circuit and cause more damage. Instead of a cheap capacitor sacrificing itself now other components could die as well. Am I justified to think this?

 

[Leros]

I wouldn't worry about it.

Capacitors are generally placed in parallel with other paths in the circuit. A high voltage would probably get through the board one way or the other. Not to mention, if a higher voltage has reached the capacitor, its likely in other places on the board. Its also likely that max voltage of the original capacitor was high enough to pass some pretty damaging voltages.

 

[Mark R]

Capacitors offer no useful protection against over-voltage; they can withstand overvoltage for a long time (the effect is to shorten the caps life, unless the overvoltage is extreme).

Higher voltage caps tend to have slightly higher performance for otherwise equivalent specs - however, they are bigger and more expensive. However, dont't just assum that a high voltage cap has the required performance - if the cap is for a specific job, it must be a model that is designed for it.

 

[bobsmith1492]

Depending on the type of capacitor, it may or may not fail "sacrificing itself" in lieu of other components.

Ceramic capacitors will tolerate double their rated voltage for some amount of time without any problems. Electrolytics, on the other hand, will begin to draw current at a fairly low amount of overvoltage, acting to clamp the voltage. So in rare cases you may be right, but if the design is relying on electrolytics to clamp voltage spikes then it's a poor design to start and probably won't last long no matter what you do!

However, without knowing the circuit and its purpose, the only safe option is to use the same part number component as a replacement. For example, in a switching power supply, the filter capacitor must have a specific amount of ESR; in some designs, too little ESR will cause the supply to become unstable, while in all designs too much ESR will result in higher voltage ripple.

 

[Colt45]

The only thing a higher-voltage-than-required cap does is waste money.

 

[PowerEngineer]

What really counts is the value of the capacitance (and whether or not it's electrolytic for polarity). The voltage rating on a capacitor is much like the wattage rating on a resistor. You want one with a rating that meets or exceeds what it will be exposed to in your application. The fact that it has a higher rating has no effect on the way it functions in your circuit. As mentioned above, the best idea is to replace it with the same part number; otherwise, waste a little money on one with the same construction and the higher voltage rating.

 

[Rubycon]

Ok higher never lower. Think of it as the power rating of a resistor. The WVR of a capacitor chiefly is determined by its breakdown strength. If you frequently exceed this then it will fail sooner. Also some caps are (i.e. Tantalum) are not resistant to reversal - at all!

 

[erwin1978]

I also read too high a voltage is bad because of ripples.

 

[PottedMeat]

I also read too high a voltage is bad because of ripples.

ripple is caused by insufficient capacitance or high esr, not rated working voltage. the rated voltage tells you the highest voltage that particular capacitors' dielectric can tolerate before it breaks down.