I want to take suggestion that, Whether I can use electrolytic polarised capacitor for filtering of wave forms of Bridge of power inverter?
At this moment, I am working on filter designing. And I am confused which type of capacitor I use. I need 100uF capacitor. I don't know which technology and type of capacitor I should use.
Please give me suggestions.
I don't know what your circuit does exactly, but the easy way to answer the question is that polarized electrolytic capacitors should only be used if they are not reverse biased. The voltage on the + terminal must always be greater than or equal to the voltage at the - terminal. Otherwise, the capacitor may begin to behave like a short circuit. (You might have a slight amount of leeway for reverse biasing, but I would not count on that!)
If this is okay for your circuit, you're good.
You can also buy non-polarized electrolytic capacitors, but their capacitance values tend to be quite a bit smaller.
http://www.capacitorguide.com/electrolytic-capacitor/
Sir, Thank you for your response.!
Actually, I am using LC filter for power inverter. For cut-off frequency, I have calculated C=100uF and L=65mH. Indeed, output should be 50-60 Hz.
My inverters response is +12 to -12 volts and 650 Hz frequency. And I read that polarized electrolytic capacitors do not work in higher frequencies.
Dear Ghazanfar,
"higher frequencies" is relative. 650Hz should still be very fine with electrolytics.
You can make an own estimate by taking the internal resistance (ESR) of the capacitor and its capacitance to calculate a time constant of the cap. Then you see, if it's fast enough. (e.g. TDK B43630A2397M0*#: 390µF*90mOhm (at 300Hz) = 35µs >> could work up to 10kHz; fast estimate, pls double check)
But really the main issue I see as awell as Mr. Manfredi wrote is the voltage shape:
Elcos only work with DC voltage (= only positive voltage pos-to-neg terminal) - so if you want to use it to filter an AC signal, that wont work out.
Kind regards
Tobias
You can connect two electrolytic capacitors in series with their minus terminals connected together. To be sure that there is no excessive negative voltage a diode should be connected parallel to the both capacitors. Too much negative voltage will blow up the capacitor with dangerous consequences to your health.
The losses of electrolytic capacitors when used to filter other than DC tend to be quite high and it may be that you eventually end up using film capacitors, like the industry does. The ESR of the film capacitors is quite low that makes the losses in the capacitor easier to handle. However, you may need an extra damping resistor to decrease the ringing of the filter. Or you can do the damping with the control of the inverter that gives the best efficiency.
Hi,
It is not common using electrolytic capacitors for AC filtering. There are some specific AC filter capacitors like polyester or film capacitors.
Electrolytic capacitors have a tangens delta of 10% up to about 300Hz, and between 10 kHz and 1Mhz they are mainly resistive. The loss is about 0.1*(rms current)^2*impedance. The tolerance is typically -30 / +50% at 100 Hz and much more for other frequencies. Their lifetime is short at higher temperatures. They are a kind of RC transmission line. Read the data sheets well and you will never use an electrolytic capacitor for filtering...
Sina, Indeed film capacitors and ceramic types are the choice. Polypropylene is often the best: tangens delta of about 0.1% at 1kHz.
Above 10kHz we expect the tangens delta to increase with root of frequency, but still OK.
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