capacitors

[cueshark]

i am looking for some cheaper capacitors for some 14000 watt transformers i got. what is the difference betweeb a uF & aMFD capacitor? i know i want around 1800uF @ least 80volts in uF. i need to know if the MFD is the same thing or if it will even work for a power supply? if it will work do i still need 18000 or is there something different about a MFD capacitor? thanks greg

[vladdy]

Just a little tidbit to explain why you see "u" (as in uf) when representing the term microfarads. The u is actually the lower case greek letter "μ" or mu which in the International System of Units represents the prefix micro-. Most use u as it is easier to type a u than it is to pull up the character map, copy it, paste it, etc. Some will use m- to denote micro, more often than not, u is used.
also..
there's also picofarads [pf] and nanofarods [nf]
It breaks down like this. 1uf=1000nf. (So, 100nf = 0.1uf; 10nf=0.01uf 1nf=0.001uf ect.) and 1nf=1000pf, so 1uf = 1,000,000 pf.


--enjoy..

[Al_The_Man]

Originally Posted by vladdy Just a little tidbit to explain why you see "u" (as in uf) when representing the term microfarads. The u is actually the lower case greek letter "μ" or mu which in the International System of Units represents the prefix micro-. Most use u as it is easier to type a u than it is to pull up the character map, copy it, paste it, etc. Some will use m- to denote micro, more often than not, u is used. also.. --enjoy..

Technically M is alot different than µ But it is commonly used, especially in N.A., to indicate the same thing when indicating microfarads.
BTW the easiest way to type in the 'specials' is to use the ALT key.
e.g. ALT 230 = µ ALT 241=± etc.
Al.

[Gootee]

In catalogs, typically, MFD = MF = uF = microfarads.

But MFD and MF are considered archaic and should no longer be used, which also applies to the older MMF and MMFD notations that meant picofarads (micro-micro-farads), now properly denoted by pF.

We now sometimes also see mF used to denote millifarads, e.g. 10 mF = 10000 uF. Personally, I don't like that notation, because it might be ambiguous for someone who was familiar with the older MFD and MF notations.

Just get capacitors with capacitances that are near-enough to what you need, with voltage ratings greater than any voltage they will ever see. And if there will be a large AC current component through them ("ripple current"), look for caps that have the max ripple current specified at the frequencies they will encounter. For use in power supply rectifier circuits, as "smoothing" caps, you might also want to find caps for which the ESR (Equivalent Series Resistance) is specified, and use the caps with the lowest ESR, which will tend to minimize the ripple voltage seen by downstream components, and will also tend to allow the cap itself to withstand larger ripple currents without shortening it lifespan as much.