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Aluminum Capacitor

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thepaan

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I bought some of these for my BuckPlus 7023 LED drivers. The data sheet says I should wire them in next ot the buck if the DC power is more than 18 inches away.

The housing seems metal which I didn't really think about when I purchased them. Does that mean it's grounded to the housing? My LEDs aren't but I know a lot of LEDs are grounded to the thermal solder points in the base. Anyway, I wanted to mount them upside down on this heatsink I'm using to mount the LEDs and I don't want to risk electrocuting myself. So, does anyone know if the device is grounded to the casing?
 

KMoffett

Well-Known Member
I don't think so, but just use an Ohm meter to check.

But more importantly, don't mount electrolytic capacitors on the heat sink. Heat is the killer of electrolytics.

Ken
 

thepaan

Member
Wait, what? How is mounting on a heatsink going to make it hot? If anything it should make it colder, right? I couldn't exactly figure out how the calculation for heat transfer should work over a surface area but it's a pretty **broken link removed**. That would be the U81C for the 2U system.

But, good call on the ohm meter. I'll take one to work tomorrow to check.
 
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KMoffett

Well-Known Member
Wait, what? How is mounting on a heatsink going to make it hot? If anything it should make it colder, right? I couldn't exactly figure out how the calculation for heat transfer should work over a surface area but it's a pretty **broken link removed**. That would be the U81C for the 2U system.

But, good call on the ohm meter. I'll take one to work tomorrow to check.

Heat sinks get hotter than the ambient temperature. They transfer the heat from the source to the air through the metal. Sticking your caps on the metal means that they will pick up heat above ambient. Just not a good idea.

Ken
 

crutschow

Well-Known Member
Most Helpful Member
Aren't they already going to be hotter than ambient due to the electrical current being applied?
An ideal capacitor does not dissipate energy, only stores it. Practical capacitors don't get warm unless they are used in high frequency, high ripple current applications such as the output caps on switching regulators. In that case the heat is cased by the ripple currents throught the small parasitic capacitor series resistance (ESR).
 
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