Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

preventing damage to electrolytic capacitors

Status
Not open for further replies.
Z

Zak28

Advanced Member level 2
Joined
Aug 19, 2016
Messages
579
Helped
6
Reputation
12
Reaction score
6
Trophy points
18
Activity points
4,681
Can electrolytics be damaged when attached in this manner
img.png

The capacitor represents a power supplies output cap filter bank which is constantly charged but was reversed attached to a power battery.

It doesn't seem it should cause any damage to the electrolytics since the voltage across it doesn't permit it being reverse charged but Im not sure about this if it would not be damaged by this arrangment.
 

It doesn't seem it should cause any damage to the electrolytics since the voltage across it doesn't permit it being reverse charged
Click to expand...

Sure about this? I would rather expect exploding capacitors after a short while.
 

wiring backward:

aluminum electrolytic will get hot and may explode.
if you're lucky, the pressure relief will spew hot electrolyte and it won't explode

tantalum electrolytic will not work and it will look like you put a small voltage zener diode in the circuit instead of a capacitor

not meeting voltage specification
this will also destroy the capacitor. likely also by heating, so get same result.
lucky if it doesn't explode
 

Surely reverse bias can damage the cap. In the last couple weeks I've been lucky enough to witness this a couple times. They get hot then spew gasses at you.


That said I might expect a power supply to have reverse protection diodes on its output which would prevent such an event.
 

My very first electronic circuit that I built, back as a freshman in high school, was a battery eliminator for a car radio that I wanted to use in my room.

Unfortunately and because of my ignorance, I wired the capacitor backwards. When I powered it up, the radio's light was very dim and the volume low.
Needless to say, I did not own a multimeter back then. So I only noticed that the diodes were very warm. Wondering what could be happening, I noticed on the corner of my eye that the capacitor was bulging. Instinctively, I backed away, just in time as the capacitor blew away.

So, I do know -as sure as the sun will rise every morning- that electrolytic capacitors definitively do not like reverse voltages.
 

As well as respecting polarity, consider the 'ripple rating' and ESR of really big electrolytics.
If abused, they can be remarkably unforgiving...

FWIW, one of the 'linear' supplies I met had a SES incandescent lamp 'in line' to moderate in-rush to its many-tens-of-thousands micro-farad capacitor bank. Also, a couple of high-ish Ohm 'safety' resistors bridged the bank, to be sure, to be sure there'd be no lurking zap due 'dielectric recharge'.

With regard to ESR, the inherently high ESR 'mega bank' was flanked by several ~100 uf with much lower ESR, and a quorum of 0.1 uf with RF-rated ESR.

IIRC, 'dielectric recharge' is related to electrets, of which I've only read, but the precise mechanism seems unclear...
Much info may be proprietary.
YMMV.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top