Connecting polarised capacitor with wrong polarity - what happens?

ganesh p · 2012-09-18T09:17:24+00:00

I wonder what happens if a polarised capacitor is connected with the wrong polarity. Will it burst?

Connecting polarised capacitor with wrong polarity - what happens?

ganesh p

Member

Updated: Oct 27, 2024

Views: 1.4K

I wonder what happens if a polarised capacitor is connected with the wrong polarity. Will it burst?

0

Replies

Howdy guest!

Dear guest, you must be logged-in to participate on CrazyEngineers. We would love to have you as a member of our community. Consider creating an account or login.

Replies

Abhishek Rawal

Member • Sep 18, 2012

The Capacitor will explode with small puffy smoke & volcano kinda burst.
I have seen it, It's somewhat entertaining.
DO try it, at your home ;-)

Are you sure? This action cannot be undone.
Cancel
Ramani Aswath

Member • Sep 18, 2012

The dielectric in such capacitors is an integral oxide film produced by anodizing the anode (aluminium or tantalum foil) at a voltage about 10% higher than the rated voltage of the capacitor. This oxide film is insulating. To ensure that the film is intact and self repairing, an electrolyte is kept in an absorbent medium between the anode and cathode.
The film is destroyed if the voltage is reversed and only a bare metal results. What this means is that the capacitor becomes a short for reverse voltage. The increase in current electrolyses the water in the electrolyte producing oxygen and hydrogen gas which builds up pressure inside the sealed enclosure and explodes as graphically described by TSH above.
(happy Ganesh Chaturthi! Couldn't resist that)

Are you sure? This action cannot be undone.
Cancel
ganesh p

Member • Sep 18, 2012

bioramani
The dielectric in such capacitors is an integral oxide film produced by anodizing the anode (aluminium or tantalum foil) at a voltage about 10% higher than the rated voltage of the capacitor. This oxide film is insulating. To ensure that the film is intact and self repairing, an electrolyte is kept in an absorbent medium between the anode and cathode.
The film is destroyed if the voltage is reversed and only a bare metal results. What this means is that the capacitor becomes a short for reverse voltage. The increase in current electrolyses the water in the electrolyte producing oxygen and hydrogen gas which builds up pressure inside the sealed enclosure and explodes as graphically described by TSH above.
(happy Ganesh Chaturthi! Couldn't resist that)
can you give explanation why capacitor short circuits when connected with reverse polarity?

Are you sure? This action cannot be undone.
Cancel
Abhishek Rawal

Member • Sep 18, 2012

A reversed voltage changes the dielectric (basically an insulator) into a conductor resulting in short-circuiting the capacitor.

Are you sure? This action cannot be undone.
Cancel
Ramani Aswath

Member • Sep 18, 2012

ganesh p
can you give explanation why capacitor short circuits when connected with reverse polarity?
The dielectric is an anodic film. IF polarity is reversed this film disappears due to the reversed electrochemical reaction. Without the dielectric capacitance also disappears. You can have a capacitor made that has the film on both electrodes. This will work either way. However, It will be almost double the size for the same capacitance.

Are you sure? This action cannot be undone.
Cancel
arunchary

Member • Sep 21, 2012

one more operation may happens when you considers if capacitor changes its polarity motor get exited in opposite direction , so other situations may considers such that capacitor may get damages ....

Are you sure? This action cannot be undone.
Cancel
Ramani Aswath

Member • Sep 22, 2012

arunchary
one more operation may happens when you considers if capacitor changes its polarity motor get exited in opposite direction , so other situations may considers such that capacitor may get damages ....
Are you sure. As far as I am aware of, motor capacitors are the non polarised type. Polarised capacitors are generally the large valued ones used mainly for filtering, wave form smoothening and such.

Are you sure? This action cannot be undone.
Cancel
arunchary

Member • Sep 22, 2012

yes sir i have tested in the case of wet-grinders when i placed a capacitor in an opposite polarity, it starts rotating in anticlockwise direction.

Are you sure? This action cannot be undone.
Cancel
Ramani Aswath

Member • Sep 22, 2012

I think that we are talking of different things. Polarised capacitors are usually electrolytics. They have a positive and negative terminals. What you are mentioning is that the capacitor is placed on one line or the other of the power supply, not just fixing the capacitor in reverse. In your case the phase shift will be 180 degrees the other way and so the motor reverses. This happens because the rotating magnetic field reverses.

Are you sure? This action cannot be undone.
Cancel
naveee

Member • Sep 22, 2012

bioramani
I think that we are talking of different things. Polarised capacitors are usually electrolytics. They have a positive and negative terminals. What you are mentioning is that the capacitor is placed on one line or the other of the power supply, not just fixing the capacitor in reverse. In your case the phase shift will be 180 degrees the other way and so the motor reverses. This happens because the rotating magnetic field reverses.
if polarity changes magnetic field reverses sir ????

Are you sure? This action cannot be undone.
Cancel
Ramani Aswath

Member • Sep 23, 2012

The capacitor on a single phase motor shifts the phase on one of the windings so that in effect the motor becomes a two phase motor. However, if the capacitor is shited the motor reverses.
Please read the section on split capacitor motor here:
#-Link-Snipped-#

Are you sure? This action cannot be undone.
Cancel
arunchary

Member • Sep 24, 2012

yes exactly....sir

Are you sure? This action cannot be undone.
Cancel
arunchary

Member • Sep 24, 2012

yes exactly sir...........

Are you sure? This action cannot be undone.
Cancel