Why is the voltage measured at the capacitor in a air conditioning unit greater than the original supply voltage?

 

You need to use a higher rated capacitor in any application. A good general rule is 2 to 1.
So if your circuit is running 12v use a 24v or higher rated cap.

Mike2545

 

Often you are seeing the peak voltage if there is no load. With a rectified sinewave, that is roughly 1.4x the RMS voltage.

 

it could be a voltage multiplier (< wikipedia) or some circuit like that, dunno about air conditioners but maybe it uses something similar to get more voltage/ less current for a component.

 

Why is the voltage measured at the capacitor in a air conditioning unit greater than the original supply voltage?

Because they don't manufacture capacitors with all possible voltage ratings one can use. There are some standard values and designers choose the most suitable for the design. If you use a lower value than the operating voltage it will blow thus they use the next higher value (at least).