Fw: [Boatanchors] rotor starting capacitor

[Troglodite at aol.com]

In a message dated 7/7/04 10:41:38 PM Central Daylight Time,  
brianclarke01 at optusnet.com.au writes:

"If we can acceptably 'fake' an AC capacitor by using a diode bridge,  that's
convenient, but surely manufacturers do not use internal diode bridges  in
their motor-start capacitors."
 
Though at first it looks possible, you cannot "fake" an AC capacitor with a  
diode bridge. After a couple of cycles, the capacitor will simply charge to 
the  peak voltage, and from then on no current will flow. The same thing happens 
if  you put diodes across a pair of series capacitors to block the reverse 
current  flow - both capacitors charge up to the peak voltage, and after that no 
current  flows. A motor starting capacitor works by using capacitive 
reactance to shift  the phase. Current must flow in both directions - shifted in phase 
from the  voltage.