Best Answer: At 50 Hz. frequency, impedance offered by 2200 uF capacitor to ac ripples will be = 1/ (2pi*50*2200*10^-6) or = 10^6/ (2*22/7*50*2200) = 1.446 ohms, If power supply is delivering 1 amp at 15 volts ( load impedance 15/1 means 15 ohms), capacitor impedance to ripples is 10 times(approx) lessor, it works fine. read more
Personally I have opened up huge amount of power supplies so far, and I can tell you 1000uF is more common than a 2200uF but that doesn't mean they only use 1000uF, for AC noise suppression they use 0.01uF-0.1uF non polar type, for hold up purpose they use maybe 330uF/390uF/470uF/680uF and many other types, in low voltage high current application they even use 4700uF/10000uF. read more
To suppress power supply noise. Either external or self generated. External supply noise either comes from the power supply such as a regulator, which can have switching noise, or from other circuits or motors, etc on the same supply. This noise is often low frequency and needs large caps to suppress it. read more