Voltage regulation:

Ideally, the average rectifier output voltage should remain constant. But practically it varies with the changes in the load current. Voltage regulation is defined as:

$Voltage\ regulation\ =\ \dfrac{V_{NL}-\ V_{FL}}{V_{FL}}\times{}100\%$

Where VNL = Average load voltage at no load i.e. when RL = ∞

$\therefore{}\ V_{NL}=\frac{V_m}{\pi{}}$

No load voltage is the value of average output voltage at zero load current and VFL i.e. the full load voltage is the value of average output voltage at the specified maximum load current.

$V_{FL}=Average\ load\ at\ full\ load=\dfrac{V_m}{\pi{}}\dfrac{R_L}{(R_S{+R}_F{+R}_L)}$

Substituting the expressions for VNL and VFL in the equation of voltage regulation, we get load regulation as,

$Load\ regulation=\dfrac{\dfrac{V_m}{\pi{}}-\dfrac{V_m}{\pi{}}\dfrac{R_L}{\left(R_S{+R}_F{+R}_L\right)}\ }{\dfrac{V_m}{\pi{}}\dfrac{R_L}{\left(R_S{+R}_F{+R}_L\right)}}=\dfrac{\dfrac{V_m}{\pi{}}\left(R_S{+R}_F{+R}_L-R_L\right)}{\dfrac{V_m}{\pi{}}R_L}\ $

And

$\therefore{}Voltage\ Regulation=\dfrac{\left(R_S{+R}_F\right)}{R_L}\times{}100\% $

Ideally the load regulation should be 0% and practically it should be as low as possible. A rectifier with lowest value of regulation should be preferred.

Ripple factor:

It is defined as the ratio of the rms value of the ac component in the load to the steady DC component.

The rectifier output consists of AC as well as DC components. The ripple factor measures the percentage of AC component in the rectifier output. The ripple factor indicates how close the rectified output is to the ideal dc voltage waveform. Small values of ripple factor indicate that the rectified output waveform is close to being pure dc. The ideal value of RF should be zero and practically it should be as small as possible.

$Ripple\ factor\ =\ \ \dfrac{RMS\ value\ of\ the\ AC\ component\ of\ output}{DC\ or\ average\ value\ of\ the\ output}\ $