Form factor is defined as the ratio of RMS value to the average value of a waveform. The waveform can be quantity like voltage, current, etc. This parameter is generally used in the rectifiers.
Form factor Formula
$\text{Form factor}=\frac{{A_{rms}}}{{A_{avg}}}$
where,
Arms is the rms value of the waveform
Aavg is the average value of the waveform
Form factor of Half wave rectifier
The RMS value of output current of single-phase half-wave rectifier is given by
$I_{rms}=\frac{I_{m}}{2}$
where, Im is the peak value of output current.
The average value of output current of single-phase half-wave rectifier is given by
$I_{avg}=\frac{I_{m}}{\pi}$
where, Im is the peak value of output current.
As we know that form factor is given by
$\text{Form factor}=\frac{{I_{rms}}}{{I_{avg}}}$
Therefore, we get
$\text{Form factor}=\frac{{\frac{I_{m}}{2}}}{{\frac{I_{m}}{\pi}}}$
∴ Form factor = π/2 = 1.5707963
The form factor of half wave rectifier is 1.5707963
Form factor of Full wave rectifier
The RMS value of output current of single-phase full-wave rectifier is given by
$I_{rms}=\frac{I_{m}}{\sqrt{2}}$
where, Im is the peak value of output current.
The average value of output current of single-phase full-wave rectifier is given by
$I_{avg}=\frac{2I_{m}}{\pi}$
where, Im is the peak value of output current.
As we know that form factor is given by
$\text{Form factor}=\frac{{I_{rms}}}{{I_{avg}}}$
Therefore, we get
$\text{Form factor}=\frac{{\frac{I_{m}}{\sqrt{2}}}}{{\frac{2I_{m}}{\pi}}}$
∴ Form factor = 1.11072073
The form factor of full wave rectifier is 1.11072073
Form factor of Bridge rectifier
The RMS value of output current of Bridge rectifier is given by
$I_{rms}=\frac{I_{m}}{\sqrt{2}}$
where, Im is the peak value of output current.
The average value of output current of Bridge rectifier is given by
$I_{avg}=\frac{2I_{m}}{\pi}$
where, Im is the peak value of output current.
As we know that form factor is given by
$\text{Form factor}=\frac{{I_{rms}}}{{I_{avg}}}$
Therefore, we get
$\text{Form factor}=\frac{{\frac{I_{m}}{\sqrt{2}}}}{{\frac{2I_{m}}{\pi}}}$
∴ Form factor = 1.11072073
The form factor of bridge rectifier is 1.11072073
