1. Input Displacement Angle $\left(\phi_{1}\right)$: The input-displacement angle, denoted by $\phi,$ is defined as the angular displacement between the fundamental component of the a.c. line current and the associated line to neutral voltage. In all phase controlled converter circuits, the fundamental component is either in phase or lags behind the voltage by an angle which depends upon the firing angle.

2. Input Displacement Factor (cos $\phi_{1} )$: The input displacement factor is defined as the cosine of the input displacement angle.

3. Input Power Factor (PF): The input power factor is defined as the ratio of the total mean input power to the total RMS input volt-amperes. Since only the fundamental component contributes to the mean input power, the power factor may be defined as

$$P F=\frac{E_{1} \ I_{1} \ \cos \phi_{1}}{E_{\mathrm{rms}} \ I_{\mathrm{rms}}}=\frac{I_{1}}{I_{\mathrm{rms}}} \cos \phi_{1}$$

where, $$E_{1}=E_{\mathrm{rms}}= \text{phase-voltage}$$ $$I_{1}= \text{fundamental component of the supply current}$$ $$\phi_{1}=\text{input displacement angle}$$ $$I_{\mathrm{rms}}=\text{supply rms current}$$

4. D.C. Voltage Ratio (r): The d.c. voltage ratio, denoted $r,$ is defined as the ratio of the mean d.c.terminal voltage at a given firing-angle $\alpha,$ to the maximum possible d.c. terminal voltage, that is, the voltage obtained when the firing angle is zero degree.

5. Input Current Distortion Factor: The distortion factor of the current in a given input-line is defined as ratio of the RMS amplitude of the fundamental component, to the total RMS amplitude.

6. Input Harmonic Factor $\left(\mathrm{I}_{H}\right):$ The input harmonic factor is defined as the ratio of the total harmonic content to the fundamental component.

$$I_{H}=\frac{\left(I_{\mathrm{rms}}^{2}-I_{1}^{2}\right)^{1 / 2}}{I_{1}}$$

7.Voltage Ripple Factor $\left(K_{V}\right)$: The voltage-ripple factor is defined as the ratio of the net harmonic-content of the output voltage to the average output voltage.

$$K_{V}=\frac{\sqrt{E_{\mathrm{dc}_{\mathrm{rms}}}^{2}-E_{\mathrm{dc}}^{2}}}{E_{\mathrm{dc}}}$$

where $$E_{\mathrm{dc}}= \text{average value of output voltage,}$$

$$ E_{\mathrm{dc}_{\text { rms }}}=\mathrm{RMS} \text { value of output voltage. } $$

8. Current Ripple Factor $\left(K_{I}\right)$: The current ripple factor is defined as the ratio of the net harmonic content of the output voltage to the average output current.

$$K_{I}=\frac{\sqrt{I_{\mathrm{drms}}^{2}-I_{\mathrm{d}}^{2}}}{I_{d}}$$

where $$\quad I_{d}= \text{average value of output-current}$$ $$I_{\mathrm{drms}}=\text{RMS value of the output-current.}$$