A single-phase full converter is a type of AC to DC converter that can convert the AC input voltage into a variable DC output voltage. The converter consists of four thyristors that are arranged in a bridge configuration. The load connected to the converter can be resistive (R load) or inductive (RL load).

One Quadrant Converter:
- A single-phase full converter using an R load is classified as a one-quadrant converter.
- In this configuration, the load is purely resistive, meaning it does not contain any inductance or capacitance.
- The converter can operate in either the first or third quadrant of the voltage-current characteristic plane.
- In the first quadrant, both the input voltage and output voltage are positive, and the load current is positive.
- In the third quadrant, the input voltage is negative, the output voltage is positive, and the load current is negative.
- The converter can control the magnitude and direction of the average output voltage by adjusting the firing angle of the thyristors.

Two Quadrant Converter:
- A single-phase full converter using an RL load without freewheeling diode (FD) is classified as a two-quadrant converter.
- In this configuration, the load contains inductance (L) and does not have a freewheeling diode connected in parallel with the load.
- The converter can operate in the first and fourth quadrants of the voltage-current characteristic plane.
- In the first quadrant, both the input voltage and output voltage are positive, and the load current is positive.
- In the fourth quadrant, the input voltage is positive, the output voltage is negative, and the load current is negative.
- The absence of the freewheeling diode causes the load current to reverse its direction during the negative half-cycle of the input voltage.
- This configuration allows bidirectional power flow, making it suitable for applications such as regenerative braking in motor drives.

In summary, a single-phase full converter using an R load is classified as a one-quadrant converter because it operates in either the first or third quadrant. On the other hand, a single-phase full converter using an RL load without a freewheeling diode is classified as a two-quadrant converter because it operates in the first and fourth quadrants.