In a R firing circuit with Vgp, the R refers to the resistance component in the circuit, while Vgp refers to the gate pulse voltage.

In a typical R firing circuit, the gate pulse voltage (Vgp) is applied to the gate terminal of the thyristor (or SCR) to trigger its conduction. The resistance component (R) is used to limit the current flowing through the gate terminal, ensuring that the thyristor turns on in a controlled manner.

The value of the resistance (R) is chosen based on the gate circuit characteristics and the desired firing angle. It is important to select the appropriate resistance value to ensure reliable triggering of the thyristor and to prevent excessive current flow, which can lead to damage.

The gate pulse voltage (Vgp) is typically a short-duration pulse applied to the gate terminal. It can be generated by various methods, such as using a pulse transformer or a pulse generator circuit. The timing and duration of the gate pulse voltage are important factors in controlling the firing angle of the thyristor.

In summary, in a R firing circuit with Vgp, the resistance component (R) is used to limit the current flowing through the gate terminal, while the gate pulse voltage (Vgp) is applied to trigger the thyristor's conduction. The values of R and Vgp are selected based on the desired firing angle and the gate circuit characteristics.