GATE TURN OFF THYRISTOR GTO

A GTO thyristor can be turned on by a single pulse of positive gate current like conventional thyristor, but in addition it can be turned off by a pulse of negative gate current. The gate current therefore controls both ON state and OFF state operation of the device. GTO V-I characteristics is shown in Figure 2. The GTO has many advantages and disadvantages with respect to conventional thyristor among which few are discussed here.

Figure1: Schematic Symbol of GTO

Figure2: V-I characteristics of GTO

ADVANTAGE OF GTO OVER THYRISTOR

1- Elimination of commutating components in forced commutation resulting in reduction in cost, weight and volume,
2- Reduction in acoustic and electromagnetic noise due to the elimination of commutation chokes,
3- Faster turn OFF permitting high switching frequency,
4- Improved converters efficiency, and,
5- It has more di/dt rating at turn ON.

ADVANTAGE OF THYRISTOR OVER GTO

1- ON state voltage drop and associated losses are higher in GTO than thyristor,
2- Triggering gate current required for GTOs is more than those of thyristor,
3- Latching and holding current is more in GTO than those of thyristor,
4- Gate drive circuit loss is more than those of thyristor,
5- Its reverse voltage block capability is less than its forward blocking capability.