What is an Integrated Gate-Commutated Thyristor (IGCT)?

An Integrated Gate-Commutated Thyristor (IGCT) is a power semiconductor device used for switching current in industrial applications. It operates on principles similar to those of the Gate Turn-Off Thyristor (GTO) and is fully controllable via a gate signal for both turn-on and turn-off.

Development of IGCT

IGCT was jointly developed by Mitsubishi Electric and ABB. Structurally, it resembles a GTO but features enhanced controllability. The gate driver circuit is typically integrated with the gate unit, ensuring efficient switching performance.

Component Description

IGCT is a specialized gate-controlled power device, integrating its gate unit with a Gate Commutated Thyristor (GCT) wafer component. This tight integration ensures rapid commutation of the conduction current from the cathode to the gate.

The IGCT wafer functions similarly to a GTO and can be turned on and off using gate signals. It also supports a high voltage rise rate (dv/dt), eliminating the need for snubber circuits in most applications.

Structurally, IGCT is similar to a GTO but differs in several ways:

• Smaller component size
• More robust gate connections, reducing inductance in the gate and drive circuits
• Extremely high gate current and rapid dI/dt rise rates, preventing the use of conventional wiring between the gate drive circuit and the IGCT

To address these requirements, the gate drive circuit is integrated into the device’s packaging. The drive circuit is positioned around the component, with large ring-shaped conductors connected to the IGCT’s edges. The increased conduction area and reduced distance minimize resistance and inductance.

Performance and Operating Frequency

Compared to GTOs, IGCTs offer significantly faster turn-off times, allowing operation at higher frequencies. For short-duration applications, IGCTs can operate in the kHz range. However, due to high switching losses, the typical operating frequency is limited to 500 Hz.

Applications

IGCTs are primarily used in variable frequency drives (VFDs) and can also power traction motors. Additionally, IGCTs can be connected in series or parallel to handle higher power applications.