IGCT Insulated Gate Commutated Thyristor
IGCT is the new member in the power semiconductor family (1997). It was introduced by ABB.
It is a special type of GTO thyristor.
- Similar to GTO, it is a fully controllable power switch. ie, It can be turned-On and turned-Off by applying a gate signal. It has lower conduction losses as compared to GTO thyristors.
- It withstands higher rates of voltage rise(dv/dt). So snubber circuits are not required for most of the applications.
- The main applications of IGCT are in variable frequency inverters, drivers and traction.
- Multiple IGCTs can be connected in series or in parallel for higher power applications.
- The device has been applied in power system inter-tie installations(100MVA) and medium-power(upto 5MW) industrial drives.
- The structure of IGCT is very similar to a GTO thyristor.
- In an IGCT, the gate turn-off current is greater than the anode current.This results in shorter turn-off times.
- The main difference compared with a GTO thyristor is a reduction in cell size, combined with a much more substantial gate connection, resulting in a much lower inductance in the gate drive circuit and drive circuit connection.
- The very high gate currents and the fast dI/dt rise of the gate current means that regular wires cannot be used to connect the gate drive to the IGCT.
- The drive circuit printed circuit board(PCB) is integrated into the package of the device.
- The drive circuit surrounds the device and a large circular conductor attaching to the edge of the IGCT die is used. The large contact area and short distance reduces both the inductance and resistance of the connection.
Types of IGCT:-
- This device is available either with or without reverse blocking capability.
- IGCTs capable of blocking reverse voltage are known as symmetrical IGCTs. The typical application of symmetrical IGCTs is in Current Source Inverters(CSI).
- IGCTs incapable of blocking reverse voltage are known as asymmetrical IGCTs. They typically have a reverse breakdown rating in tens of volts or less. Such IGCTs are used where either a reverse conducting diode is applied in parallel or where reverse voltage would never occur.
- Asymmetrical IGCT can be fabricated with a reverse-conducting diode in the same package. These are known as reverse conducting(RC) IGCTs.
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