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The integrated gate-commutated thyristor (IGCT) is a power semiconductor electronic device, used for switching
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...
in industrial equipment. It is related to the gate turn-off (GTO) thyristor. It was jointly developed by
Mitsubishi The is a group of autonomous Japanese multinational companies in a variety of industries. Founded by Yatarō Iwasaki in 1870, the Mitsubishi Group historically descended from the Mitsubishi zaibatsu, a unified company which existed from 1870 ...
and ABB. Like the GTO thyristor, the IGCT is a fully controllable power switch, meaning that it can be turned both on and off by its control terminal (the
gate A gate or gateway is a point of entry to or from a space enclosed by walls. The word derived from old Norse "gat" meaning road or path; But other terms include ''yett and port''. The concept originally referred to the gap or hole in the wall ...
). Gate drive electronics are integrated with the thyristor device.Eric Carroll, "IGCTs: Moving on the Right Track", ''Power Electronics Technology'', Aug 1, 200

retrieved on January 8, 2010.


Device description

An IGCT is a special type of
thyristor A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials used for high-power applications. It acts exclusively as a bistable switch (or a latch), conducting when the gate receives a current ...
. It is made of the integration of the gate unit with the Gate Commutated Thyristor (GCT) wafer device. The close integration of the gate unit with the wafer device ensures fast commutation of the conduction current from the cathode to the gate. The wafer device is similar to a gate turn-off thyristor (GTO). They can be turned on and off by a gate signal, and withstand higher rates of voltage rise (dv/dt), such that no snubber is required for most applications. The structure of an 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 a complete elimination of minority carrier injection from the lower PN junction and faster turn-off times. The main differences are a reduction in cell size, and a much more substantial gate connection with much lower inductance in the gate drive circuit and drive circuit connection. The very high gate currents and fast dI/dt rise of the gate current mean that regular wires can not be used to connect the gate drive to the IGCT. The drive circuit 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 is used. The large contact area and short distance reduce both the inductance and resistance of the connection. The IGCT's much faster turn-off times compared to the GTO's allows it to operate at higher frequencies—up to several kHz for very short periods of time. However, because of high , typical operating frequency is up to 500 Hz. Neutron-Transmutation-Doped Silicon used as the IGCT base substrate. IGCTs, in high power applications, are sensitive to cosmic rays. To decrease cosmic ray induced malfunctions, more thickness in the n base is required.


Reverse bias

IGCT are available with or without reverse blocking capability. Reverse blocking capability adds to the forward voltage drop because of the need to have a long, low-doped P1 region. IGCTs capable of blocking reverse voltage are known as symmetrical IGCT, abbreviated S-IGCT. Usually, the reverse blocking voltage rating and forward blocking voltage rating are the same. The typical application for symmetrical IGCTs is in current source inverters. IGCTs incapable of blocking reverse voltage are known as asymmetrical IGCT, abbreviated A-IGCT. They typically have a reverse breakdown rating in the tens of volts. A-IGCTs are used where either a reverse conducting diode is applied in parallel (for example, in voltage source inverters) or where reverse voltage would never occur (for example, in switching power supplies or DC traction choppers). Asymmetrical IGCTs can be fabricated with a reverse conducting diode in the same package. These are known as RC-IGCT, for reverse conducting IGCT.


Applications

The main applications are in variable-
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
inverters, drives, traction and fast AC disconnect switches. Multiple IGCTs can be connected in series or in parallel for higher power applications.


See also

*
Thyristor A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials used for high-power applications. It acts exclusively as a bistable switch (or a latch), conducting when the gate receives a current ...
* Gate turn-off thyristor * Insulated-gate bipolar transistor


References

{{Reflist


External links


'IGCT Technology-A Quantum Leap', pdf
Solid state switches