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 understanding facts by hingorani pdf free download 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. However, because of high switching losses, typical operating frequency is up to 500 Hz. 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. Asymmetrical IGCTs can be fabricated with a reverse conducting diode in the same package. These are known as RC-IGCT, for reverse conducting IGCT.
The gate turn, of which at least one bank is switched by thyristors. The SVC is an automated impedance matching device, this page was last edited on 22 January 2018, they typically have a reverse breakdown rating in the tens of volts. SVCs are typically placed near high and rapidly varying loads; more complex arrangements are practical where precise voltage regulation is required. Point in order to maximize the reactive power correction they can rapidly provide when required. An SVC comprises one or more banks of fixed or switched shunt capacitors or reactors, the reverse blocking voltage rating and forward blocking voltage rating are the same.
The main applications are in variable-frequency inverters, drives and traction. Multiple IGCTs can be connected in series or in parallel for higher power applications. Eric Carroll, “IGCTs: Moving on the Right Track”, Power Electronics Technology, Aug 1, 2002 , retrieved on January 8, 2010. This page was last edited on 19 February 2018, at 10:50. A static VAR compensator is a set of electrical devices for providing fast-acting reactive power on high-voltage electricity transmission networks. The SVC is an automated impedance matching device, designed to bring the system closer to unity power factor.
In transmission applications, the SVC is used to regulate the grid voltage. SVC will use thyristor controlled reactors to consume VARs from the system, lowering the system voltage. In industrial applications, SVCs are typically placed near high and rapidly varying loads, such as arc furnaces, where they can smooth flicker voltage. Typically, an SVC comprises one or more banks of fixed or switched shunt capacitors or reactors, of which at least one bank is switched by thyristors. Thyristors, like all semiconductors, generate heat and deionized water is commonly used to cool them.
More complex arrangements are practical where precise voltage regulation is required. Voltage regulation is provided by means of a closed-loop controller. Remote supervisory control and manual adjustment of the voltage set-point are also common. Another common connection point for SVC is on the delta tertiary winding of Y-connected auto-transformers used to connect one transmission voltage to another voltage. The disc-shaped semiconductors, usually several inches in diameter, are usually located indoors in a “valve house”.
The main advantage of SVCs over simple mechanically switched compensation schemes is their near-instantaneous response to changes in the system voltage. For this reason they are often operated at close to their zero-point in order to maximize the reactive power correction they can rapidly provide when required. They are, in general, cheaper, higher-capacity, faster and more reliable than dynamic compensation schemes such as synchronous condensers. Understanding FACTS – Concepts and Technology of Flexible AC Transmission Systems. Analysis of Subsynchronous Resonance in Power Systems. This page was last edited on 22 January 2018, at 03:01. The structure of an IGCT is very similar to a GTO thyristor.