K-WANG
ABB 2032-04-16-06 The Integrated Gate Commutated Thyristor
ABB 2032-04-16-06 The Integrated Gate Commutated Thyristor
DESCRIPTION
The outstanding feature of the IGCT - leading to its name and its main advantages - is not only the silicon wafer itself, but the way it is driven by the gate - the electrical and mechanical gate-drive design. The «hard- drive» concept at the heart of IGCT operation requires the mechanical integration of gate driver and semiconductor into one single unit with low circuit inductance. It also implies a number of new converter features, which make IGCT converters different from GTO or IGBT converters. It is the scope of this application note to make designers familiar with the data sheets and the use of IGCTs in their main application areas.
The following features are important to remember:
• no turn-off snubber is needed in applications without series connection; where turn-off snubbers are used, they are considerably smaller than those of GTOs
• the customer control interface is reduced to a power supply, an optical control input and an optical status feedback output
• gate drive geometry is an important parameter in mechanical stack design.
Data sheet user’s guide
This section is a detailed guide to the correct understanding of an IGCT data sheet. Parameters and ratings will be defined and illustrated by figures where appropriate, while following the sequence in which parameters appear in the data sheet. For explanation purposes, data and diagrams associated with IGCT type 5SHY 55L4500 have been used, but because all IGCTs have similar data sheets, this guide is applicable to all IGCTs. Additionally a 5SHX 26L4520 data sheet is used to explain the diode parameters of reverse-conducting devices. The data sheets distinguish between maximum rated values and characteristic values. Maximum rated values indicate limits beyond which damage to the device may occur. Characteristic values are parameters defined under typical application conditions.
Key features
·High snubberless turn-off rating
·Optimized for medium frequency
·High electromagnetic immunity
·Simple control interface with status feedback
·Ac or Dc supply voltage
·Option for series connection (contact factory)
Thermal data
In addition to the thermal data of the IGCT, the data sheets of reverse conducting IGCTs have thermal data for the diode part. The data is documented in the same way as in section 2.6. Rth and Zth are specified without heat flow between the GCT-part and diode-part.
IGCTs in Voltage Source Inverters (VSI)
Reverse conducting IGCTs (RC-IGCT), asymmetric IGCTs (AS-IGCT) and their corresponding diodes are qualified and tested in test circuits built according to the circuit diagram below. It is an equivalent circuit for the switching events occurring in a VSI circuit, be it of 2-level or 3-level topology.
Determining the value of the di/dt limiting inductor
In a VSI, as in most power electronic circuits, a diode turn-off is caused by an IGCT turn-on and the diode’s turn-off di/dt capability is, in most cases, lower than the turn-on di/dt capability of the IGCT. This is especially true in common applications without a turn-off snubber. Hence the di/dt choke LI must be large enough to allow operation within the di/dt range of the diode even at the highest DC-link voltages. Typical values for ABB diodes are between 200 and 1000 A/µs depending on diode wafer size and switching voltage. Diode switching losses and surge currents are also dependent on the choke size and these considerations may require a larger inductance value. This, however, will come at the cost of a slower clamp circuit transient (tdyn) and longer switching dead times.
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