Over the past 20 years, IGCTs (Insulated Gate Commutated Thyristors) have been specifically designed for high-power application scenarios and are widely used in motor drives, railway converters, STATCOMs (Static Synchronous Compensators), circuit breakers, and other harsh fields with extremely high reliability requirements. Currently, more than 250,000 IGCTs have been put into long-term operation, demonstrating outstanding reliability performance.

IGCT Design

An IGCT integrates a high-power semiconductor switch and a high-performance gate unit (see Figure 1).

The main components of the gate path are shown in Figure 2.

Version 1

Its high reliability largely benefits from the mature experience of GTO drivers. The control of IGCT is managed optically via command signals, while it also supports confirming the successful execution of switching events through status feedback signals (see Figure 1). This device only requires a single voltage to be supplied to the gate unit for operation. The power semiconductor is packaged in a hermetic ceramic housing using free-floating pressure packaging technology, and this packaging process provides an extremely high level of reliability assurance for the device.

Quality Monitoring Tests

Over the past 20 years, the turn-off capability of IGCT has achieved significant improvement. ABB's quality monitoring scheme is shown in Figure 3, which clearly presents the evolution process of IGCT's turn-off capability.

Version 2

Thanks to the accumulated application experience of GTO drivers, IGCT possesses excellent high reliability. At the control level, IGCT manages command signals in an optical manner, and can also utilize status feedback signals to ensure the successful completion of switching events (see Figure 1). The power supply requirement for the gate unit is simplified, and only a single voltage needs to be connected. The power semiconductor is sealed in a ceramic housing using free-floating pressure packaging technology, and this packaging design effectively ensures the highest reliability level of the device.

Quality Monitoring Tests

In the recent 20 years, the turn-off capability of IGCT has been greatly optimized. Figure 3 shows ABB's quality monitoring plan, which highlights the continuous progress of IGCT in terms of turn-off capability.

Reliability Assessment and Fault Analysis

ABB works closely with end customers to collect and obtain field reliability data. The collected data is shown in Figure 4. The field failure rate in FIT is calculated in accordance with Equation (1).

As shown in Figure 4, the FIT rate has decreased significantly, especially since 2010.

The IGCT failure modes are analyzed and classified into different types, see Figure 5.

Lifetime Assessment

A detailed analysis has been conducted on equipment retrieved after 15 years of operation, as described below: To support the construction of the Gotthard Railway Tunnel in Switzerland, a hoist was installed to lift gravel generated from excavation to a height of 850 meters (see Figure 6). The variation of junction temperature Tvj during the acceleration phase of this hoist is shown in Figure 7.

After the completion of the tunnel construction, the staff removed the medium-voltage (MV) drive and sent the IGCTs inside it to a semiconductor factory for wear analysis. The results show that the cathode metallization of the IGCT devices from the Gotthard project application showed no signs of degradation (see Figure 8). For comparison, in the certification phase of the load cycle test, even if the metal height of the device's cathode segment decreased to 75% of the initial value, such devices could still meet the requirements of the equipment test specification.

IGCTs possess high current capability with low losses and high reliability, making them particularly suitable for medium-voltage drives. In addition, IGCTs feature high inrush current capability and long-term SCFM capability, which offer great potential for power transmission and distribution applications.

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