Semiconductors

Both are high-power semiconductor switches, but they are optimised for different operating points. IGBTs (Insulated Gate Bipolar Transistors) switch faster (up to several kHz) and are well-suited for medium-power applications such as wind turbine converters, solar inverters and industrial drives. IGCTs (Integrated Gate Commutated Thyristors) have lower conduction losses at high current and are optimised for low-switching-frequency, high-power applications such as SFCs, HVDC and large industrial drives. Hitachi Energy offers both in its portfolio, enabling selection of the optimal device for each application.

StakPak is Hitachi Energy’s family of press-pack IGBT and diode modules with a patented spring technology that guarantees uniform pressure across all parallel chips. Press-pack packaging is preferred for HVDC and other series-connection applications because failed devices conduct (short-circuit) rather than open-circuit, enabling the converter to continue operating with a faulty device until planned maintenance. StakPak’s modular concept also simplifies series connection of multiple devices to reach the very high voltages required in HVDC converter valves.

SPT (Soft Punch Through) is Hitachi Energy’s proprietary IGBT chip technology. It combines a high insulation voltage with soft switching performance — meaning the current tail during turn-off is gradual rather than abrupt, reducing electromagnetic interference and switching stress on other components. SPT+ and SPT++ are evolved generations offering improved efficiency and rugged safe operating area (SOA), which is critical for reliable operation under fault conditions. TSPT+ is the latest generation, used in the highest-performance HiPak modules.

Phase control thyristors (PCTs) are used in line-commutated converter applications where extremely low conduction losses at high average current are required — primarily HVDC Classic converter valves, large industrial rectifiers for electrochemical processes (chlorine, aluminium smelting), SVC (Static VAR Compensators) and high-power motor drives. Hitachi Energy’s thyristor range extends to 8,500 V / 4,500 A, covering the most demanding HVDC and industrial applications. A 6,500 V variant in explosion-protected housing is available for hazardous industrial environments.

The IGCT (Integrated Gate Commutated Thyristor) evolved from the GTO (Gate Turn-Off Thyristor) but with key improvements. The IGCT integrates the gate drive unit directly onto the device, enabling much faster turn-off through a hard gate drive that commutates the entire device current in nanoseconds. This eliminates the large snubber circuits required by GTOs, reduces switching losses and simplifies converter design. The IGCT also achieves switching frequencies up to 500 Hz in standard operation, versus the lower frequencies typical of GTOs.

The IGTO(t)™ (Insulated Gate Turn-Off Thyristor) is a new silicon power semiconductor developed by Pakal Technologies and being incorporated into Hitachi Energy’s high-voltage module portfolio. It is the first new high-voltage silicon power semiconductor since the IGBT was introduced in the 1980s. The IGTO(t) delivers 30% lower conduction losses than IGBT at high current and temperature, while maintaining compatibility with existing module architectures. At the system level, this enables higher power density, reduced thermal management requirements and materially improved energy efficiency.

Hitachi Energy offers purpose-designed IGBT modules for electric vehicle traction inverters and on-board chargers. These modules are optimised for the specific operating profile of e-mobility applications: high peak current during acceleration, low losses at typical EV driving points, compact form factor and high power density. The e-mobility module portfolio builds on Hitachi Energy’s SPT+ chip technology and is designed for compatibility with emerging SiC-based system architectures.