SCR N1718NC180 is a high-power silicon-controlled rectifier (thyristor) made by IXYS / Littelfuse, designed for demanding industrial power control applications.

In short:
It’s a 1.8 kV, very high-current (up to ~3450 A RMS) phase-control device used to switch and regulate large amounts of electrical power efficiently.

Typical uses:

Industrial motor drives and soft starters
Controlled rectifiers (AC→DC conversion)
Power supplies and converters (e.g., wind or rail systems)
Heavy-duty energy control systems

Littelfuse provides one of the most comprehensive ranges of standard phase control thyristors in the industry. Devices with voltage ranges from 400V to 6500V are available, making them suitable for applications with line voltages from 230V to over 1000V (higher voltage applications are now served by our range of Medium Voltage Thyristors). Littelfuse is a leading supplier of phase control products into demanding markets such as industrial DC drives, controlled rectifiers, marine/rail propulsion systems, wind power converters, electrochemical power supplies and soft starters. These devices are optimised to give low conduction losses and are primarily intended for applications with line frequencies up to 400Hz. The Wespack outline (WPxx) is an innovative concept in phase control thyristors for applications requiring devices rated to 2200V. It gives the maximum power rating for weight and volume without compromising on quality and reliability. It also gives the maximum current rating and lowest thermal resistance for the package size.