This is the data I could find: Descriptions
Descriptions of STMicroelectronics S0817NH provided by its distributors.
THYRISTOR, 8.0A 800V TO-220;
Thyristor/Triac Type:Thyristor;
RMS Current It:8A;
Current Itsm:80A;
Current Igt:4mA;
Voltage Vgt:1.5V;
Case Style:TO-220;
Av Current It:5.1A;
Voltage Vrrm:800V