This part is a kind of semiconductor called 10N80.
Function of this product has N-Channel Power MOSFET.
Manufacturers : nELL
Image and pinout :

Some of the text within the PDF file :
SEMICONDUCTOR 10N80 Series RRooHHSS Nell High Power Products N-Channel Power MOSFET 10A, 800Volts DESCRIPTION The Nell 10N80 is a three-terminal silicon device with current conduction capability of 10A, fast switching speed, low on-state resistance, breakdown voltage rating of 800V, and max. threshold voltage of 5 volts. They are designed for use in applications such as switched mode power supplies, DC to DC converters, PWM motor controls, bridge circuits and general purpose switching applications. FEATURES RDS(ON) = 1.1Ω @ VGS = 10V Ultra low gate charge(58nC max.) Low reverse transfer capacitance (CRSS = 15pF typical) Fast switching capability 100% avalanche energy specified Improved dv/dt capability 150°C operation temperature D G D S TO-3PB (10N80B) GDS TO-220F (10N80AF) D (D [ ... ]
10N80 PDF Datasheet Download
