This part is a kind of semiconductor called BT138-600.

Function of this product has Bi-Directional Triode Thyristor.

Manufacturers : SemiWell

Image and pinout :

Some of the text within the PDF file :

SemiWell Semiconductor Bi-Directional Triode Thyristor Features ◆ Repetitive Peak Off-State Voltage : 600V ◆ R.M.S On-State Current ( IT(RMS)= 12 A ) ◆ High Commutation dv/dt ◆ Non-isolated Type General Description This device is suitable for AC switching application, phase control application such as fan speed and temperature modulation control, lighting control and static switching relay. BT138-600 Symbol ○ 2.T2 ▼▲ ○ 3.Gate 1.T1 ○ TO-220 123 Absolute Maximum Ratings ( TJ = 25°C unless otherwise specified ) Symbol Parameter Condition VDRM IT(RMS) ITSM I2t Repetitive Peak Off-State Voltage R.M.S On-State Current Surge On-State Current I2t for fusing TC = 101 °C One Cycle, 50Hz/60Hz, Peak, Non-Repetitive t =10ms PGM PG(AV) IGM VGM TJ TSTG Peak Gate Power D [ ... ]

BT138-600 PDF Datasheet Download