A Thyristor is a solid-state semiconductor device with four alternating N and P-type material layers. They act as bistable switches, conducting when their gate receives a current trigger, and continue to work while they are forward biased. Thyristors are synonymous with Silicon-Controlled Rectifier (SCR).

https://www.tme.eu/Document/a3f2a732350872eddd8f8a3aa9bbd52d/BT151-500C.pdf

Features BT151 Thyristor:

1. High reliability
2. High surge current capability
3. High thermal cycling performance
4. The average on-state current of 7.5A
5. Maximum gate trigger current of 15mA
6. The maximum gate trigger voltage is 1.5V
7. Holding current is 20mA
8. RMS on-state current is 12A
9. Repetitive peak off-state voltage of 800V
10. Non-repetitive peak on-state current of 120A

Specifications BT151 Thyristor:

Package Includes:

1 x WeEn Semiconductors Co., Ltd, BT151-800R, Thyristor, 800V 7.5A, 15mA 3-Pin, TO-220AB