WP-S Flameproof Power Wirewound Resistors Welwyn / TT Electronics WP-S Flameproof Power Wirewound Resistors provide flameproof protection and offer enhanced pulse handling capability. These WP-S resistors are small-sized resistors with a 1W to 5W power rating. This Welwyn WP-S series offers a surface mount ZI-form option. The Flameproof Power Wirewound Resistors are RoHS compliant with lead-free terminations.