Reliance Electric 78155-77R Rectifier Gate Stack

Reliance Electric 78155-77R Rectifier Gate Stack is a high-power gate-drive module designed for use inside rectifier stacks of legacy Reliance Electric drive systems (Baldor Reliance/ABB). Identified by part number 78155-77R, this assembly functions as the gate stack that controls the thyristors/SCRs within a rectifier module, enabling regulated DC output in industrial motor drives. The part is listed by multiple suppliers as "rectifier gate stack" and is noted by manufacturers and distributors as discontinued. Originating from Reliance Electric, a historic brand now part of Baldor Reliance (ABB), the 78155-77R designation appears in several surplus listings and drive-repair catalogs. Because it is discontinued, the item is typically encountered on the secondary market as surplus or used equipment, with listings that describe it as a complete gate stack assembly for a Reliance rectifier. When considering an exchange or retrofit, verify that the gate-stack interface matches your drive's rectifier assembly and that any associated heat-dissipation components align with your equipment's cooling configuration. Given its age, this part is primarily of value to technicians repairing or retrofitting older Reliance/Baldor drive systems where a 78155-77R gate stack is required for compatibility.