Square D manufactures three types of overload relays, the melting alloy, the bimetallic, and solid state PT = t. This document also includes application data and approximate dimensions SIRIUS 3/4 Siemens Industry, Inc. Industrial Control Product CatalogOVERLOAD RELAYS Overload Relays Generaldata 7/Siemens IC·Available — 1) The E Electronic Overload Relay is the next generation basic-tier electronic overload relay. The tripping threshold of the overload relay is situated at (±) x rated current.