Engineers at Siemens Energy & Automation, Alpharetta, Ga. (www.sea.siemens.com/ motors), were given a clean sheet of paper and 140 years of experience building motors and told to design a line of efficient motors rugged enough to withstand the toughest industrial environments. The result: The SD100 Series of cast-iron-frame NEMA motors. The engineers minimized heat sources inside the motor, then provided the best cooling system. It includes finned frames with fewer areas for dirt buildup, high-flow fans and a fan cover that increase airflow, and a stator core and rotor that work together to remove heat from inside the frame. The oversized, shielded bearings in the motor use a special polyureabased grease with four times the lubrication life of other polyurea greases. The bearings are also dynamically balanced to reduce vibrations, and the bearing housings at each end of the motors are precision machined for accurate alignment between bearings and the rotor.

High-capacity insulation protects against moisture, corrosion, and electrical shock. It includes penetrating varnish on the windings and an inverter-rated NEMA Class F nonhygro-scopic system with a Class-B temperature rise at a 1.0 service factor. The housing is zinc-plated with a stainless-steel nameplate.