20 HP Electric Motor, Marathon Electric 1750 RPM 230/460V 3 Phase 256T Frame Design B, ZL V256TTDC7026BA S / H128

This is a Marathon Electric three-phase AC squirrel-cage induction motor rated 20 HP on a NEMA 256T frame. The enclosure is drip proof (open drip-proof), meaning the housing has ventilation openings positioned so that liquid or solid particles falling within 15 degrees of vertical cannot enter and reach the windings. ODP construction runs cooler and costs less than a totally enclosed fan-cooled (TEFC) motor of the same rating, but it is limited to clean, dry, indoor locations, whereas TEFC units are used where dust, moisture, or washdown is present. It is a NEMA Design B motor, the standard general-purpose torque and starting-current classification used for fans, blowers, pumps, compressors, conveyors, and machine tool drives. Windings are dual voltage at 230/460 V with a nine-lead connection (the nameplate carries the low-voltage and high-voltage connection diagrams), drawing 52 A at 230 V or 26 A at 460 V. Full load speed is 1750 RPM on 60 Hz, which is a 4-pole design. Service factor is 1.15, insulation is Class B, duty is continuous at up to 40 C ambient, and the bearings are a 309 at the shaft end and a 208 at the opposite end.

The nameplate string reads as a date code prefix followed by the model. ZL is the Marathon date code letter pair for October. V occupies the protector-code position and indicates no inherent thermal overload protector is fitted. 256T is the NEMA frame size. TDC is the type designation, also printed separately in the TYPE field: T for three-phase squirrel cage, D for drip proof enclosure, C for cast iron frame construction. 7026 is the design sequence number identifying the 20 HP 4-pole rating within the frame, and 3AS are Marathon revision and manufacturing characters that do not affect the electrical rating. H128 is the Marathon catalog number, and A66680-66 is the nameplate identification number.