440VAC 480V NEMA 3 industrial-grade, magnetic replacement AC Operating Control Coil.The primary electrical function of this component is to generate a localized electromagnetic field that physically pulls down the heavy mechanical contacts inside an industrial motor starter assembly.This specific dual-frequency variant is factory-configured to operate on a continuous input threshold of 480V AC at 60Hz or 440V AC at 50Hz.The physical construction features a precision copper-wire winding structure encapsulated in a durable structural compound to resist high vibration and constant thermal cycling.The coil is designed with 2 screw terminal connection points and is engineered specifically to actuate NEMA Size 3 contactors and motor control loops rated for high-current 90A configurations.Industry Equivalents (Cross-References)The Southland Electrical Supply 73A288-R serves as a direct, precise aftermarket replacement coil built specifically to mirror the physical layout dimensions and electrical impedance curves of the Allen Bradley component.The Rockwell Automation 40526 series represents the broader industrial reference platform from the factory hierarchy managing identical structural footprints.The Joslyn Clark Size 3 Replacement Coils can be adapted within broad custom industrial backplanes as an operational alternative, assuming input potentials and physical housing parameters align.The Furnas / Siemens 45DH20 functions as an alternative high-voltage NEMA Size 3 class control coil, matching the primary 480V control loop activation properties for automated plant assemblies.History of the ComponentThe lineage of this component belongs to Allen-Bradley, an elite powerhouse in industrial automation and power management founded in 1903 and subsequently acquired by Rockwell Automation in 1985. The 73A series coils (specifically Series K) were engineered during the peak expansion of heavy electromechanical factory control panel lines throughout the mid-to-late 20th century.Before the advent of micro-scale solid-state relays, factory floors relied on heavy-duty magnetic contactors to safely activate massive high-horsepower industrial pumps, conveyors, and manufacturing fans. Because these magnetic coils undergo constant electrical stress, internal heat build-up, and mechanical wear, Allen-Bradley made the coils fully modular so that maintenance teams could slide out a burnt-out coil and drop in a fresh one without replacing the entire expensive contactor chassis.The original manufacturer officially discontinued production of this specific part on October 31, 2006, declaring it an obsolete/legacy item. Despite its EOL status, the immense population of active legacy machinery worldwide ensures that the 73A288 remains heavily managed across surplus, refurbishment, and third-party industrial distribution databases.Actual Product Applications (Makes and Models)The Allen-Bradley Bulletin 702 AC Contactor (Size 3) integrated the 73A288 coil directly into its lower mechanical core assembly to pull down the primary heavy-duty electrical contacts when activated by an incoming 480V pilot loop.The Allen-Bradley Bulletin 709 Magnetic Motor Starter (Size 3) utilized this operating coil within its multi-pole housing to act as the core electro-magnetic switch driving large three-phase industrial motors.The Allen-Bradley Bulletin 705 Reversing Contactor Matrix regularly employed these coils in paired configurations, safely stepping between forward and reverse directional phase cycles for complex assembly cranes and factory lift gear.
