Westinghouse DA 50 1200A MO DO LS

The Westinghouse DA 50 1200A MO DO LS air circuit breaker is a robust low‑voltage power protection device originally produced by Westinghouse Electric & Manufacturing Company for heavy commercial and industrial electrical distribution systems. Engineered on the proven DA‑50 frame, this breaker is designed to deliver reliable switching and fault interruption performance for systems with continuous current demands up to 1200 A in 3‑phase applications, typically within the 480–600 V AC range.

Mechanical Operation & Design
Built with a manually‑operated (MO) mechanism, the DA 50 allows operators to open and close the breaker using a local handle or link, providing direct control over the circuit in facilities without remote electrical actuation. The draw‑out (DO) configuration enhances safety and serviceability by enabling the breaker to be withdrawn from the switchgear compartment for inspection, testing, or maintenance without disconnecting the main bus. This reduces downtime and simplifies servicing in large power distribution assemblies.

Protection and Coordination
The “LS” designation indicates the breaker’s provision for Long‑time and Short‑time trip functions—typically implemented through modular trip units or retrofit electronic trip modules—offering enhanced protection beyond basic overcurrent detection. Long‑time protection guards against sustained overloads, while short‑time protection introduces intentional delay coordination for improved discrimination among protective devices in series. Many installations upgrade DA 50 breakers with modern LSIG (Long‑time, Short‑time, Instantaneous, Ground‑fault) trip units for even more precise coordination and ground‑fault detection.

Construction and Performance
The DA 50’s rugged mechanical architecture incorporates heavy copper contacts, spring‑charged operating mechanisms, and arc interruption chambers designed to withstand repeated switching cycles and high fault currents typical in industrial environments. The breaker’s durable frame and components contribute to long service life, reliable performance, and simplified retrofit opportunities for updated protection electronics.

Legacy and Applications
Although Westinghouse no longer manufactures new DA series breakers, many DA 50 units remain in service in older switchgear installations due to their proven mechanical reliability. They are widely used in:

Industrial plants and manufacturing facilities
Large commercial buildings
Utility service entrances and distribution centers
Motor control centers and feeder breakers
Retrofit applications with modern protection upgrades

Specialized service companies often refurbish, test, and retrofit Westinghouse DA 50 breakers with current electronic trip units, helping extend the operational life of legacy switchgear while improving protection performance and coordination.

Westinghouse DA 50 1200A MO DO LS Air Circuit Breaker, Manual operator (MO) and electrical operator (DO), LS (long-time, short-time) trip unit, Line and load terminal connectors, Arc chutes and interrupters, Control wiring harness, Racking mechanism or mounting cradle (if applicable), Test or calibration certificate (if included), User manual and installation guide, Safety and compliance documentation, Manufacturer warranty card, Original Westinghouse packaging