The Schneider Electric WATSNB-250/250-4CBR-X is a 250A, 4-pole (3P+N), Closed Transition (Parallel) Automatic Transfer Switch (ATS). It is a high-performance, microprocessor-controlled unit designed for seamless and reliable power source transfer between two supplies (typically Main/Utility and Backup/Generator) in critical power applications. The "Closed Transition" (CBR) feature enables "make-before-break" switching, allowing uninterrupted transfer without power interruption to the load.
Specifications
Parameter Specification
Product Line WATSNB Automatic Transfer Switch
Rated Operational Current (Ie) 250 A (per pole, for both sources)
Number of Poles 4 Poles (3P + N)
Transition Type Closed Transition (Parallel) - Sources are briefly paralleled during transfer.
Switching Elements Two electrically/mechanically interlocked Molded Case Circuit Breakers (MCCBs) or specially designed contactors.
Rated Voltage (Ue) Typically 400/415V AC, 50/60 Hz (Up to 690V AC possible)
Withstand & Making Capacity High short-time withstand current (Icw) and short-circuit making capacity (Icm) as per breaker specifications.
Control Unit Advanced microprocessor-based controller (indicated by the final "X" character, e.g., "D").
Controller Functions • Voltage & Frequency monitoring of both sources
• Programmable transfer delays (engine cool-down/start-up)
• Closed transition sync-check & parallel time control
• Load shedding/adding management
• Communication capability (Modbus, etc.)
Standards IEC 60947-6-1, UL 1008, CSA
Operation Modes • Auto: Fully automatic operation based on source availability.
• Manual: Local manual control.
• Test/Off: For maintenance and testing.
Mechanical/Electrical Interlocks Prevents simultaneous closure of both source breakers.
Enclosure Typically supplied as a assembled panel or enclosed unit (IP rating varies).