The Terasaki XS250hs XS Series air circuit breaker is a critical component in marine power systems, designed for specific high-demand applications where both high fault tolerance and easy maintenance are paramount.
Here is a detailed overview of its role and significance in marine environments.
Model Designation Breakdown: XS250hs
• XS250: 250 Ampere frame size.
• h: High Breaking Capacity.
• s: Withdrawable or Slide-out version.
In essence, the XS250hs is a 250A, withdrawable air circuit breaker built to interrupt extremely high fault currents, controlled by an intelligent S-Type trip unit.
Key Features & Marine Significance
1. High Breaking Capacity ('h' Rating):
◦ Marine Significance: This is the defining feature. On a ship, electrical systems are "stiff" with high available fault current, especially near the main switchboard. The XS250hs is engineered to safely interrupt these severe short-circuit faults (its Ultimate Breaking Capacity Icu could be 100kA, 150kA, or more at 440V). This makes it suitable for protecting circuits directly downstream from the main busbar.
2. Withdrawable Design ('s' Version):
◦ Marine Significance: Operational continuity is critical at sea. The withdrawable mechanism allows for:
■ Safe Testing: The TEST position enables simulation of protection functions without disrupting the connected load.
■ Quick Replacement: If a fault occurs, the breaker can be racked out to DISCONNECTEDand a spare swapped in rapidly, restoring power without needing to shut down the entire switchboard section. This is vital for mission-critical systems.
3. S-Type Electronic Trip Unit (Standard on 'hs'):
◦ This intelligent trip unit provides the precise, adjustable protection required for a coordinated marine network:
■ Long-Time Delay (L): Protects cables from overload.
■ Short-Time Delay (S): Ensures selectivity. It can be set to delay momentarily, allowing a downstream breaker (e.g., on a motor starter) to clear a fault first, preventing unnecessary blackouts.
■ Instantaneous (I): For ultimate protection against catastrophic faults.
■ Ground-Fault (G): Essential for marine safety, protecting against insulation failure and reducing fire/electrical shock risk.
4. Marine Environment Durability:
◦ Terasaki breakers are built with corrosion-resistant materials and coatings to withstand the salt-laden, humid, and vibrating environment of a ship.
Typical Applications in Marine Power Systems
The combination of a 250A frame, high-breaking capacity, and withdrawable design makes the XS250hs ideal for protecting significant individual loads or small power distribution groups. Common applications include:
• Large Motor Feeders: Direct protection for high-power motors such as:
◦ Fire Pumps
◦ Ballast Pumps
◦ Large Hydraulic Pumps
◦ Cargo Oil Pumps (on tankers)
◦ Bow Thrusters (smaller vessels or as a secondary feeder)
• Specialized System Switchboards: Acting as the main incoming breaker for a dedicated switchboard powering a critical system (e.g., a dedicated switchboard for reefer containers).
• High-Capacity Auxiliary Feeder: Supplying a sub-distribution board that powers a concentrated area of high electrical load.