The Terasaki XS100hs is another key model from the Terasaki XS Series of Air Circuit Breakers (ACBs), but it serves a different role in a marine power system compared to the larger XS250ns.
Here is a detailed breakdown of the Terasaki XS100hs and its specific applications in marine electrical systems.
Overview: Terasaki XS100hs
The model name "XS100hs" decodes as follows:
• XS: Series name.
• 100: The frame size, indicating a rated current of up to 1000 Amps. (The actual setting is determined by the rating plug installed).
• hs: This suffix is critical. It denotes a breaker with a very High Breaking capacity and a Short-time withstand capability. The "hs" model is engineered specifically for systems where fault currents can be extremely high.
Key Specifications (Typical for XS100hs):
• Rated Current (Iu): Up to 1000A.
• Rated Operational Voltage (Ue): Typically 690V AC.
• Breaking Capacity (Icu/Ics): This is the standout feature. The XS100hs has an exceptionally high breaking capacity for its frame size, often 100kA or more at 415V. This makes it suitable for locations very close to the main generators or busbars where available fault current is at its maximum.
• Tripping Unit: Features a sophisticated Electronic Trip Unit (ETU) with fully adjustable protection settings for overload, short-circuit, and ground fault.
Application in Marine Power Systems
While the XS250ns is often a Main Generator Breaker or Bus Tie Breaker, the XS100hs is typically found one level down in the distribution hierarchy, protecting major feeder circuits.
Its primary roles are:
1. Large Feeder Circuit Protection:
◦ It is the ideal breaker for supplying power to large, individual loads that require a high-current feed but are not as large as the main generators.
◦ Key Examples:
■ Bow Thrusters / Stern Thrusters: These are among the largest motor loads on a ship and have very high starting currents.
■ Large Cargo Pumps (on tankers).
■ HVAC Plant Motors: The central chilling water plants on large vessels.
■ Cargo Handling Cranes (on offshore supply vessels or general cargo ships).
■ Main Switchboard (MSB) to Sub-Switchboard Feeder: It can act as the incoming breaker for a large sub-switchboard that distributes power to a specific zone of the ship (e.g., accommodation, engine room, fore ship).
2. High Fault Current Locations:
◦ Due to its "hs" (high breaking capacity) rating, it is used in parts of the switchboard where the calculated available fault current is too high for a standard breaker. Its design ensures it can safely interrupt a severe short-circuit without being destroyed.
3. Engine Room Auxiliary Systems:
◦ It can protect the main feeders for large auxiliary systems like the central cooling water pump motors, fire pump motors, or fuel oil supply units.
Why the XS100hs is a Critical Component
1. Selective Coordination (Discrimination):
◦ The fully adjustable ETU is crucial for achieving selective coordination. The time-current curves of the XS100hs can be set to ensure it trips after a downstream breaker (like an MCCB on a thruster motor starter) for a fault on the thruster circuit. This isolates the problem without taking out the entire feeder, which could black out other critical equipment on the same sub-board.
2. Current Limiting Performance:
◦ Like the rest of the XS series, the XS100hs is a current-limiting breaker. It interrupts a fault in the first half-cycle of the current wave, drastically reducing the thermal and magnetic stress (I²t) on cables, busbars, and connected equipment. This is a major safety and asset protection feature.
3. Marine Environment Durability:
◦ It shares the same robust construction as the larger XS models, with corrosion-resistant treatments and designs to withstand vibration, shock, humidity, and salt air, complying with marine classification society standards (Lloyd's, DNV, ABS, etc.).
Comparison with the XS250ns
Feature
Terasaki XS100hs
Terasaki XS250ns
Frame Size
1000A
2500A
Primary Role
Major Feeder Breaker
Main Generator / Bus Tie Breaker
Typical Loads
Thrusters, Large Pumps, Sub-Feeders
Main Generators, Main Bus Sections
Key Characteristic
Very High Breaking Capacity (Icu) for its size
Very High Continuous Current rating
System Level
Secondary Distribution (downstream of main bus)
Primary Generation & Distribution
Summary
The Terasaki XS100hs is a compact powerhouse within the XS Series. Its combination of a 1000A frame and an exceptionally high breaking capacity makes it the perfect choice for protecting the ship's most demanding auxiliary loads and feeder circuits. It ensures that faults in large motors or sub-distribution boards are contained locally, maintaining the overall integrity and availability of the ship's electrical power system.