AH-50C
Terasaki
Refurbished
| Manufacturer | Terasaki Electric Co., Ltd., Japan |
| Product Name | Air Circuit Breaker (ACB) |
| Type / Model | AH-50C |
| Series | Terasaki AT / AH series ACB |
| Rated Current (IEC) | 5000 A (as shown on the nameplate close-up) |
| Frequency | 50–60 Hz |
| Classification Rule | LR (Lloyd’s Register) |
| Serial No. / Date | 02152-501 / 2003-1 (photographed unit) |
| Over-Current Trip | Front-mounted over-current trip unit with adjustable dials – exact type number not clearly visible in the supplied photograph |
| PCB / Board Number | Not clearly visible in the supplied photograph |
| Country of Manufacture | Not verified (Japanese manufacturer; Japanese-language labels) |
| Equipment Type | Low-voltage marine / industrial power distribution |
| Condition | Refurbished |
The Terasaki AH-50C is a heavy-duty, high-capacity air circuit breaker built for the main switchboards of ships and large industrial plants. With a nameplate rating of 5000 A, an interrupting capacity of up to 120 kA and Lloyd’s Register (LR) marking, it is the type of breaker used to connect main generators and protect the main bus bars of a vessel’s electrical system.
Terasaki Electric of Japan is one of the best-known names in marine switchgear, and AH-series breakers are still installed on many vessels built in the 1990s and 2000s. When one of these breakers fails, owners need an exact-match replacement that fits the existing cradle, bus-bar connections and control wiring. SM MARINE SERVICE™ supplies the AH-50C and related Terasaki ACB spare parts to ships worldwide – send your inquiry through https://www.smmarineservice.com/.
An air circuit breaker (ACB) is a low-voltage power breaker that interrupts current in open air, using arc chutes to extinguish the arc when its main contacts separate. On board ship, ACBs are the main protective devices between the generators and the main switchboard, and on large feeders such as bow thrusters, cargo pumps or shore connection.
The AH-50C combines a spring-operated closing mechanism, heavy main contacts and arc chutes with a front-panel over-current trip unit. The trip unit monitors current through the breaker’s current transformers (CT ratio 5000:3 on the nameplate) and opens the breaker automatically on overload or short circuit, protecting generators, cables and bus bars. Operating instructions and connecting diagrams are stored behind the rating nameplate, as marked on the unit.
Front view of the Terasaki AH-50C ACB showing the nameplate, over-current trip unit and charging handle.
| Type | AH-50C Air Circuit Breaker |
| Rated Current (IEC) | 5000 A |
| Frequency | 50–60 Hz |
| Ambient Temperature | 45 °C |
| CT Ratio | 5000 : 3 |
| Interrupting Capacity (Sym.) with INST. | AC 550 V: 100 kA / 460 V: 120 kA / 220 V: 120 kA |
| Interrupting Capacity (Sym.) with MCR | 550 V: 100 kA / 460 V: 100 kA |
| Without INST. | 70 kA |
| Short-Time Current | 100 kA, 1 sec |
| Weight (nameplate) | 220 kg / 364 kg (breaker / with draw-out cradle – not verified) |
| Rule | LR |
| Number of Poles, Control Voltage | Not verified |
Values are read from the nameplate of the photographed unit. Always confirm the rating and control voltage against your switchboard drawings before ordering.
Buyers often search for an individual module when only one part of the breaker has failed. The main assemblies of the AH-50C are:
The electronic over-current release on the upper front panel, with adjustable dials for pick-up and time settings, alarm/trip contacts and test terminals. Its internal electronic board carries the protection logic. The exact trip-unit type number is not clearly visible in the supplied photograph. Terasaki over-current trips of this generation are often found with designations such as AOR-1L; compatibility with the AH-50C must be checked against the unit’s label.
Built-in CTs that feed the trip unit with a signal proportional to the main current.
Optional coils that open the breaker on loss of voltage or on a remote trip command. Terasaki UVT devices such as the AUT-1BDR are used on breakers of this family – fitment not verified.
The stored-energy mechanism that closes the breaker; motor charging is used where remote closing (e.g. auto-synchronising) is required.
Signal contacts for breaker position to the switchboard and power management system (an “Auxiliary Switch (Option) Connection” label is fitted on the unit).
The current-carrying and arc-extinguishing parts, plus the cradle and primary disconnects that connect the breaker to the bus bars.
The AH-50C belongs to the Terasaki AT/AH ACB family, which also includes models such as AH-40C, AH-60C, AT20L and AT25L. SM MARINE SERVICE™ can also assist with these and with current Terasaki ACB ranges.
Nameplate close-up: Terasaki AH-50C, IEC 5000 A, 50–60 Hz, LR, short-time current 100 kA 1 sec.
Safety: an ACB of this size controls very high fault energy. Work only with the generator stopped, the breaker drawn out and isolated, springs discharged and under a permit-to-work system, following Terasaki procedures and class requirements.
SM MARINE SERVICE™ supplies Terasaki AH-50C air circuit breakers and related ACB spare parts – over-current trip units, UVT and shunt-trip coils, charging motors, auxiliary switches, contacts and arc chutes – to ship owners and ship managers worldwide. Depending on availability we can offer refurbished, used, reconditioned or new equipment.
For an accurate quotation, please send:
Availability and condition are confirmed at the time of quotation. Contact us through www.smmarineservice.com.
Main switchboard breakers are built into the switchboard: the cradle, bus bars, control wiring and protection settings are all designed around the original type. Replacing a single AH-50C with the same model avoids modifying the switchboard, re-engineering protection and new class approval – which makes an exact replacement the fastest and most economical way to return a vessel’s power plant to full service.
A 5000 A air circuit breaker made by Terasaki Electric of Japan for marine and industrial main switchboards.
Mainly as a main generator or bus-tie breaker in the main switchboard.
According to the nameplate: 100 kA at AC 550 V and 120 kA at 460 V / 220 V with instantaneous trip; short-time current 100 kA for 1 second.
The nameplate of the photographed unit shows rule “LR” (Lloyd’s Register).
An electronic Terasaki over-current trip mounted on the front panel. Please send a photo of the trip-unit label so we can match the exact type.
Yes, individual trip units and spare parts can be quoted subject to availability.
This listing is for a refurbished unit; condition and availability are confirmed with the quotation.
Terasaki AH-40C, AH-60C, AT20L and AT25L belong to the same ACB family.
Common causes are an uncharged spring, a de-energised UVT or closing coil, or an interlock. Check these before suspecting the mechanism.
Yes. SM MARINE SERVICE™ arranges worldwide shipping to vessels and ports.
The Terasaki AH-50C is a 5000 A, 50–60 Hz air circuit breaker for marine and industrial main switchboards, with up to 120 kA interrupting capacity, 100 kA / 1 sec short-time rating, an adjustable over-current trip unit and Lloyd’s Register marking. It is widely used as a main generator and bus-tie breaker on ships. SM MARINE SERVICE™ supplies refurbished Terasaki AH-50C ACBs and matching spare parts – trip units, coils, motors and contacts – worldwide. Contact us today for availability and price.
SM MARINE SERVICE™
Marine Automation & Navigation Equipment Supplier
Available Equipment Conditions: New • Used • Refurbished • Reconditioned
Specific product condition and availability are subject to confirmation.
Stock Locations: Bangladesh • China
Services: Worldwide Shipping • Technical Support • Spare Parts Supply • Marine Equipment Sourcing
Samir Market, DT Road, Pahartali, beside CDA Market, Chattogram, Bangladesh
Mobile / WhatsApp / Viber: +88 01818 929292
Email: info@smmarineservice.com
Website: https://www.smmarineservice.com/
Need a Terasaki AH-50C, a matching trip unit or any other marine switchboard equipment? Send us your requirement today for a fast quotation and worldwide delivery.
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