Background and overview
Intercity services on the Tsugaru-Kaikyo Line were provided from its opening in 1988 by the "Hatsukari" intercity service, operated with 485 series EMUs, and the "Kaikyo" rapid service, operated with Oha51series coaches. In 2003, JR Hokkaido developed the 789-0 series intercity AC electric multiple unit (EMU) for "Super Hakucho" services linking Hachinohe and Hakodate, replacing the aging Class ED79 electric locomotives and Oha51 series coaches previously used on "Kaikyo" services.
The 789 series trainsets were configured as modular half-sets: a two-car unit consisting of a trailer end car (Class Kuroha789-100) and a powered intermediate car (Class Moha788-100), and a three-car unit consisting of a trailer end car (Class Kuha789-200) and two powered intermediate cars (Class Moha789-200 and Class Moha788-200). These half-sets were coupled to form five-car or eight-car trainsets depending on service requirements.
Car body
The carbody of the 789-0 series measures 20,800 mm in length and 2,900
mm in width, with a bogie centre distance of 14,400 mm. It shares the same
cross-sectional profile as the Kiha261 series DMU, designed to accommodate
up to 3 degrees of tilting. The structure is primarily composed of lightweight
stainless steel, except for the bolster beams, end sections of the centre
beam, and selected cross members, which are fabricated from corrosion-resistant
steel plate.
Externally, the 789-0 series differs noticeably from the earlier Kiha261-0 series in adopting bead-less exterior panels for a smoother appearance. In addition, the floor panels are 2 mm thicker than those of previous models, which contributes to reduced noise levels during operation in the Seikan Tunnel.
The cab ends are constructed from 3.2 mm thick steel plate and feature a gangway door and a high-mounted driver's cab for improved protection against level crossing obstacles. The cab exterior is painted in JR Hokkaido's corporate colour—light green—and bears the "HEAT789 Hokkaido Express Advanced Train" logo. A built-in classification headboard is mounted on the gangway, flanked by vertically arranged headlights using halogen bulbs and high-intensity discharge (HID) lamps. Additional HID lamps are installed above the windscreen, with taillights positioned behind it. For public use of the front gangway during emergency or rush-up operations, an adapter for bellows connectors can be fitted.
Each car is equipped with 700 mm wide single-leaf stepped sliding doors. These doors use pneumatic cylinders to press the door panels against the frame, preventing ice intrusion and mitigating pressure fluctuations. Side windows include small fixed double-glazing units for each first-class seat and wide fixed double-glazing windows aligned with two-seat bays in standard class. All side windows are reinforced with polycarbonate to prevent breakage.
Class Moha789-200 vehicles are equipped with a telephone room featuring
a shunting control position, while Class Moha788-100 vehicles include a
conductor's room with a hinged door and shunting controls. Three-colour
LED destination indicators (red, green, and orange) are mounted on the
carbody sides.
Each car is fitted with two roof-mounted N-AU789 air-conditioning units rated at 19,000 kcal/h. Fresh air is supplied to the passenger compartment via electric fans integrated into the air-conditioning system, replacing conventional roof ventilators.
To prevent snow and ice accumulation, 1 mm thick stainless-steel cover plates are installed between underfloor equipment. The bottom level of underfloor components is limited to a height of 234 mm, which is 49 mm higher than on previous models.
Bogies
The powered bogies are designated as type N-DT789, and the trailer bogies
as type N-TR789. Both types feature bolster-less secondary air suspension,
a trailing arm-type journal box support system, a single-link traction
device, and yaw dampers to ensure smooth ride characteristics even at speeds
up to 140 km/h.
The wheel diameter is reduced to 810 mm to lower the vehicle's centre of
gravity. Power transmission is achieved via Twin Disc (TD) flexible joints
incorporating deflecting plates made of carbon-fiber-reinforced plastic
(CFRP). The gear ratio is set at 3.96, providing high acceleration performance
across medium- and high-speed ranges, with a maximum service speed of 140
km/h.
The bogies are equipped with double-tread brake rigging, while trailer bogies additionally incorporate disc brake rigging.
Traction unit and ancillary equipments
Class Moha788-100 and Moha788-200 vehicles are equipped with traction systems N-CI789-1 and N-CI789-2, respectively. Each system consists of a three-level converter employing Intelligent Power Modules (IPMs) and a two-level variable-frequency drive (VFD), also using IPMs, to control four N-MT731 AC asynchronous traction motors per truck, each rated at 230 kW.
Class Moha789-200 vehicles are equipped with traction system N-CI789-3, which employs Insulated Gate Bipolar Transistors (IGBTs) and a two-level VFD to control the traction motors on a per-truck basis. All traction systems feature field-oriented control.
Powered intermediate cars of Class Moha788-200 are fitted with a forced-air-cooled traction transformer (N-TM789-FN) beneath the floor, supplying power to both Moha788-200 and Moha789-200 vehicles. In contrast, Class Moha788-100 vehicles are equipped with a self-cooled traction transformer (N-TM789-AN) utilizing traveling wind, supplying power exclusively to Moha788-100 vehicles.
Powered vehicles are equipped with underfloor devices to remove airborne snow from intake air. Class Moha788 vehicles are fitted with a roof-mounted single-arm pantograph (PS789) for current collection.
End cars, Class Kuroha789-100 and Kuha789-200, are equipped with an ancillary power supply unit (N-APS789), which includes a rectifier composed of a hybrid bridge circuit combining diodes and thyristors. This unit is powered via the tertiary winding of the traction transformer and supplies 100 V DC at 12 kW. Additionally, an IGBT inverter using pulse-width modulation (PWM) provides two 100 V AC output circuits, mounted beneath the floor.
End cars are also equipped with a motor-driven reciprocating air compressor (N-MHI785-C2000M) installed beneath the floor.
The 789 series features an electrically commanded braking system with regenerative
braking capability, including a holding brake function and trailer-priority
brake control logic. End cars are equipped with ATC-L and ATS-N onboard
signaling systems mounted beneath the floor. Acceleration performance is
2.5 km/h/s in ATC-controlled sections and 1.8 km/h/s in ATS-N-controlled
sections, with automatic switching based on the signaling system..
Accommodation
All seats are adjustable reclining types. First-class vehicles feature 1+2 abreast seating with a pitch of 1,145 mm, while standard-class vehicles have 2+2 seating with a pitch of 960 mm. First-class seats are upholstered in navy leather and equipped with a power outlet located beneath the windowsill and a reading light mounted under the luggage rack.
The door between the vestibule and passenger saloon is automatic, activated by a photo sensor. Above this door, an LED display provides passenger information. Cabin lighting consists of alternating fluorescent lamps and halogen fixtures.
Class Kuroha789-100 vehicles include a catering room and a multipurpose room. A segregated smoking room is provided in Class Moha788-100 vehicles. Western-style toilets with chemical holding tanks are installed in Class Kuroha789-100, Moha789-200, and Kuha789-200 vehicles. The toilet in Class Kuroha789-200 is designed for universal access, and Class Kuha789-200 is additionally equipped with a flush urinal.
Class Moha788-100 vehicles are fitted with a conductor's room featuring
a shunting control position, while Class Moh789-200 vehicles include a
telephone room with shunting controls.
Additional delivery
In 2005, JR Hokkaido delivered a second batch of 11 vehicles to increase
capacity on "Super Hakucho" intercity services operating on the
Tsugaru-Kaikyo Line. Six trailer intermediate cars (Class Saha789-100),
each equipped with a shunting control position, were delivered to be inserted
into existing two-car sets, converting them into three-car formations.
Additionally, three new two-car sets—each consisting of a trailer end car (Class Kuha789-300) and a powered intermediate car (Class Moha788-300)—were delivered to form eight-car trainsets for peak-season operations. The newly designed Class Moha788-300 vehicles are structurally similar to the existing Class Moha788-200, with the minor addition of a prepared shunting control position.
Class Moha789-300 vehicles are equipped with traction system N-CI789-3, which consists of Insulated Gate Bipolar Transistors (IGBTs) and a two-level variable-frequency drive (VFD) controlling traction motors on a per-truck basis. These vehicles also feature a forced-air-cooled traction transformer (N-TM789-FN) mounted beneath the floor.
Due to the inclusion of additional trailer cars, the acceleration performance of the trainsets was reduced to 2.2 km/h/s.
Modifications
In 2007, the designated smoking room was converted into a free-access space.
Following the discontinuation of "Super Hakucho" intercity services
in advance of the Hokkaido Shinkansen opening, JR Hokkaido modified the
789-0 series vehicles for reintroduction into "Lilac" intercity
services between Sapporo and Asahikawa. As part of these modifications,
the ATC-L onboard signaling system was removed and replaced with the ATS-DN
system. The holding brake function was also discontinued.
The louver on the carbody side, originally part of the intake system for
airborne snow removal equipment, was covered with a protective plate, and
additional air intake ducts were installed. The built-in classification
headboard was replaced with a full-colour LED destination display..
Operations
The 789-0 series EMUs entered service in 2002 on "Super Hakucho"
intercity services linking Hachinohe and Hakodate. Following the opening
of the Tohoku Shinkansen extension from Hachinohe to Shin-Aomori on 4 December
2010, "Super Hakucho" services were reorganized to operate between
Shin-Aomori and Hakodate via Aomori.
In March 2016, "Super Hakucho" services were discontinued ahead
of the opening of the Hokkaido Shinkansen, and all 789-0 series vehicles
were formally withdrawn from this route.
Subsequently, surplus six-car sets of the 789-0 series were relocated to
the Sapporo Depot and reassigned to "Lilac" intercity services
between Sapporo and Asahikawa, replacing the aging 785 series EMUs. The
789-0 series is currently in operation on "Lilac" services. |
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