Background and overview
Rural services in the Akita region had long been operated by locomotive‑hauled trains, typically formed of only two to three cars outside peak hours.
This operating pattern resulted in insufficient service flexibility, as locomotive-hauled formations required locomotive run-around movements at terminal stations and frequent coupling and uncoupling to adjust train length to demand.
Furthermore, both the locomotives and passenger coaches used on these services had become significantly aging.
To address these issues, JR East initiated the development of a new generation of AC electric multiple unit (EMU) trains—the 701-0 series—intended to replace locomotive‑hauled services and improve operational efficiency on rural lines.
In 1993, JR East introduced thirteen 3-car sets, each comprising one motored car and two trailer cars, and twenty-five 2-car sets, each consisting of one motored car and one trailer car.
Car body
The carbody of the 701-0 series measures 19,500 mm in length and 2,870 mm in width, with a bogie centre distance of 13,800 mm. The structure is primarily composed of stainless steel, except for the bolster beams, the end sections of the centre sill, and selected cross beams, which are fabricated from weather resistant steel plate (Steel Plate Atmospheric).
The body employs Kawasaki’s two-sheet spot-welded stainless-steel structure, in which a pressed inner stainless-steel sheet is spot-welded to an outer sheet. This double-skin construction provides the required rigidity without the use of bead embossing. The exterior consists of unpainted flat stainless-steel panels, complemented by a magenta waistline band, with light and dark magenta bands applied below the windscreens.
The cab end is gangway-equipped, incorporating a gangway door and a low-profile driver’s cab. Flat windscreens are adopted to reduce manufacturing costs. Lighting equipment consists of two sealed-beam headlights mounted above the gangway door and two taillights positioned below the windscreens. A destination rollsign is mounted above the co-driver’s-side windscreen.
Each car is fitted with three 1,300 mm-wide double-leaf automatic stepped sliding doors on each side. Door operation is controlled by TK113C units employing pneumatic direct-drive mechanisms mounted above the door headers. Manual operation is enabled via push-button controls located adjacent to each door.
Between the doors, the side panels are fitted with a horizontal band of four windows, including two double-hung side windows with a height of 960 mm, while fixed windows are installed at each end of the carbody. All windows employ heat-absorbent glass, eliminating the need for blinds.
Traditional roller-blind destination indicators and external loudspeakers—used for platform-side passenger announcements—are installed on each side of the carbody.
A roof-mounted AU710A air conditioning unit, rated at 38,000 kcal/h, is installed at the centre of the roof. No roof ventilators are provided.
End cars are equipped with an automatic jumper coupler to facilitate rapid turn-back operations.
Bogies
The powered bogies are designated DT61A, while the trailer bogies are classified as TR246A. Both bogie types employ bolsterless secondary air suspension and trailing arm link journal box supports. Traction force is transmitted via a single-link draw gear.
Both bogie types incorporate a bow-shaped frame design, adopted to lower the bolster-suspension height and thereby contribute to a reduced floor level. The distance between the two secondary suspension units is 200 mm narrower than on the earlier standard TR235 bogie, allowing the secondary suspension assemblies to be mounted directly onto the side frames, thereby simplifying the bogie frame construction.
Power transmission utilizes Twin Disc (TD) flexible couplings with carbon-fiber-reinforced plastic (CFRP) deflecting plates, with a gear ratio of 7.07.
The braking configuration differs between bogie types: powered bogies are equipped with single-tread brake rigging, while trailer bogies combine single-disc brake units with single-tread brake rigging.
Traction unit and ancillary equipments
Class Kumoha701-0 cars are equipped with the CI1 traction system, which
controls four MT65 three-phase AC asynchronous traction motors on a per-bogie
basis, each rated at 125 kW. The traction system comprises a thyristor/diode
hybrid-bridge traction rectifier and a three-level variable-frequency drive
(VFD) utilizing power transistors.
Class Kumoha701-0 cars are also fitted with an MH1083-DM107 motor generator unit and a TM26 traction transformer, both mounted beneath the floor. The transformer employs a shell-type core with forced oil cooling, and provides a primary voltage of 20 kV, with secondary and tertiary outputs of 825 V and 388 V, respectively. A PS104 cross arm pantograph and an MR102 braking resistor are mounted on the roof.
Class Kuha700-0 end cars are equipped with an MH1112-C1600MF motor-driven air compressor beneath the floor.
The braking system is an electrically commanded brake with rheostatic braking.
Accommodation
Passenger accommodation features longitudinal bench-type bucket seating throughout. Each bench is fitted with end partition panels to reduce cold-air intrusion. The air-conditioning ductwork is installed above the ceiling, maintaining a clean interior profile, with slit-type vents providing evenly distributed airflow.
The cab is a left-side compartment-type design, optimized for conductor-less operation. Two-car sets are equipped with ticket vending machines located near the doorways, as well as fare chart displays and fare boxes positioned behind the driver’s cab. Three-car sets are not equipped with these devices, although provisions for future installation are included. A 1,200 mm-wide double leaf sliding door is fitted at the gangway to facilitate movement between cars during conductor-less operation.
Class Kuha700 trailer end cars are equipped with a western-style toilet incorporating a chemical holding tank. A wheelchair space is provided across the aisle from the toilet.
Modification and refurbishment
Transverse seating bay installation
In 2000, four additional bucket-type transverse seating bays were installed in Kuha700-36 to -38 cars assigned to rural services between Shinjō and Ōmagari on the Ōu Line, as part of service-quality improvements.
Pantograph replacement
The pantographs of Kumoha701-36 to -38 cars operating on the Shinjō-Ōmagari section of the Ōu Line were replaced with PS35A single-arm pantographs in 1998. These were subsequently replaced with PS109 single-arm pantographs.
For all other Class Kumoha701 cars, the pantographs were replaced with PS109 units from 2005 onward.
Equipment refurbishment
JR East upgraded the original CI1 traction system to the CI19 traction unit, comprising a three-level converter and a two-level variable-frequency drive, both employing Insulated Gate Bipolar Transistors (IGBTs). This system controls four asynchronous traction motors on a per-bogie basis. In the event of a traction system failure, one failed unit can be isolated, allowing continued operation.
The traction transformers were replaced with TM32A units, incorporating harmonic-current protection. The braking system was upgraded to an electric-command brake with regenerative braking, enabled by the new traction system, and the braking resistor units were removed.
The roller-blind destination indicators were replaced with LED destination indicators.
Operations
The 701-0 series entered rural revenue service on the Ōu Line and Uetsu Line in the Akita region.
In 2016, one three-car set was severely damaged in a level-crossing collision and was subsequently withdrawn from service in 2020. Two surplus Saha701 intermediate trailer cars, released through the shortening of three-car formations, were also withdrawn.
The 701-0 series is currently deployed on rural services of the Ōu Line between Shinjō and Aomori, the Uetsu Line between Tsuruoka and Akita, and the Tsugaru Line. |
|
