Background and overview
JR East converted 205‑0 series EMUs—displaced from the Chūō–Sōbu Line by the introduction of the E231‑0 series—into 205‑1000 series DC commuter electric multiple unit (EMU) trains between 2002 and 2003. These conversions, which included shortening the formations to two‑car sets, were undertaken to replace the aging 101 series operating on the Nambu Branch Line.
Car body
The carbody of the 205‑1000 series measures 19,715 mm in length and 2,800 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 beam, and selected cross beams, which are fabricated from weather‑resistant steel plate (Steel Plate Atmospheric). The exterior features unpainted bead‑stiffened stainless‑steel panels with waistline and headline bands finished in a combination of blue green and yellow running the length of each car below and above the windows.
Class Kumoha205‑1000 vehicles were converted from Class Moha205‑0 powered intermediate cars, while Class Kumoha204‑1000 vehicles were converted from Class Moha204‑0. These conversions included removing the original end structure and the side panels adjacent to the end windows, welding a reinforced front frame to the cut body end, and mounting a non‑gangwayed high‑strength composite structure—consisting of phenol‑resin foam and paper honeycomb covered with fibre‑reinforced plastic panels—onto the reinforced frame. An obstacle deflector is fitted beneath the cab, and the driver’s cab is elevated 300 mm above floor level to improve forward visibility and provide additional protection against obstacles at level crossings. The horizontally curved windscreen, finished in black at the upper portion with ceramic coating, is installed at the cab end. An LED destination display is mounted centrally behind the upper portion of the windscreen. Lighting equipment consists of two high‑intensity discharge (HID) lamps flanking the destination display and two externally mounted taillights.
Each car is equipped with four double‑leaf automatic sliding doors, each 1,300 mm wide. Door operation is controlled by TK4J units installed beneath the bench seats. Between the doors, the side panels feature pairs of drop windows measuring 920 mm in width, with additional drop windows provided at each end of the carbody. Additional equipment includes a loudspeaker mounted on each side of the carbody to support passenger announcements, as well as a destination rollsign.
Each car is fitted with a roof‑mounted AU75G air‑conditioning unit rated at 42,000 kcal/h. Class Kumoha204‑1000 vehicles are equipped with four roof‑mounted draught ventilators, while Class Kumoha205‑1000 vehicles feature five.
Couplers between married‑pair motored cars use drawbars, while the connections at the cab ends employ tightlock couplers.
Bogies
The powered bogies are designated as DT50 or DT50D, depending on the original vehicles from which they were converted. Both types feature bolsterless secondary air suspension and conical multilayer rubber‑spring journal supports. Traction force is transmitted via the centre pin and multilayer rubber‑spring draw gear. The side beams of the bogie frame are straight in profile, and the bogie transom incorporates seamless pipes to achieve a lightweight and simplified structure.
Power transmission utilizes a parallel cardan‑shaft drive system with a hollow shaft. The gear ratio is 6.07. Corrugated wheels are adopted to reduce weight, and a compound circular wheel profile is employed to minimize lateral forces exerted on the track.
The braking configuration are single‑tread brake rigging.
Powertrain and ancillary equipment
Series‑wound brushed DC traction motors (MT61), each rated at 120 kW, are employed. The eight traction motors on Class Kumoha205‑1000 and Class Kumoha204‑1000 vehicles are controlled by the CS57 armature‑resistance traction control system, which incorporates field‑added excitation control. A naturally ventilated traction‑resistor unit designated as MR159 or MR159A is used. During the armature‑voltage control stage, armature‑resistance control and series–parallel control are applied. During the field‑weakening stage, the HS52 or HS52A field‑added excitation system indirectly regulates the field current by controlling the current of the inductive shunt. Forced‑field control provided by the field‑added excitation system enables regenerative braking. At low speeds, regeneration voltage is maintained through series–parallel control, allowing regenerative braking to remain effective down to approximately 20 km/h. If regenerative‑braking performance falls below the required threshold, pneumatic braking is automatically applied to supplement the braking force.
Current collection is handled by a PS21 lozenge‑type pantograph mounted on the roof of Class Kumoha205‑1000 vehicles. Class Kumoha204‑1000 vehicles converted from Class Moha 204‑0 that were not originally fitted with a motor‑generator unit are additionally equipped with an auxiliary power supply unit (SC72) rated at 160 kVA, as well as the existing motor‑driven air compressor (MH3075‑C2000M), both mounted beneath the floor.
The brake system features an electrically commanded pneumatic braking system with regenerative‑braking capability, resulting in improved brake response. End vehicles are equipped with an onboard ATS‑P signalling system installed in the cab due to space constraints caused by the extensive ancillary equipment mounted beneath the floor.
Accommodation
The passenger saloon of the 205‑1000 series EMU is configured with fully longitudinal seating to maximize capacity and facilitate smooth passenger flow during boarding and alighting. Each bench is fitted with end partition panels to delineate individual seating areas. Hanging straps are installed throughout the passenger compartment to support standing passengers in two parallel rows along the ceiling. The air‑conditioning ductwork is installed above the ceiling to maintain a clean interior profile, with slit‑type vents providing evenly distributed airflow. Illumination is provided by fluorescent fixtures arranged in two parallel rows along the ceiling. The control desk is fitted with a single‑handle master controller operated with the left hand.
Modification
The pantographs of Class Kumoha205-1000 vehicles were replaced with PS33E
single‑arm pantographs in 2009.
Operations
In 2002, the 205‑1000 series entered revenue service on the Nambu Branch Line, operating alongside the remaining 101 series EMUs. An additional two‑car set was converted in 2003 to completely replace the remaining 101 series units.
Subsequently, E127 series EMUs from the Niigata area were transferred to the Nambu Branch Line to replace two aging two‑car sets of the 205‑1000 series. |
|
| Technical Data |
| Items |
Data |
| Supply Voltage |
1,500 V DC |
| Service
speed, etc. |
Acceleration: 2.5 km/h/s Deceleration: 2.8 km/h/s Service speed: 100 km/h |
| Length |
19,500 mm |
| Width |
2,800 mm |
| Height |
4,140 mm |
| Bogie |
DT50/DT50D |
| Collector |
PS33E |
| Traction
motor |
MT61 (120 kW) |
| Gear ratio |
6.07 |
| Traction system |
Field added
excitation control: CS57 |
| Air conditioner |
AU75G (42,000 kcal/h) |
| Designed
by |
JR East |
|
|
