Background and overview
JR Hokkaido inserted the additional trailer intermediate vehicles, class saha721-4100 and saha721-4200, into existing 3-car sets of 721-1000 series used on "Airport" rapid services to make them 6-car sets and to obtain surplus 721-0 series vehicles which replaced superannuated 711 series EMU. Modified 721-1000 series vehicles were reclassified into -4100 subseries. Four 6-car sets consisting of 2 powered vehicles and 4 trailer vehicles were delivered over the period from October 2003 until December.
Car body
The vehicle design has a 21200mm long and 2900mm wide body incorporating the lightweight stainless-steel construction. The underseal is applied 3mm thicker than that of 721-0 series. Bodies are unpainted and have an olive-green waistline and headline bands running the length of each car below and above the windows. The cab end section constructed by whether proof steel is fitted with the gangway door and curved surface windscreens on the front. A classification rollsign is fitted above the gangway door. A pair of clusters of the head light and the taillight covered the glass to keep the visibility even if covered with snow are fitted above the windscreens. The additional headlights are also fitted under the windscreens. Anti-fall plates between vehicles are additionally introduced excepting the cab end. The cab end section is painted in silver, having an olive-green waistline band and around the windscreens are painted in black. Class saha721-4200 vehicles have a blue waistline band and red narrow band running the length of each car below the windows and vertical blue bands running outward of both ends of doors. Vehicles converted from 721-1000 series and class saha721-4200 vehicles are equipped with three 1000mm wide single-leaf automatic stepped sliding doors and two fixed windows, a drop window, and a door case window incorporating polycarbonate plate are fitted between the sliding doors. On the other hand, newly built class saha721-4100 are equipped with three 1000mm wide single-leaf automatic stepped sliding doors which can be operated manually by pushing the buttons fitted beside the door and two fixed windows and a drop window incorporating polycarbonate plate are fitted between the sliding doors. The door operating equipment is TK103A fitted above the door header of the sliding doors. A roller-binding destination screen is fitted on each side of the body and the louver of the snow separator employing the cyclone to remove airborne snow from intake for cooling the traction motor is also fitted on each side of the powered vehicles. Newly built class saha721-4100 and saha721-4200 vehicles are equipped with an air conditioner, N-AU722, using R407C refrigerant and rated at 30,000kcal/h on the centre of the roof and 1mm thick stainless cover plates between equipments fitted under their floor to reduce the waving for preventing snow and ice from sticking thereon. On the other hand, the other vehicles are equipped with an air conditioner, N-AU721A, rated at 23,000kcal/h on the centre of the roof.
Bogies
Motored bogies are N-DT721A, trailer bogies applied for class kuha721-4100 and kuha721-4200 are N-TR721A, and trailer bogies applied for class saha721-4100 and saha721-4200 are N-TR721B. N-TR721B employs the reinforced bogie frame and the low fitting position of the bolster suspension since the bolster suspension is interrupted by the doorstep. These bogies feature bolster-less secondary air suspension, axle arm type journal box supporting system, single link traction gear, and the anti-yaw dampers to ensure smooth ride characteristics even at 130km/h. Twin Disc (TD) flexible joint employing deflecting plates made of carbon-fiber reinforced plastic (CFRP) is applied for power transmission device. The gear ratio is 5.19 to get high acceleration performance at the range of middle and high speed and the maximum service speed at 130km/h. Their bogies employ double tread brake riggings.
Traction unit and ancillary equipments
Class moha721-4100 and moha721-4200 vehicles are equipped with a traction
system, N-CI721A, which consists of a thyristor phase control converter
featuring hybrid bridge rectifier and a 3-step Variable Frequency Drive
(VFD) employing Gate Turn Off (GTO) thyristor. This traction system controls
4 AC induction motors, N-MT785A, with a power output of 215kW on truck
basis. Class moha721-4100 and moha721-4200 vehicles are also equipped with
a traction resistor unit, N-MR721, for rheostatic brake, a cross-arm type
current pickup, N-PS721B, and a vacuum circuit breaker, N-CB721, on the
roof and a traction transformer, N-TM721B, beneath the floor. Furthermore,
trailer end vehicles, class kuha721-4200, and intermediate trailer vehicles,
class saha721-4100, are equipped with a motor-driven air compressor, N-MH1785-C2000ML
beneath the floor. Class kuha721-4200 vehicles are also equipped with an
auxiliary power supply, N-APS721B, with a power output of 8kVA beneath
the floor, and class saha721-4100 vehicles are N-APS721A with a power output
of 4.25kVA. The brake system is the electric command pneumatic brake with
not regenerative brake but rheostatic brake.
Accommodation
Class saha721-4200 vehicles having U seat accommodation have partition walls and automatic doors to separate the passenger rooms and the doorways and their accommodation consists of 2-2 abreast reclining seating with 1030mm seating pitch. Conductor's rooms are located at the front end of the body. An LED display for providing passenger information is fitted above the door between the doorway and the passenger room. Class saha721-4100 vehicles having standard seat accommodation don't have the partition walls and automatic doors to separate the passenger rooms and the doorways and their accommodation consists of the mixture of the longitudinal bench seating beside the sliding doors and 2-2 abreast switchable transverse seating with 910mm seating pitch between the longitudinal bench seating. The other standard class vehicles have partition walls and double leaf sliding doors to separate the passenger rooms. Seating accommodation consists of 2-2 abreast switchable transverse seating with 910mm seating pitch at the centre and 1-1 abreast seating at the ends. The seating fabric of class saha721-4100 vehicles is coloured in dark gray and that of the other standard class vehicles is coloured in brown. Straps are fitted above the longitudinal bench seating. Class kuha721-4200 vehicles are equipped with wheelchair space toward the front of the front passenger room, and a Japanese style toilet employing a chemical holding tank, and a water tank at the rear of the vehicle. On the other hand, class saha721-4100 vehicles are equipped with wheelchair space and a universal access toilet employing a chemical holding tank at the rear of the vehicle.
Modification
Vehicles converted from 721-1000 series are additionally fitted with 1mm thick stainless cover plates between equipments fitted under their floor to reduce the waving for preventing snow and ice from sticking thereon.
Operations
721-4100 series entered "Airport" rapid services in 2003. They are also used on the regional services on the Sapporo, Chitose, and Sassho lines. |
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