The Class 377 Electrostar is a British electric multiple-unit train (EMU) built by Bombardier Transportation at its Derby Works, from 2001 to the present. The Electrostar family is the most numerous type of EMU built in the post-privatisation period of Britain’s railways. The class forms the major part of the Southern fleet.
The units work suburban services in south London, and rural commuter services to Sussex, Surrey, Kent and the South Coast, on which they replaced 4Cig and 4Vep slam-door stock which came to end of their useful lives and which did not meet modern health and safety requirements. Built in the early 2000s, the units had a troubled introduction; being fully air-conditioned, their higher power consumption compared to the slam-door Mark 1-based stock that they replaced led to major upgrades being required to the 750 V DC third-rail power supply used in the former Southern region. The collapse of Railtrack following the Hatfield accident further delayed this upgrade work, and the new stock did not enter squadron service until 2003.
Class 377s are fitted with external CCTV. There is a disabled seating area, and both intermediate coaches have toilets. Bodyside power doors are electrically operated, a move away from the air powered systems of previous generation EMUs. Dual-voltage units are fitted with a Brecknell Willis high-speed pantograph, incorporating a pair of aerofoils on the pan knuckle to steady the pan head against the OLE contact wire. The configuration of a 5-car Class 377 unit is:
DMOC(A) – 2 motors on inner bogie, sander, auxiliary converter module
MOSL – 2 motors on inner bogie, standard toilet
PTSOL – pantograph, transformer, compressor, disabled toilet
MOS – 2 motors on inner bogie, standard class interior (only found on Class 377/6 and 377/7 units)
DMOS(B) – 2 motors on inner bogie, sander, auxiliary converter module
In 4-car units the driving cars are composite, with the first-class saloon between the driving cab and the first set of passenger doors. 4-car units also do not contain the MOS coach.
Mitrac is the Bombardier Train Management System (TMS). It provides monitoring of on-train systems, fault-finding diagnostics, event monitoring, and preventative maintenance. In conjunction with the onboard GPS receiver, Mitrac controls Selective Door Operation (SDO), as well as automatic Passenger Information System (PIS) displays and Public Address announcements. Engineers can access the system remotely via GSM to download the fault log, then carry out real-time diagnostics while the train continues in service.
The Class 377 uses Dellner couplers instead of the Tightlock type originally used on Southern’s Class 375s. Southern’s 375s were all converted to Class 377/3s – these reclassified units can still be identified by their 3-car formation. Note that Southeastern’s 375s (sub-classes 375/3, 375/6, and 375/7) were also converted to Dellner couplers, but not reclassified; its 375/8 and 375/9 units were fitted with Dellner couplers as built.
All units can receive power via third-rail pick-up which provides 750 V DC. There are eight pick-up shoes per unit (twice the number of previous generation 4-car Electric multiple units), and this enables them to ride smoothly over most third-rail gaps. The units in the 377/2, 377/5 and 377/7 sub-classes are dual-voltage, and are fitted with a pantograph to pick up 25 kV AC from overhead lines. On these units the shoe mechanism is air-operated so that when powered down, or working on AC overhead lines, they are raised out of the way. This is used on trains from Milton Keynes to South Croydon which use part of the West Coast Main Line between Milton Keynes and Willesden Junction, and then the West London Line towards Clapham Junction. These trains change to third-rail DC supply on a dual-voltage section of the West London line north of Shepherd’s Bush. Since March 2009, dual-voltage Class 377 sets have also been operating some Thameslink Bedford to Brighton, Rochester and Ashford services. (See below).
Among the remaining units, the trailer coach in each unit has a recess in its roof where a pantograph could be fitted, to allow for future conversion to overhead AC power. Despite most units being DC-only, the class is numbered in the 3xx series normally used for AC units. Video Rating: / 5