Passenger Locomotive

Overview

A passenger locomotive is a single traction unit built to haul express coaching stock at high speed rather than to move heavy slow freight. This machine takes its energy from a 25 kV 50 Hz overhead line, steps the voltage down in an onboard transformer, and turns four asynchronous motors through power-electronic converters. The four motors sit on two Bo-Bo Motor Bogie units in a Bo-Bo arrangement, where every axle is driven, and the final drives use a high gear ratio so the wheels can turn fast enough for 200 km/h while the motors stay within their rated speed. The whole machine sits inside the Carbody Shell and rides on the bogies, with roughly 9,000 Fastener Set groups holding the structure and equipment together.

Power enters through the Pantograph and the HV Roof Equipment, passes down to the Main Traction Transformer, and is processed by two Traction Converter units. Braking is handled by the Brake System, the train coaches are fed from the Head-End Power Supply, and the driver works from the Driving Cab under the supervision of the Control Electronics. Heat from the transformer and converters is rejected by the Cooling System, and the Auxiliary Systems add lights, horns, sanders and the control battery.

Current collection and high-voltage path

The Pantograph presses a carbon Carbon Contact Strip against the contact wire with a regulated force near 70 N, held up by the Raising Air Bellows and insulated from the roof by Roof Support Insulator posts. From the pantograph the line voltage runs through the Main Vacuum Circuit Breaker, which can interrupt fault currents, past the Surge Arrester that clamps lightning and switching overvoltages, and along the HV Roof Busbar to the transformer bushing. The Primary Current Transformer measures line current for protection and energy metering, and the Earthing Switch grounds the roof for safe maintenance.

Transformer and traction converters

Because the supply is single-phase 25 kV, the locomotive cannot use it directly. The Main Traction Transformer hangs under the floor in an oil bath and steps the line down across a grain-oriented Laminated Core to several secondary windings, with Transformer Oil Pump units forcing oil through the Transformer Tank for cooling. Each secondary feeds a Traction Converter. The Four-Quadrant Line Converter is a four-quadrant rectifier that draws current at almost unity power factor and, during braking, pushes regenerated energy back to the catenary. It charges a DC link, smoothed by the DC Link Choke and DC-Link Capacitor banks, from which two Motor-Side Inverter stages synthesise variable-frequency three-phase current for the motors. The IGBT stacks are clamped to Liquid Cooling Plate cold plates in the water-glycol loop.

Bogies and running gear

Each Bo-Bo Motor Bogie is a welded H-frame carrying two Traction Motor (AC) units of about 1.4 MW. The motor turns a Final Drive Gear Unit whose single helical stage uses a ratio chosen for top speed, then drives the Wheelset. The wheelset combines a forged 34CrMo4 Hollow Axle, two 1,250 mm Monobloc Wheel forgings, and the Axle Brake Disc pair, riding on Axlebox bearings. Suspension is in two stages: steel Primary Suspension Spring coils between axlebox and frame, and rolling-lobe Secondary Air Spring air springs between frame and body for ride levelling. The Yaw Damper units suppress the bogie hunting that would otherwise grow unstable at high speed, and the Traction Rod Linkage passes drive and braking forces into the carbody at axle height.

Braking and head-end power

The Brake System blends three methods. Regenerative braking through the traction converters does most of the work and returns energy to the line. When that is not enough, the Brake Control Unit adds friction braking through the Disc Brake Caliper units on the axle discs, supplied with air by the Air Compressor and stored in the Main Air Reservoir tanks. For emergency stops the Magnetic Track Brake magnets drop onto the rail. A passenger locomotive also has to power its train: the Head-End Power Supply takes a transformer winding and produces a regulated hotel-power bus near 1,500 V through the HEP Converter, feeding coach heating, air conditioning and lighting through the Trainline Jumper Cable cables.

Cab, control and signalling

The driver sits in the single Driving Cab at the Driver Desk, commanding effort with the Power/Brake Controller and direction with the Reverser Switch. Vigilance is enforced by the Vigilance Pedal. The Control Electronics are built around the Train Control Computer, which coordinates traction, braking and auxiliaries over the train bus, and the ETCS Onboard Unit, which reads trackside balises through the Balise Antenna and enforces the movement authority using Odometry Sensor data. Both present information to the driver on the Driver Display. Heat from all of this electronics is carried away by the Cooling System, whose Cooling Fan units pull air through roof radiators, while the Auxiliary Systems keep the headlights, horns and sanders working from the Auxiliary Converter and the control battery.