£7m refit speeds train on its way

Project also included interior redesign and engineering work on a four-car set of Bombardier Class 317 rolling stock

Class 317: Switch from DC to AC comes with regenerative braking

Angel Trains has created a “new train from old” after carrying out £7 million worth of improvements on a four-car set of Bombardier Class 317 rolling stock. Re-tractioning work has resulted in the completion of a pre-series demonstrator with an AC rather than DC power unit which enables the train to make use of regenerative braking and to accelerate faster.

The project also included an interior redesign and engineering work on the doors to improve reliability and make maintenance easier.

Malcolm Brown, Angel Trains’ chief executive, said: “It gave us a fantastic opportunity to develop a new train from old. We are now going to test it on the passenger network.”

Kate Marjoribanks, engineering director at train operator Abellio Greater Anglia, which uses Class 317s, said she was keen to see the train perform on the network. She said: “The 317 fleet is the mainstay of the West Anglian route. We use it to operate 300 services a day.”

The current configuration of the Class 317 consists of one motor car and three trailers, with the motor car housing the traction and high-voltage equipment. The roof-mounted pantograph and high-voltage circuitbreaker are connected to the underframe-mounted transformer via the HT cable. The wheelsets are powered by four axle-hung DC traction motors, which are controlled by solid-state thyristors that vary the voltage supply to the motors and convert the current from AC to DC.

Re-traction was performed by removing the DC motors and replacing them with new AC traction motors fitted to the existing gearboxes. The phase-controlled converters for the DC motors have been replaced with AC converters feeding the asynchronous AC traction motors. The existing transformer has been retained and inductors have been connected between the transformer secondary windings and the line converter. 

A new voltage measurement transformer has been added to the roof to provide the propulsion equipment with information about the line voltage.