By Rowan BellGraduate Electrical Engineer,

Interfleet Technology Ltd

An Overview of the Electrical Design Process of Interfleet

Technology’s IMechE Railway Challenge 2012 Winning

Locomotive

Railway Engineers Forum Scotland, Young Railway Professionals’

Presentation Competition

Glasgow, 21st November 2012

The Challenge comprised of three tests for the

locos:

Traction

A time trial between two points, limited to

10km/h, with penalties for speeding!

• Acceleration• Deceleration• Speed control

10km/h

T

ω

Energy Recovery& Reuse

A test of regenerative braking efficiency

regen

regen fwd

rev

The IMechE Railway Challenge

• A competition to design, build and trial a 10¼’’ gauge locomotive

• Open to universities and companies of the railway industry

• Loco to be refuelled within 90s, and meet emergency braking and gauging

specs

Ride Comfort

A test to quantify the movement and

vibration of a loco’s bodyshell during

motion

ITL’s Design Process: My Contribution

• Boundaries of the specifications, mechanical requirements and our timescales

were tight!

• An ICE prime mover and an electrical traction system were both required..

Electrical Traction System

The regenerative

braking function?

EnergyStorage

2Q or 4Q, BLDC, inductionmotor or PMSM drive?

Li+ batteries

Brushed DCmotors with 1Q

controller

Regenerative Braking and

Traction Facility...

Supercapacitors

compact economical proven!

feasible challenging!

high power lightweight safe eco?

Options:

Aux.

Generator

ElectricalTraction System

Rail

Energy Storage

?

RegenerativeBraking and

Traction Facility

Power Scheme:

The Topology

Traction power

Regenerative braking power

Regen. energy traction power

Auxiliaries’ power

Armature Voltage Feedback signal

User interface signals

AC-DC convert

er24V, 8A o/p

4 Electromagnetic

Disc Brakes

Control Relays, Interlock Relays

&Safety Features

Petrol Generator 110V / 230V,

50Hz, 13A o/ps

1Q DC Motor

Controller 90V, 32A

o/p

4 Brushed

DC Motors

in series24V, 28A

Regenerative Braking and

Traction Facility with supercapacitor

bank..

• The loco employs the following electrical topology:

Regenerative Braking and Traction Facility (1)

• Falling generated voltage + supercapacitors’ charging curve + ? = practical

deceleration..

• Supercapacitors’ discharge curve + rising Back EMF + ? = practical

acceleration..

• Two variable-output DC-DC converters in anti-parallel?

• The driver would control braking and traction by changing the Output Voltage

demand..

Traction converter(Flyback)

Braking converter(Flyback)4

Brushed DC

Motors in series

24V, 28A

Supercapacitor bank(with series inductance)

Output Voltage

Output Voltage

Regenerative braking power Regen. energy traction

power

User interface

signals

Regenerative Braking and Traction Facility (2)

• For braking, the solution was to employ PWM of the generated voltage..

• The motors may be configured in series or parallel

• For traction, the supercapacitors are simply switched onto the motors, configured

in parallel

• The PWM time period was to be calibrated during testing

Generated

voltage

Added series

inductance

4 x supercapacito

rs, 30,443J

PWM

58F, 16.2V supercapacitor

ITL’s Performance and Success

• ITL’s loco came first in all three tests!

• Ride Comfort was excellent!

• Traction was good!

• Energy Recover & Reuse wasn’t great..

The braking effort was huge, and the starting torque was really small..

That 4Q motor controller is looking pretty good!

BO O M !

Thank you!