By Rowan Bell Graduate 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, 21 st November 2012

The Challenge comprised of three tests for the locos : Traction A time trial between two points, limited to 10 km / h, with penalties for speeding ! Acceleration Deceleration Speed control 10 km/h T ω Energy Recovery & Reuse A test of regenerative braking efficiency regen fwd rev The IMechE Railway Challenge A competition to design, build and trial a 10 ¼’’ gauge locomotive Open to universities and companies of the railway industry Loco to be refuelled within 90 s, 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 ? Energy Storage 2 Q or 4 Q, BLDC, induction motor or PMSM drive ? Li + batteries Brushed DC motors with 1 Q controller Regenerative Braking and Traction Facility... Supercapacitors compact economical proven ! feasible challenging ! high power lightweight safe eco ? Options : Aux. Generator Electrical Traction System Rail Energy Storage ? ? Regenerative Braking 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 converter 24 V, 8 A o / p 4 Electromagnetic Disc Brakes Control Relays, Interlock Relays & Safety Features Petrol Generator 110 V / 230 V, 50 Hz, 13 A o / ps 1 Q DC Motor Controller 90 V, 32 A o / p 4 Brushed DC Motors in series 24 V, 28 A 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 24 V, 28 A Supercapacito r bank ( with series inductance ) Output Voltage Regenerative braking powerRegen. 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 Generate d voltage Added series inductance 4 x supercapacitor s, 30,443 J PWM 58 F, 16.2 V 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 4 Q motor controller is looking pretty good !

Thank you !