Railway Engineers Forum Scotland, Young Railway Professionals’ Presentation Competition Glasgow, 21st November 2012 An Overview of the Electrical Design Process of Interfleet Technology’s IMechE Railway Challenge 2012 Winning Locomotive By Rowan Bell Graduate Electrical Engineer, Interfleet Technology Ltd 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 The Challenge comprised of three tests for the locos: 10 Traction Ride Comfort A time trial between two points, limited to 10km/h, with penalties for speeding! A test to quantify the movement and vibration of a loco’s bodyshell during motion km/h • Acceleration • Deceleration • Speed control Energy Recovery & Reuse A test of regenerative braking efficiency T regen fwd ω rev regen 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.. Power Scheme: Options: Electrical Traction System Generator The regenerative braking function? Energy Storage 2Q or 4Q, BLDC, induction motor or PMSM drive? Aux. Electrical Traction System Energy Storage ? Regenerative Braking and Traction Facility Rail Brushed DC motors with 1Q controller compact economical proven! Regenerative Braking and Traction Facility... feasible challenging! Li+ batteries Supercapacitors high power lightweight safe eco? The Topology • The loco employs the following electrical topology: Petrol Generator 1Q DC Motor Controller 90V, 32A o/p 4 Brushed DC Motors in series 24V, 28A Regenerative Braking and Traction Facility with supercapacitor bank.. 110V / 230V, 50Hz, 13A o/ps AC-DC converter 24V, 8A o/p Traction power Regenerative braking power Regen. energy traction power 4 Electromagnetic Disc Brakes Control Relays, Interlock Relays & Safety Features Auxiliaries’ power Armature Voltage Feedback signal User interface signals 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? 4 Brushed DC Motors in series 24V, 28A Braking converter (Flyback) Output Voltage Output Voltage Traction converter (Flyback) Supercapacitor bank (with series inductance) • The driver would control braking and traction by changing the Output Voltage demand.. 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 Added series inductance Generated voltage 4 x supercapacitors, 30,443J PWM 58F, 16.2V supercapacitor • For traction, the supercapacitors are simply switched onto the motors, configured in parallel • The PWM time period was to be calibrated during testing 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! Thank you!