Twin diesels to power "green" switching locomotive

When it comes to locomotives, the Union Pacific Railroad fleet is considered by many to be the "greenest" in the U.S. railroad industry. In the past five years, 35% of Union Pacific's locomotive fleet has been certified under EPA Tier Zero standards (44% less than the average NOx emission rate of locomotives manufactured prior to the implementation of EPA regulations in 2000) or Tier 1 standards (56% less than the average N[O.sub.x] emission rate of locomotives manufactured prior to the implementation of the EPA rules). Additionally, its 3000 to 4400 hp diesel locomotives that pull heavy-tonnage freight trains over long distances between cities emit only one-third as much N[O.sub.x] compared to over-the-road diesel trucks when measured in emissions per-gross-ton-mile. This can be attributed largely to the greater efficiency of steel wheels on steel rails.

In the future, UP's medium- to heavy-duty switching locomotives used in and around rail yards could also produce less emissions as well as consume less fuel. For instance, UP recently ordered a prototype low emissions switch (LES) locomotive being developed by the National Railway Equipment Co., Dixmoor, Ill. The prototype switcher is based on a system architecture proposed by Newage AVK SEG, the electrical machine unit of Cummins Inc. and NRE Electronics, and uses Cummins QSK19 engines developed for construction equipment The two Cummins inline six-cylinder diesel engines, each with 19 L displacement, will replace the single 1500 hp EMD 12-cylinder 645-series (12-645E) naturally aspirated diesel engine now used in the MP 1500 DC switching locomotive. The locomotive being converted was originally delivered to the former-Southern Pacific Railroad in December 1974.

The two engines each produce a total output of 700 hp, giving the converted switcher locomotive a 1400 hp rating. The engines each produce a massive 1970 lb.ft. peak torque. Peak power for this configuration will be available at 1800 rpm compared to an industry standard 2100 rpm. This results in higher fuel efficiency and reduced noise, the company said. No special modifications from the standard QSK19-C were made for this application.

Like any conventional diesel-electric locomotive, each engine powers a rail specification Newage HC5 generator specifically engineered for this application. These generators power the electric traction motors driving each set of wheels. The converted locomotive will retain its EMD D77 direct current traction motors.

This new switching locomotive is expected to reduce N[O.sub.x] by 70% and particulate matter by approximately 45% from EPA Locomotive Tier 2 levels. Based on the Association of American Railroads (AAR) duty cycle for switching locomotives, it is estimated that as much as a 15% reduction in fuel consumption can be achieved. The LES will offer other advantages with respect to durability and long-term operating costs. The engine will go 30,000 hours between overhaul with an estimated 10-year-plus engine life, according to AAR standards for medium-duty cycle engines. The plug-and-play design for all major components means reduced maintenance downtime.

The LES incorporates advanced electrical equipment, including an ac to dc traction horsepower motor controller/ dc chopper to individually control the amount of power supplied to each traction motor for enhanced adhesion between wheels and track. A low-voltage power supply (LVPS) featuring a 480 Vac to 72 Vdc rectifier/transformer provides up to 10 kW of 72 Vdc electrical power for heating, headlights, ditch lights, and auxiliary lighting, all MU (multiple unit) trail-dine propulsion and operating controls functions and for charging the locomotive's battery.

An auxiliary drive power supply ADPS featuring a 690 Vac to 480 Vac transformer is installed on units equipped with a 690 Vac alternator in order to achieve higher track speeds. This ADPS provides 70 kVA of 480 Vac power for the new air compressor drive and traction motor drive motors plus auxiliary cab accessory power. The NRE Electronics-Microprocessor System (NFORCE) manages and controls all propulsion functions, engine/generator set stop/start functions, alarm and fault logging, operator interface functions and red-time diagnostic monitoring.