The Bombardier ALP-45DP is a type of single cab dual-mode locomotive operated by New Jersey Transit and Exo. The locomotive was designed and originally built by Bombardier until 2021, and by Alstom since 2021.

The ALP-45DP is an electro-diesel locomotive design, based on Bombardier's ALP-46/A and TRAXX locomotives.^{[40][note 3]} Design requirements included weight less than 288,000 lb (131,000 kg), length less than 75 ft (22.86 m), and EPA-compliant emissions.^[23]

The challenge of fitting diesel and electric systems within the same carbody while staying within axle load limits, led to the choice of two high-speed, twelve-cylinder Caterpillar 3512C HD diesel engines rated at 2,100 hp (1.6 MW) each.^[23] The systems for the two engines are independent – for example, each has a separate 3,400 L (750 imp gal; 900 US gal) fuel supply (split across four total tanks owing to NJT regulations regarding tunnel operations that limit individual fuel tank capacity to 400 US gal (1,500 L; 330 imp gal)^[19]) – allowing the locomotive to operate on one engine in case of failure or under low load. The engines are capable of shorter startup times from idle to load (100 rpm/s) than traditional medium speed diesel engines.^[41] To achieve mass balance and distribution within the locomotive, the engines are situated on either side of the transformer, which is located in the center of the locomotive.^[24] The engines are manufactured in Lafayette, Indiana, USA.^[5]

When running under diesel power, each engine powers a MITRAC TG 3800 A alternator having an output of 1700 kVA @ 1800 rpm.^[9] Power output is reduced from 6,700 hp (5.0 MW) (including HEP) in electric mode to 4,200 hp (3.1 MW) in diesel mode;^[23] under diesel power, the same tractive effort curve is maintained up to around 25 km/h (16 mph) (assuming 2,734 hp (2.039 MW) available for traction after HEP reductions for an 8 car train).^[42][11]

The pantograph is of TransTech design.^[43] The ABB main transformer has four secondary taps, switchable to supply 1360 V under all electrification supplies. There are two MITRAC TC 3360 DP V01 DC-AC main converters,^[44] one per bogie, which convert the single phase input to a 2,8 kV intermediate DC-bus, using IGBT based switches. Each DC bus powers two traction converters, with each traction inverter powering a separate traction motor.^[45][46] The locomotive uses four 1,300 kW (1,700 hp) MITRAC DR 3700 F^{[note 1]} fully suspended, bogie mounted traction drives to reduce unsprung mass.^[48][49][43]

In addition to taps for the traction inverters, the locomotive transformer supplies 1 100 kVA and 140 kVA for head-end power and locomotive auxiliary power.^[46] Two partially-redundant auxiliary inverters are incorporated into the two main converter units.^[45][50] Normally, one provides a 3 phase, 480 V 60 Hz 1100 kVA supply for head end power, while the other provides several 3 phase variable voltage, variable frequency supplies (up to 480 V 60 Hz) for the traction motor fans, transformer fans, and inverter cooling circuit motors.^[50] In the event of a converter failure, it is possible to route all supply through a single converter, ensuring redundancy and margin of error operations. ^[51]

HEP is maintained when changing power modes, due to the fact that the pantograph is not lowered until the prime movers have been started (when changing from electric to diesel), and the prime movers are not shut down until the pantograph has made contact with the catenary wire (when changing from diesel to electric). In either case, the changeover takes approximately 100 seconds.^[43] The locomotive is capable of performing a mode change while on the move; however, NJ Transit has reprogrammed their locomotives to only allow a mode change during a station stop. This is most likely to prevent the loss of power during the transition to diesel mode with a limited amount of wire left.

The braking system uses Wabtec's Fastbrake control system, with two disc brakes per axle.^[52] The mechanical parts of the brake system were supplied by Faiveley Transport.^[53] Compressed air supply is charged through a Knorr screw compressor with a capacity of 3,400 L/min (750 imp gal/min; 900 US gal/min) at 10 bar (1,000 kPa; 150 psi) pressure,^[54] stored in two 480 L (110 imp gal; 130 US gal) air reservoirs.^[52] The dynamic and regenerative braking system operates under all three NJT electrical systems.^[9] In addition, the locomotive, while in diesel mode, is capable of routing power generated by the electric brake to HEP and locomotive auxiliary power requirements in addition to the dynamic brake resistor.^[55]

The locomotives are within Amtrak's A-05-1355 structure gauge and meet CFR and AAR crashworthiness standards.^[43] The diesel engines meet Tier 3 EPA emission standards, and work is being done to enable an upgrade to Tier 4 standards, which took effect on January 1, 2015.^[56] Total length is 21.8 m (72 ft), approximately 2 m (6 ft 7 in) longer than the ALP-46A.^[24]

The bodyshells of the locomotive were constructed at Bombardier's Wrocław site, the bogies at Siegen, and the alternators at Hennigsdorf factory. The locomotives were assembled at Kassel.^[57]

• ALP-45DP at Innotrans 2010
• Front view
• Rear corner view
• Frontal shot
• Pantograph mounted at the rear of the locomotive
• Bogie and suspension detail
• Caterpillar prime mover inside the engine room
• Cab interior
• Engineer's controls