The EMD F40PH is equipped with a turbocharged EMD 645E3 V16 cylinder, two-stroke Prime mover. A standard F40PH has a gear ratio of 57:20 allowing a top speed of 103 mph (166 km/h). To support passenger service, the F40PH has another electrical alternator known as the head end power unit.(HEP) The HEP unit generates three-phase AC power at 480 V AC, 750 A or about 500 kW to provide power to the passenger cars for lighting, heating, and air conditioning. Originally F40PHs all powered the HEP alternator from the 16-645E3 prime mover; head end power must be delivered to the train at a constant frequency, so the prime mover had to turn at a constant 900 RPM while supplying head end power (even if the locomotive was standing still with the throttle in Idle). Power to the traction motors was controlled by varying the field excitation of the main (traction) generator. If the HEP was turned on the F40PH ran in Notch 8 all the time. Sitting still or moving at full speed. If the HEP was turned off (while switching perhaps) The prime mover went through the notches like normal. Idle through 8.
Our new F40PH sound is that of an as built F40PH with a shaft driven HEP which can be turned on and off accordingly. It also has Stand-by mode which is used in stations to drop the PM enough that the HEP is still able to be used, yet Fuel savings and noise is more control while not moving. One thing to note is that if 2 F40Ph's were on a train only the engine closest to the cars should have the HEP running.
Many of the F40PH's were rebuilt over the years. If by chance you are modeling a Rebuilt F40PH which may have a Caterpillar HEP unit you should not use this file, but rather the F40PH rebuilt/MP36PH-3C file as it will have the proper sounds and sound schedule for that engine.
