These are the various types of head end power systems that Northwest Rail Electric has been involved with:
Amtrak style HEP consists of twelve #4/0 wires running from one end of the car to the other. Power is 480 volts three phase, operating in 4 parallel sets. System capacity is approximately 1,200 kW. The end of each car is equipped with four HEP connectors: two fixed jumpers with cables, and two receptacles for the jumpers to connect to. There can be only one generator that feeds a set of cars. If two generators are used, then there must be some sort of electrical isolation between the two systems, such as one generator operating one set of cars, and the other operating another set of cars. It is possible for two or more generators to be in the same generator car and operate as parallel units in the same power plant. Each car has a HEP junction box where the 4 sets of wires join, in order to even out the electrical load between the cable sets.
We have a list of the parts required to convert a typical passenger car to Amtrak compatible HEP.
In this HEP system, which has also been used in the USA on some operations, the basic connection and wire scheme are the same as in Amtrak style HEP. It consists of twelve #4/0 wires running from one end of the car to the other. Power is 480 volts three phase. However, the wires on the left and right side of the cars do not connect. They only tie together at the generator, if they do so there. The cars have an electrical system that allows selection between HEP A and HEP B. System capacity is approximately 1,200 kW. The end of each car is equipped with four HEP connectors - two fixed jumpers with cables, and two receptacles for those cables to plug into. Two generators can be used: one powering the A HEP system, and the other powering the B HEP system. In true Western Canadian HEP, at one end of the cars HEP A and HEP B cross sides, to allow for better load balance. Some adaptations of this system do not have the HEP system cross over, but true Western Canadian style does. There are two HEP junction boxes on each car.
Half HEP is one-half of the Western Canadian style system, in many cases only running down one side of the cars. If the HEP only runs down one side of the cars it means that the cars can not be turned independently, or the HEP lines will not be able to be connected. It consists of six #4/0 wires running from one end of the car to the other, operating in two parallel sets. Power is 480 volts three phase. System capacity is approximately 600 kW. The end of each car is equipped with two HEP connectors, usually one fixed jumper with cables, and one receptacle.
In one adaptation of this system we have seen, the the six #4/0 wires are replaced with three 535 MCM wires, and the connectors are spliced together at each end of the car to each end of these cables. This still gives the capacity of the HEP system about 600kW.
In this system, there is only one set of three #4/0 wires through the car, with the system still being 480 volt three phase. In many cases, there are only two HEP receptacles only on each car: one at each end. In that case, the HEP line is run down one side of the car. The system capacity is about 300kW.
In some cases, the cars have two sets of HEP receptacles on each end, with the connectors spliced together at each end of the wires that run the length of the car. This allows for one HEP receptacle on each side of each end of the car. This means that the cars can be turned independently and still have the HEP lines connected.
However, unless the cars are operating with an existing fleet of 575 volt HEP equipment, Don't Use This System! It is too limiting when trying to interchange cars with the rest of the passenger car fleet in North America. 480 volt equipment is far more common in North America, and it would be best to be compatible with the vast majority of passenger cars in service.
The load required to operate these cars depends on the amount of heating and air conditioning required, the amount of dehumidification required, and the activity inside the car. Obviously, if the dining car is preparing dinner with the kitchen in full operation it will have a lot greater electrical load than if it is simply being used as added seating capacity at the tables.