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In land vehicles with high-power electrical loads, other than the low-voltage DC bus (14V, 28V, or 42V) for the low-power conventional loads, a high-voltage bus, e.g., 200V DC, is required for high-power loads such as hotel loads and electrically-assisted propulsion systems. In addition, some advanced electrical loads including luxury loads and AC power point require 120V, 60Hz AC voltage. These land vehicles include heavy duty, fire fighting, and military vehicles. There are two traditional approaches in obtaining a dual DC voltage bus system. The first one is to obtain the low-voltage DC from the alternator and boost it to the high-voltage DC. The second method is to obtain the high-voltage DC directly from the alternator and reduce it to the low-voltage. Both approaches require additional step-up or step-down power conversion stages, which inherently result in a reduced efficiency. In this paper, a new approach with a 28V/200V dual voltage alternator is considered.

A new, enclosed brushless alternator is developed for use in either hazardous or contaminated environments which can produce 50 Amps at 28 Volts DC. The fully enclosed design of this alternator allows it to work in environments which contain corrosive agents, metallic particulates, or volatile media. The brushless design of this unit in conjunction with the enclosure makes this alternator virtually maintenance free.

A dual-voltage alternator is a single alternator which produces two simultaneous and independently regulated electrical outputs, as shown in Fig. 1. This means that a vehicle with a single dual voltage alternator will be capable of powering, simultaneously, both the standard vehicle 12 volt electrical system (which powers lights, horn, instruments) and also to power another electrical system at a different voltage. The other, or secondary electrical system, is typically a higher voltage system. It may be a 24 volt electrical system to power military communications equipment, or it may be a 48 volt electrical system to provide power for other vehicle electrical power needs, such as electrical heaters for engine emission control. This paper describes a dual-voltage alternator design for automotive applications.