AC Alternators in Modern Aircraft

An alternator is an electrical generator that converts energy into electricity in the form of an alternating current (AC).  An automatic drive controls the alternators rational speed allowing for the alternator to maintain a constant output. All AC alternators are required to rotate at a specific speed to keep the frequency of the AC voltage within proper limits. If a frequency strays more than 10 percent from the required value, the electrical system will not work properly. To ensure an alternator always stays within values, a unit called a constant-speed drive is used. This unit always rotates at the correct speed and can be mounted independently or within the alternator housing. This unit is comparable to an automatic transmission found in an automobile; the engine can change but the speed remains constant.  In an aircraft, the hydraulic transmission is mounted between the AC alternator and the engine. Hydraulic oil is used to operate the transmission allowing for a constant output speed and engine rpm drives the hydraulic pump, turning the alternator.

Modern aircraft use AC alternators powered by several computerized control units located in the aircraft’s equipment bay.  Since commercial aircrafts carry hundreds, even thousands, of passengers daily, the systems have special reinforcements in case of system failure. The special reinforcement, or backup system, typically consists of a bus power control unit or a generator. Without these units, plane failure could happen very easily, putting all passengers and aircraft crew at risk. Alternators are crucial to the function of aircrafts, so it is important to make sure every piece is functioning properly with routine maintenance and repair.

ASAP NSN Parts, owned and operated by ASAP Semiconductor, should always be your first and only stop for all your alternator spare parts. ASAP NSN Parts is a premier supplier of AC alternators and electronic circuits. Whether new, old or hard to find, we can help you find the parts you need. ASAP NSN Parts has a wide selection of parts to choose from and is fully equipped with a friendly and knowledgeable staff, so you can always find what you’re looking for, 24/7x365. If you’re interested in a quick and competitive quote, email us at or call us at +1-714-705-4780. 


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