Fundamentals of Electricity and Electronics

Direct current (DC) generators convert mechanical energy into electrical energy through electromagnetic induction. Although modern aircraft primarily use alternators, understanding DC generator operation remains important because many aircraft systems and electrical principles are based on generator fundamentals. This article explains the theory of DC voltage generation, the function of commutators and armatures, the effects of … Read more

A DC meter, such as an ammeter, connected in an AC circuit indicates zero, because the meter movements used in a d’Arsonval type movement is restricted to DC. Since the field of a permanent magnet in the d’Arsonval type meter remains constant and in the same direction at all times, the moving coil follows the … Read more

Another important property in AC circuits, besides resistance and inductance, is capacitance. While inductance is represented in a circuit by a coil, capacitance is represented by a capacitor. In its most basic form, the capacitor is constructed of two parallel plates separated by a nonconductor called a dielectric. In an electrical circuit, a capacitor serves … Read more

An amplifier is a device that enables an input signal to control an output signal. The output signal has some or all of the characteristics of the input signal but generally is a greater magnitude than the input signal in terms of voltage, current, or power. Gain is the basic function of all amplifiers. Because … Read more

Magnets are either natural or artificial. Since naturally occurring magnets or lodestones have no practical use, all magnets considered in this post are artificial or manmade. Artificial magnets can be further classified as permanent magnets, which retain their magnetism long after the magnetizing force has been removed, and temporary magnets, which quickly lose most of … Read more

Inspection The following information about the inspection and maintenance of DC generator systems is general in nature because of the large number of differing aircraft generator systems. These procedures are for familiarization only. Always follow the applicable manufacturer’s instructions for a given generator system. In general, the inspection of the generator installed in the aircraft … Read more

The transmission is mounted between the generator and the aircraft engine. Its name denotes that hydraulic oil is used, although some transmissions may use engine oil. Refer to the cutaway view of such a transmission in Figure 1. The input shaft D is driven from the drive shaft on the accessory section of the engine. … Read more

Nickel-Cadmium Batteries Chemistry and Construction Active materials in nickel-cadmium cells (Ni-Cad) are nickel hydrate (NiOOH) in the charged positive plate (Anode) and sponge cadmium (Cd) in the charged negative plate (Cathode). The electrolyte is a potassium hydroxide (KOH) solution in concentration of 20–34 percent by weight pure KOH in distilled water. Sintered nickel-cadmium cells have … Read more

Primary Cell The dry cell is the most common type of primary-cell battery and is similar in its characteristics to that of an electrolytic cell. This type of a battery is basically designed with a metal electrode or graphite rod acting as the cathode (+) terminal, immersed in an electrolytic paste. This electrode/electrolytic build-up is … Read more

Perhaps the most serious trouble in a circuit is a direct short. The term “direct short” describes a situation in which some point in the circuit, where full system voltage is present, comes in direct contact with the ground or return side of the circuit. This establishes a path for current flow that contains no … Read more