Design of direct current electromechanics converters

The inductor of direct current EEC, usually, is located on stator. Inverted design meet very seldom and are not considered.

On the fig. 1.1 the four-polar inductor of aviation direct current EEC is represented. The inductor consists of steel frame 1, to the inside surface of which basic poles cores 6 are secured by means of screw 3. The basic poles are laminated, that is they are built up of electrical-sheet steel, isolated one from other by the thin lacquer or oxide film. Such design of basic poles assists to Fig. 1.1 reduction of eddy currents energy losses in poles.

On basic poles cores 6exciting winding (EW) coils 2 are located. On the fig. 1.1 these coils are shown on two poles only. Coils2 of all2р poles of inductor are connected in series and form an exciting winding. The inside surface of basic poles tips form a circle which is called stator bore.

In the direct current machines of average and large power not laminated commutating poles 5 are set often between the basic poles 6, windings 9of which are made from wires of large cross section. Windings 9of commutating poles 5are connected in series with the armature winding.

Sometimes together with commutating poles compensative windings are used in direct current machines.These windings are made also of wires of large cross section and they are connected in series with commutating poles and armature windings. The compensative winding 4is placed in slots 7 of basic poles tips. Compensative winding is used in machines which work under trying conditions. The commutating poles and compensative winding are intended for reduction of sparking under brushes and are used in the machines of direct current only. Theend shields are fastened to the frame 1through the screw holes 8.

Often bipolar inductors of low-powered direct current EC are made fully of plates (fig. 1.2). The inductors of micromachine of direct current have not salient poles and make them of the permanent magnets.

In stator bore a laminated package of rotor (armature) is placed, on the outside surface of which the slots are located. In these slots the active wires of armature Fig. 1.2 winding sections are located. At the rotation of armature in the magnetic field created by inductor, electromotive forces (EMF) are induced according to the electromagnetic induction law in the active wires of armature winding sections. The ends and beginning of every section are connected with the plates of collector.

A collector is by the inalienable part of direct current machine. It is a cylinder, which is assembled of the separate copper plates isolated from each other and frame of machine. Beginning and ends of armature winding sections are connected to every plate of collector, thus an end of every given section is a beginning of the following winding section simultaneously.

Thus, two wires are connected to every plate. On the lateral surface of collector the brushes made of the copper-coal, copper-graphite or coal powder by pressing are placed. The brushes are located in the windows of brush holder and pressed to the contact surface of collector by springs. As the brushes wear-out they can move in the windows of brush-holders in the radial direction.

Collector with brushes creates a brush-collector unit which is a mechanical converter of current kind. In speed EMC the brushes are located at the angle to the contact surface of collector (fig. 1.3). Such brush-holder is called reactive. Reactive brush-holder prevents wedging of brush 1 in brush-holder window 2, that assists to the reliable contact of brush with collector, thanks to that tangential component forces of the reaction conditioned by pressure of spring and friction force between collector and brush are balanced.

In the body of brush during its making flexible copper wires (ropes) are pressed. The brushes ropes of one polarity connect by the general busses and feed Fig. 1.3. on the terminal block.

The direct current generators with the parallel excitation are used on the aircraft of civil aviation: ГС-12, ГС-18, СТГ-12, СТГ-18, ГС-24, ВГ-7500.

Abbreviations in the names of generators mean: the "Генератор самолетный", "Стартер-генератор” and generator with possibility of vertical location of shaft. The numbers which are placed after abbreviations indicate nominal powers of generators in kilowatts (kW) or in watts (W).