Armature winding

The potential differenee aeross the armature winding is therefore... 

For the d.e. motor shown in Figure 4.14, the potential differenee aeross the armature winding is given by equation (4.21)... 

Anker, m. anchor (Elec.) armature, rotor, -spannung, /. (Elec.) armature voltage, -spule, /. (Elec.) armature coil, -strom, m. (Elec.) armature current. -wicklung, /. armature winding. 

Direct-current motors are classified as separately excited motors, series motors, shunt motors, and compound motors. The field winding of a separately excited motor is in a circuit that is energized by a separate dc source the field winding is not physically connected to the armature circuit (containing the armature winding). 

The common connection of all three armature windings in the Y connection allows a fourth, or neutral, conductor to be used. This neutral point is often grounded in transmission and distribution circuits. Such a circuit is termed a three-phase, four-wire circuit. 

If a variable speed is to be provided with this type of stirrer drive, a motor in which the current is passed through the armature winding is required, and this in turn requires that the motor have brushes. This requirement is of little consequence in most applications, but if the... 

To reverse the direction of rotation of a direct-current motor, reverse the terminals to either the field or the armature winding not to both. 

It is a particular characteristic in the solution of differential equations involving resistances and inductances that a DC component accompanies the symmetrical AC component. The magnitude of the DC component can equal that of the peak AC component since both are determined by X J. The decay of the DC component can be reasonably slow and is determined by which is a function of X J and the armature winding resistance Ra With machines that have significant values of X J and particularly low values of R, the value of Ta can become relatively high. When Ta is high in relation to Tj and rj it is possible that the initial AC decay is faster than the DC decay. When this happens the AC instantaneous current does not reach zero until several cycles have passed. This puts an extra strain on the circuit breaker and can cause problems at the point when it starts to open to clear the fault current. 

ARMATURE BACK AMPERE TURNS - The magnetic field produced by current flowing in the armature winding, that opposes and reduces the number of magnetic lines of force, produced by the field magnets of a motor or generator. 

ARMATURE TESTER - Any device used for locating faults or defects in the armature winding. 

ARMATURE VARNISH - Is a liquid put on the field and armature windings, to improve the insulation of the cotton covering on the wires. 

ARMATURE WINDING - All of the copper wire placed on the armature, and through which the current flows. 

Practical motors are constructed as shown in Fig. 2.46. All d.c. motors contain a field winding wound on pole pieces attached to a steel yoke. The armature winding rotates between the poles and is connected to the commutator. 

Contact with the external circuit is made through carbon brushes rubbing on the commutator segments. Direct current motors are classified by the way in which the field and armature windings are connected, which may be in series or in parallel. 

The field and armature windings are connected in series and consequently share the same current. The series motor has the characteristics of a high starting torque but a speed which varies with load. Figure 2.47 shows series motor connections and characteristics. For this reason the motor is only suitable for direct coupling to a load, except in very small motors, such as vacuum cleaners and hand drills, and is ideally suited for applications where the machine must start on load, such as electric trains, cranes and hoists. 

Reversal of rotation may be achieved by reversing the connections of either the field or armature windings but not both. This characteristic means that the machine will run on both a.c. or d.c. and is, therefore, sometimes referred to as a universal motor. 

Practical motors are constructed as shown in Fig. 10.14. All d.c. motors contain a field winding wound on pole pieces attached to a steel yoke. The armature winding rotates between the poles and is connected to the commutator. Contact with the external circuit is made through carbon brushes rubbing on the commutator segments. Direct current motors are classified by the way in which the field and armature windings are connected, which may be in series or in parallel. 

The field and armature windings are connected in series and consequently share the same current. The series motor has the characteristics of a high starting torque but a speed which varies with load. Figure 10.15 shows... 

Coils, transformers, field and armature windings, metal castings, and sealing of porous structures. 

The crankshaft extends directly to an alternator, which consists of two main setsof windings-coils of insulated copper wire wound closely around an iron core. One set, called stator windings, is in a fixed position and shaped like a broad ring. The other set, the armature windings, is wound on the rotor which is fixed to the rotating crankshaft. The rotor makes about 3,000 revolutions per minute. 

Speed can be controlled either by the voltage across the armature winding or by varying the field current... 

Core An element of magnetic material, serving as part of a path for magnetic flux. In rotating machines, this is frequently part of the stator, a hollow cylinder of laminated magnetic steel, slotted on the inner surface for the purpose of containing the armature windings. Exciter The soirrce of all or part of the dc field current for the excitation of an electric machine. 

The simplified drawing of an armature winding in Fig. 6.31 shows a single phase only. All generators except those with very small ratings have three phases, each phase consisting of several condnctors. 

Temperature rise in the windings and insulation due to losses. This includes losses due to excitation cnrrent in the field windings, ac current in the armature windings, the magnetic circuit, and any stray currents or magnetic fields that are generated. 

Impregnation Results in complete coverage of intricate and closely spaced parts. Seals fine leaks or pores. Requires vacuum or pressure cycling or both. Spe- Coils, transformers, field and armature windings, cial equipment usually required. metal castings, and sealing of porous structures. ... 

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