Lincoln Electric 200 service manual DC Generator Machines, Figure E.7 DC Generator Theory

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E-7	THEORY OF OPERATION	E-7
	FIGURE E.7 — DC GENERATOR THEORY

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MECHANICAL COUPLING

F	C
	U
I	R
E	R
L	E
D	N
	T
SHUNT FIELD WINDINGS
MAGNETIC FIELD	DC CURRENT
GENERATOR	BRUSH
	ARMATURE
	SHAFT
ARMATURE	BRUSH
MAGNETIC FIELD	DC CURRENT
SHUNT FIELD WINDINGS
F	C
	U
I	R
E	R
L	E
D	N
	T

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DC GENERATOR MACHINES

The armature winding of a DC generator is located on the rotating member. Current is conducted from it by means of carbon brushes. The field winding is located in the stator, which is stationary and excited by direct current.

The armature coil sides are placed at opposite points on the rotating shaft with the conductors parallel to the shaft. The armature assembly is normally turned at a constant speed by a source of mechanical power con- nected to the shaft. When the armature rotates through the magnetic field produced by the stationary field winding, it induces a coil voltage in the armature winding. The voltage induced in an individual armature coil is an alternating (AC) voltage, which must be recti- fied. In a conventional DC generator machine, rectifi- cation is provided mechanically by means of a commu- tator. A commutator is a cylinder formed of copper seg- ments insulated from each other and mounted on, but insulated from, the rotating shaft. Stationary carbon brushes held against the commutator surface connect the armature windings to external terminals. The com- mutator provides full-wave rectification, transforming the voltage waveform between brushes and making available a DC voltage to the external circuit.

PIPELINER® 200