Leece-Neville Generator (Operation)

Electrical System Component Repair
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(2) If the output voltage of the generator is higher than the zener

reference voltage, it causes a transistor to turn ON which reduces the exciter

field current. This brings the output voltage down.

(3) If the output voltage of the generator is lower than the zener

reference voltage, it causes a transistor to turn OFF which increases the exciter

field current. This brings the output voltage up since the magnetic flux in the

rotor is increased.

10. LEECE-NEVILLE GENERATOR (OPERATION).

a. Basically, there are three components to be considered in the operation

of the AC charging system: the AC generator, diode rectifier, and transistor

regulator (fig 38). The AC generator is of the revolving field type (the rotor is

the field) so that only two sliprings are needed. The sliprings and brushes are

required to carry only low amperage current to control the exciter field winding

flux on the rotor.

Figure 38.

Block diagram of AC charging system.

(1) The higher the exciter field winding current, the higher the flux

and the higher the three-phase (3) output current and voltage.

(2) If the exciter field winding current is low, this will lower the

three-phase (3) output current and voltage.

b. The six diode rectifiers change the three-phase (3) AC voltage into DC

voltage. This is accomplished by means of silicon diodes that permit the passage

of current in one direction only.

(1) The current capacity is controlled by parallel paths into the

regulator circuit that supplies the exciter field winding with current.

(2) With only one of the paths connected, the current output will have a

40-ampere capability.

(3) With both paths connected to the regulator more current is available

to the field winding through the regulator with a maximum of 60 amperes at the DC

output.

OS 010, 1-P20