Question 111Electricity/Electronics - 1st Asst/Chief70% to pass
When a self-excited alternator's field has lost its residual magnetism due to a prolonged idle period, it will fail to produce a voltage. Flashing the field is the procedure used to restore the residual magnetism. Using a 12 volt storage battery, how is this performed?
AI Explanation
The correct answer is B.
To restore the residual magnetism of a self-excited alternator's field that has lost it due to a prolonged idle period, the field must be "flashed" using a 12-volt battery. This is done by disconnecting the F+ and F- leads from the alternator field, then connecting the F+ lead to the positive terminal of the battery and the F- lead to the negative terminal. This allows a current to flow through the field windings, which re-magnetizes the field and restores the residual magnetism.
The other options are incorrect because they either disconnect the wrong leads (the stator leads instead of the field leads) or connect the leads to the wrong battery terminals, which would not properly flash the field and restore the residual magnetism.
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#109 As shown in figure "B" of the illustration, what is the purpose of the synchronous compensator? Illustration EL-0133 #110 Two AC generators of the same capacity are operating in parallel. One with a zero speed droop setting and the other with a 5% speed droop. If its capacity is not exceeded, what will be the characteristic of the unit whose governor has the zero speed droop setting? #112 If it becomes absolutely necessary to run an alternator at lower than 5% below its rated frequency, in terms of output voltage, what must be done? #113 Upon loss of field excitation of a generator operating in parallel with others, what must be done? #114 When a self-excited DC generator's field has lost its residual magnetism due to a prolonged idle period, it will fail to produce a voltage. Flashing the field is the procedure used to restore the residual magnetism. Using a 12 volt storage battery, how is this performed?