NEIEP Mechanics Practice Exam

If the generator is rotating and you apply voltage to the field but no armature voltage is produced, what is most likely wrong?

1. The generator field is open

2. The armature is burnt out

3. The voltage regulator is malfunctioning

4. The generator is overloaded

The correct answer is: The generator field is open

When a generator is rotating and you apply voltage to the field but no armature voltage is produced, this situation typically indicates an issue with the field circuit. Specifically, if the generator field is open, that means there is a break in the electrical path of the field winding, which prevents the creation of a magnetic field necessary for generating voltage in the armature winding. Without a magnetic field, the armature will not induce any voltage, even with the generator in motion and voltage applied to the field windings. Therefore, the absence of armature voltage in this scenario strongly points towards the condition of the generator field. In contrast, if the armature were burnt out, there might be physical damage causing the lack of voltage, but the question specifically points to applying voltage to the field. Issues with the voltage regulator generally involve improper voltage levels, but the scenario does not suggest that the generator is functioning at all. Overloading of the generator would typically manifest through overheating or performance issues while still allowing voltage to be produced, so it does not apply here.