š Key Concepts
ā¢ Synchronous motor excitation levels (under-excited, normally-excited, over-excited) and how they affect power factor
ā¢ Difference between lagging and leading power factor and what type of reactive power (inductive vs capacitive) they represent
ā¢ How a synchronous motor can be used to correct an overall plant power factor
š Think About
ā¢ Ask yourself: when the plant has a lagging power factor, do you need the synchronous motor to behave more like an inductive or capacitive element to correct it?
ā¢ Think about what happens at unity power factor for a synchronous motor: is its excitation low, normal, or high compared to that condition?
ā¢ Match each excitation condition (under, normal, over) to whether the motor draws or supplies reactive power, then see which option lines up logically.
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Before You Answer
ā¢ Be clear which condition (under-excited, normally-excited, over-excited) corresponds to the motor supplying reactive power to the system versus absorbing it.
ā¢ Verify the relationship: lagging power factor ā inductive load, leading power factor ā capacitive load.
ā¢ Check which plant condition (lagging, leading, or unity) is associated with the motor running at normal excitation (i.e., not strongly correcting in either direction).