🔍 Key Concepts
• Synchronous motor excitation levels (under-excited, normally-excited, over-excited) and how they affect power factor
• Difference between lagging and leading power factor and what type of reactive power (inductive vs capacitive) they represent
• How a synchronous motor can be used to correct an overall plant power factor
💭 Think About
• 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?
• Think about what happens at unity power factor for a synchronous motor: is its excitation low, normal, or high compared to that condition?
• Match each excitation condition (under, normal, over) to whether the motor draws or supplies reactive power, then see which option lines up logically.
✅ Before You Answer
• Be clear which condition (under-excited, normally-excited, over-excited) corresponds to the motor supplying reactive power to the system versus absorbing it.
• Verify the relationship: lagging power factor ↔ inductive load, leading power factor ↔ capacitive load.
• 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).