When AC generators are paralleled, what component ensures constant frequency?

• A. CSD
• B. Governor
• C. Synchronizer
• D. Inverter

Answer: (A)

In parallel AC generation, keeping the output frequency steady is achieved by maintaining the generator operating at a fixed speed regardless of engine RPM. The constant speed drive unit does exactly that: it decouples the generator’s speed from the engine and keeps the generator running at its rated speed so the electrical frequency stays constant as loads change. The governor controls engine speed, but it’s the constant speed drive that directly preserves the generator’s frequency. Synchronizers are used to align phase and frequency before paralleling but don’t set the frequency themselves, and an inverter isn’t involved in maintaining the generator’s frequency in this setup.