Polyphase (three-phase and beyond) generators produce multiple sinusoidal voltages that are separated by which characteristic?

Introduction / Context:
Polyphase generation creates several sinusoidal voltages simultaneously. The defining feature is their fixed phase displacement, enabling constant power transfer in three-phase systems, smoother torque in machines, and efficient transmission characteristics.

Given Data / Assumptions:

• Polyphase generator (e.g., three-phase) operating under steady-state.
• All phases have the same frequency and (in a balanced system) equal magnitude.

Concept / Approach:
In a polyphase system, the phase voltages are separated by constant phase angles (e.g., 120° in three-phase). Frequency is common to all phases; magnitudes may also be equal in a balanced system, but what uniquely defines polyphase is the constant angular separation, not constant frequency differences or constant currents across phases.

Step-by-Step Reasoning:

Verification / Alternative check:
Three-phase: V_an, V_bn, V_cn share one frequency f and are spaced by 120°. Other polyphase systems (e.g., two-phase historical) use 90° spacing. The spacing is constant by design and does not drift in steady operation.

Why Other Options Are Wrong:

• Certain constant frequencies: All phases share the same frequency, not distinct constant frequencies.
• Certain constant voltages: Magnitudes can be equal in balanced systems, but equality of magnitude is not the defining attribute.
• Certain constant currents: Load-dependent; not intrinsic to generation.

Common Pitfalls:

• Confusing the defining property (fixed phase angles) with other possibly true but non-defining attributes (equal frequency, often equal magnitudes).

Final Answer:
certain constant phase angles