Stepper-motor construction claim: 'Digitally controlled stepping' can be achieved by four stator coils arranged as four pole pairs 45° apart and three ferromagnetic rotor pairs spaced 60° apart. Evaluate whether this specific arrangement statement is sound.

Introduction / Context:
Stepper motors move in discrete angles set by the interaction between stator pole arrangements and rotor teeth or magnets. Common stepper types (variable reluctance, permanent magnet, hybrid) use carefully matched stator/rotor geometries that yield uniform step angles (e.g., 7.5°, 1.8°). The quoted 45° stator spacing with three ferromagnetic rotor pairs 60° apart is inconsistent with standard stepper design practice.

Given Data / Assumptions:

• Four stator coils as four pole pairs 45° apart (implies 8 poles uniform over 360°).
• Three rotor pole pairs 60° apart (implies 6 magnetic poles).
• Goal: digitally controlled discrete stepping.

Concept / Approach:
Uniform stepping requires specific pole/teeth counts so that sequential excitation advances the rotor by a small, repeatable angle. Typical hybrid steppers use many rotor teeth (e.g., 50) and mated stator teeth to obtain 1.8° steps. A coarse geometry with 45° and 60° spacings would lead to large, uneven torque and non-uniform step angles. Moreover, four stator pole pairs and three rotor pairs with those spacings do not form a standard least-common-multiple pattern that yields consistent small steps.

Step-by-Step Solution:
1) Compare to standard designs: hybrid steppers exploit fine tooth counts to achieve small steps.2) Evaluate 45°/60° spacings: these produce 8 and 6 poles respectively, leading to coarse 360/LCM(8,6) = 360/24 = 15° theoretical alignment increments at best, not typical fine steps.3) Practical steppers require precise tooth geometry, not just a few pole pairs at tens of degrees spacing.4) Conclude the described arrangement is not a sound standard for stepper design.

Verification / Alternative check:
Reference textbooks show tooth-count formulas for step angle: step_angle = 360 * (number_of_phases) / (stator_teeth * rotor_teeth) for certain topologies; the claimed geometry does not match common results.

Why Other Options Are Wrong:
“Correct” conflicts with established designs; answers tying it to synchronous AC motors or microstepping change the device type or control method rather than validating the geometry.

Common Pitfalls:
Conflating coarse multi-pole synchronous motors with fine-step steppers; assuming any pole spacing will yield uniform digital steps.

Final Answer:
Incorrect