Design Of Small Electrical Machines Hamdi Review

For the hobbyist or junior engineer, winding a small stator is a nightmare. Hamdi provides a brilliant "fill factor" chart that accounts for real-world manufacturing limitations (not theoretical perfection). He introduces the concept of —accounting for the paper, the varnish, and the air—a detail that separates a working prototype from a short-circuited brick.

Hamdi wrote for the engineer sitting at a drafting table (or CAD station) with a constraint: "It has to fit in a 40mm cube, cost less than $5 in materials, and not catch fire."

Hamdi prescribes a three-pass design method: Design Of Small Electrical Machines Hamdi

: A unique treatment of both permanent magnet (PM) and wound-field D.C. motor designs. Induction Motors

Keywords for further reading: Small motor design, Hamdi design methodology, PMDC motor thermal analysis, fractional horsepower machine optimization, air-gap selection in micro-motors, BLDC design for consumer products. For the hobbyist or junior engineer, winding a

: Given their high power density, small motors are prone to overheating. Hamdi provides detailed strategies for cooling and temperature rise estimation, which are critical for reliability.

Use ferrite magnet (Br = 0.4 T). Air-gap flux density Bg = 0.35 T. Compute flux per pole: ( \phi = B_g \times \pi D L / \text(no. poles) ). For 2 poles, ( \phi \approx 8.25 \times 10^-5 ) Wb. Hamdi wrote for the engineer sitting at a

Where:

Hamdi’s chart gives A = 15,000 A/m for this size (much lower than large machines). Total armature current I_a = T / (B_g × A × D × L × efficiency factor) ≈ 2.1 A.

Applying Hamdi’s method: