Design a three-phase induction motor by moving sliders.
Set the output, the voltage and the speed, and the main dimensions, the slots, the winding, the air gap and the performance are worked out live from the textbook equations. The stator and rotor you see are built from your numbers — pull the rotor out and look.
This is an interactive design studio and needs JavaScript to run. Here is what it does.
What it works out
You set the output in kW, the stator voltage, the frequency, the number of poles and the connection. It works out, live: the synchronous speed, the apparent power, the output coefficient, D²L, the bore and the core length, the pole pitch, the net iron length, the flux per pole, the stator turns and conductors per slot, the winding factor with its distribution and pitch parts, the full-load current, the conductor area and the standard wire gauge it rounds to, the slot pitch and slot area, tooth width and tooth density at two conventions, the core depth and the outside diameter, the air gap by two expressions, the rotor bars or the rotor winding, the mean turn lengths, the resistances, the dispersion coefficient and the leakage components, the slip, the torque, the losses and the efficiency.
Every one of those carries the equation it came from, the equation with your numbers substituted, and the page of the textbook — so the flow tab is the whole calculation as a graph you can walk upstream from any answer.
Why the slots are the interesting part
An induction motor is mostly a question about slots. How many the stator has fixes the slot pitch and therefore how finely the winding is distributed; how many the rotor has, relative to the stator, decides whether the machine runs smoothly, hums, vibrates, or sticks at a seventh of its speed and never reaches full load. The second of those is not a refinement — a 24-slot four-pole stator paired carelessly carries an eleventh and a thirteenth harmonic and can crawl at 115 rpm instead of 1500.
The studio treats that as a first-class output rather than a footnote: it names the harmonic, gives the speed the machine would stick at, and says which of the book’s rules your pairing broke.
Method and honest limits
Closed-form classical design after A. K. Sawhney, A Course in Electrical Machine Design, Chapter 10, with the report laid out to IEC 60034. Results are analytical, not finite-element, and nothing here claims otherwise.
Two limits worth knowing. The book gives two routes to the zigzag leakage reactance that disagree by about a quarter, so the engine ships one, publishes both power-factor routes, and warns you when its own two answers conflict instead of quietly picking a winner. And iron loss needs a watts-per-kilogram curve for the actual steel: where one has not been supplied the report says what is missing rather than inventing a figure.
Common questions
How are the main dimensions of an induction motor chosen?
From the output equation. The output coefficient is C₀ = 11·Kw·Bav·ac×10⁻³, and the main dimension product follows as D²L = Q/(C₀·ns), where Q is the apparent power kW/(η·cosφ) and ns the synchronous speed in rev/s. Splitting D²L into a bore and a length needs one more choice — usually the ratio of core length to pole pitch, L/τ — and then D³ = D²L·p/(π·L/τ) (Sawhney Ch. 10).
How big should the air gap of an induction motor be?
Sawhney gives two expressions and the studio publishes both: lg = 0.2 + 2√(D·L) mm (Eqn 10.10) and lg = 0.2 + D mm (Eqn 10.12, D in metres). The gap is the single most expensive millimetre in the machine — widening it raises the magnetising current roughly in proportion, and narrowing it runs into the mechanical reality of bearings, deflection and manufacture.
Which stator and rotor slot combinations should be avoided?
Sawhney’s rules (pp. 618–619) rule out several differences outright: Ss − Sr equal to ±p, ±2p or ±5p gives synchronous cusps, where the motor can lock at a fixed sub-synchronous speed; ±3p gives magnetic locking in a three-phase machine; and ±(p ± 1), ±(p ± 2) and similar give noise and vibration. The studio warns the moment your pairing hits one, and works out the speed it would crawl at from the slot harmonics n = 2Ss/p ± 1.
What is the winding factor, and why does it reduce the voltage?
Kw = Kd·Kp. The distribution factor Kd = sin(qα/2)/(q·sin(α/2)) accounts for the coils of one phase sitting in q different slots, so their emfs add as a fan of phasors rather than arithmetically. The pitch factor Kp = cos(ε/2) accounts for a coil that spans less than a full pole pitch. Both are at most 1, so both reduce the emf per turn — and short-pitching deliberately trades a little of it to kill harmonics.
What is the difference between a squirrel cage and a wound rotor?
A squirrel cage is bars in slots shorted by end rings — nothing to wind, nothing to connect, which is most of why it is the default. A wound (slip-ring) rotor carries a real three-phase winding brought out to three slip rings, so external resistance can be put in the rotor circuit at starting. The studio designs and draws whichever you pick, including the open slot a wound coil needs because it is laid in rather than cast in (Art 10.25).
Built and operated by hjLabs.in.