Hybrid tool + reportKeyword: 12 pole magnets 9 coil stator
12 Pole Magnets 9 Coil Stator Checker
Run an immediate topology check first, then review evidence, limits, and alternatives in the same URL. This page is scoped for engineers deciding whether a 9-slot/12-pole winding route is ready for prototype, needs validation, or should be redirected.
Published: April 8, 2026•Evidence update: April 8, 2026 (stage1b research-enhance, evidence pass 2)•Review cadence: 6 months or source-change trigger
Tool-first screening
Input your assumptions and run a deterministic result. Every output includes interpretation, uncertainty note, and next-step action.
12-pole / 9-coil stator input panel
Required fields are validated with boundary hints so invalid input can be recovered immediately.
Mechanical speed target for this run.
Helps qualify turns and thermal stress assumptions.
Peak or continuous value should match selected duty mode.
Used for torque-per-amp plausibility boundary.
Integer field. Keep consistent with winding window.
Integer field. Current per path is derived in output.
Compared against duty-specific screening baselines aligned to MG 1 temperature-rise context.
35%-55% is the round-wire reference band; >55% is caution and >65% needs high-fill process proof.
Six-step emphasizes sector-cadence and Hall phasing checks.
Duty type changes thermal screening baseline in this checker; final compliance still needs nameplate-class verification.
Result and action guidance
Output includes direct interpretation plus fallback path when uncertainty is too high.
Empty state: run the checker to generate interpreted output, uncertainty notes, and next-step CTA.
Core conclusions and decision signal
This layer summarizes what can be decided quickly before diving into full report depth.
Topology class
q = 0.25
9-slot + 12-pole + 3-phase sits in fractional-slot concentrated winding territory. It is manufacturable, but tolerance and harmonics need explicit checks.
Commutation cadence
36 sectors / mechanical rev
With 6 pole pairs and six-step control, one mechanical revolution drives 36 commutation sectors. Hall phasing errors scale quickly with speed.
Symmetry boundary
gcd(9,12)=3
A non-trivial symmetry group helps avoid the highest unbalanced-pull class, but does not remove startup ripple or acoustic risk by itself.
Risk trigger
slot fill > 55% (round-wire caution), temp margin < 15°C
NASA guidance places round-conductor slot fill commonly in the 35%-55% band. This page treats >55% as a process-risk warning and >65% as high-risk unless a validated high-fill process exists.
SERP intent confirmation snapshot
Source: web pattern check completed April 8, 2026 for keyword 12 pole magnets 9 coil stator.
| Observed pattern | Evidence summary | Page strategy implication |
|---|---|---|
| How-to winding intent dominates | Top results are winding explainers, calculators, and engineer forum threads around 9-slot/12-pole feasibility. | Tool-first entry must return immediate interpretive output, not a long intro paragraph. |
| Commutation confusion is frequent | Search snippets repeatedly mix six-step sectors, electrical cycles, and mechanical rpm. | The tool must compute electrical frequency and sector cadence directly beside user input. |
| Decision risk lives in boundaries | Many results provide winding diagrams but skip thermal and slot-fill limits. | Report layer should foreground thermal margin, slot-fill cap, and alternatives for high-risk cases. |
Stage1b audit: gap-to-fix conversion
Audit performed before this enhancement pass; only decision-impacting gaps are listed.
| Gap found in current page | Why it was risky | Patch delivered in this pass |
|---|---|---|
| Uncited thermal limits in the checker model | Could be mistaken for compliance limits instead of early-stage screening assumptions. | Mapped thermal discussion to NEMA MG 1 Part 12 temperature-rise clauses and ambient adjustments (S4). |
| Slot-fill warning started too late for round-wire builds | Could delay manufacturability risk detection in manual or random-wound processes. | Introduced two-step boundary: >55% caution, >65% high-risk without qualified high-fill process (S5). |
| Tradeoff table missed electrical-frequency burden at equal rpm | Users could compare topologies without seeing inverter-frequency consequences. | Added reproducible electrical Hz @3000 rpm and six-step sectors/rev dimensions (S2). |
| LCM interpreted as near-proxy for total smoothness | Can lead to wrong choice when torque ripple dominates use-case acceptance. | Added published counterexample and compromise guidance between cogging and ripple (S6). |
Fit and non-fit audience map
Use this before assigning engineering hours or requesting RFQ quotations.
| Audience | Fit status | Reason |
|---|---|---|
| High-speed hobby/RC outrunner refresh | Suitable | The topology is common and lightweight when peak-duty usage is acceptable and winding QC is controlled. |
| Continuous-duty traction or industrial servo | Conditional | Needs stronger thermal path, tighter fill/process control, and often sine-FOC to keep ripple/noise in spec. |
| Low-risk, low-noise medical/precision products | Often not first choice | Alternative slot/pole sets can reduce tuning burden if startup smoothness and acoustic limits are strict. |
| Cost-sensitive retrofit with unknown winding data | Not recommended without teardown data | Unknown turns/fill/thermal class makes tool output uncertain; direct measurement is the minimum executable path. |
Applicability visual
Fast visual split between suitable, conditional, and avoid zones.
If your program sits in the conditional zone, keep this page in screening mode and require verification before committing tooling or procurement.
Method and evidence layer
Tool output is transparent: equations, assumptions, and sources are shown so decisions can be audited.
Computation flow
Input sanitation, formula application, and risk boundary scoring are deterministic.
Reference topology visuals
Coded SVG summaries for formula-heavy parts.
Formula and boundary table
Unknown values are flagged as unavailable rather than filled by guesswork.
| Metric | Expression / rule | Current page value | Boundary rationale |
|---|---|---|---|
| Slots per pole per phase q | q = S / (P * m) | 9 / (12 * 3) = 0.25 | q < 1 indicates concentrated winding class. |
| Electrical frequency | f = rpm * polePairs / 60 | Derived per input | Controller burden and commutation stability scale with electrical frequency. |
| Six-step sector cadence | sectors/s = f * 6 | Derived per input (only six-step mode) | Higher cadence increases timing sensitivity. |
| Thermal screening baseline | duty baseline - declared winding temp = thermal margin | 155°C / 145°C / 170°C baselines by duty mode | Mapped from MG 1 Part 12 temperature-rise context for early screening only; compliance requires full ambient + service-factor declaration. |
| Slot-fill process boundary | >55% caution, >65% high-risk without qualified high-fill process | Derived per input | NASA TM reports 35%-55% as common round-wire slot-fill range; higher fill requires explicit process and AC-loss verification. |
| Periodicity per mechanical rev | LCM(slots, poles) | LCM(9, 12) = 36 | Used for ripple/cogging periodicity discussion. |
| Symmetry group count | gcd(slots, poles) | gcd(9, 12) = 3 | Low gcd combinations need extra caution for unbalanced pull effects. |
| Winding factor exact value | N/A on this page | N/A (geometry-specific) | Requires winding layout details not provided by keyword-level screening inputs. |
Reproducible sample runs (same checker logic)
These rows are computed from the same code path used by the tool. Pick the matching preset and click Calculate result to reproduce each line.
| Preset | Control / duty | rpm | Slot fill | Electrical Hz | Cadence metric | Thermal margin | Risk score | Verdict |
|---|---|---|---|---|---|---|---|---|
| Drone | Six-step / Prototype | 9000 | 58% | 900 | 5400 sectors/s | 30°C | 96 | Prototype-ready |
| E-bike | Sine-FOC / Continuous | 3800 | 63% | 380 | 380 Hz | 10°C | 63 | Validation-required |
| Servo | Sine-FOC / Prototype | 5200 | 52% | 520 | 520 Hz | 40°C | 100 | Prototype-ready |
Mid-page action checkpoint
If your constants are ready, request a boundary review now. If not, return to the tool and rerun with updated inputs.
Research-backed boundary conditions
Added in stage1b to turn formulas into auditable go/no-go criteria with explicit source IDs.
| Boundary statement | Evidence with condition | Decision implication | Source ID |
|---|---|---|---|
| Thermal rise is conditional, not fixed | NEMA MG 1 Part 12.43 lists rise limits at 40°C ambient (e.g., Class F 105°C, Class H 125°C for 1.0 SF) and requires rise derating when ambient >40°C. | Checker outputs are screening-only unless ambient, service factor, and insulation class are explicitly declared. | S4 |
| Lower ambient can legally increase allowable rise | NEMA example: Class F, 1.0 SF, 25°C ambient yields +13°C additional rise (105°C + 13°C = 118°C allowable rise by resistance). | Use ambient-aware arithmetic in RFQ and test plans; avoid copying fixed rise numbers across projects. | S4 |
| Round-wire slot fill has practical range limits | NASA TM reports copper slot fill commonly 35%-55% for round-conductor windings, with 40% as conservative early sizing. | Treat >55% as process caution; require process capability and AC-loss verification before approving >65%. | S5 |
| Hall placement must convert electrical to mechanical angle | TI shows mechanical Hall spacing = 2 / poles × 120 electrical degrees; in 12 poles this is ±20 mechanical degrees. | Commissioning plans must validate pole-count-aware Hall geometry before high-speed or high-current runs. | S3 |
| Commutation ripple vs switching loss is a tradeoff, not a single optimum | Microchip six-step table: Scheme 1 favors lower switching loss but higher current ripple; Scheme 3 lowers ripple at higher switching loss. | Controller strategy should be selected with both inverter thermal budget and torque-ripple target in scope. | S2 |
| Higher LCM/cogging frequency does not guarantee lower torque ripple | KTH results show cases where lower cogging amplitude coexists with higher torque ripple; optimization requires a compromise. | Do not rank slot/pole candidates on LCM alone; include FE/bench ripple checks in final selection. | S6 |
Evidence sources and date context
Core conclusions are tied to explicit sources or marked as uncertain.
| Source ID | Source | Key data used | Context and scope | Date marker |
|---|---|---|---|---|
| S1 | Emetor glossary: Number of slots per pole per phase | Defines q = S / (P * N). States that fractional q < 1 is concentrated winding. | Used for classifying 9-slot/12-pole/3-phase as concentrated winding with q = 0.25. | Copyright footer 2026, accessed April 8, 2026 |
| S2 | Microchip dsPIC33A docs, six-step commutation section and PWM scheme table | Six-step uses 6 sectors per electrical cycle (60 electrical degrees each); Scheme 1 has lower switching loss but higher current ripple, while Scheme 3 lowers ripple with higher switching loss. | Used for sector cadence math plus inverter tradeoff boundaries between commutation ripple and switching loss. | Microchip online docs, accessed April 8, 2026 |
| S3 | TI application brief SLVAEG3 (Hall-sensor commutation) | Mechanical Hall spacing = 2 / pole-count × 120 electrical degrees; for 12 poles this yields ±20 mechanical degrees. | Used to convert electrical-angle rules into buildable mechanical Hall placement for 12-pole commissioning checks. | October 2023 brief, accessed April 8, 2026 |
| S4 | ANSI/NEMA MG 1 Part 12 (watermark PDF) | Part 12.43 lists winding temperature-rise limits at 40°C ambient (for 1.0 SF: Class F 105°C, Class H 125°C) and gives ambient-adjusted rise examples (Class F at 25°C ambient increases to 118°C allowable rise). | Used to clarify thermal boundaries as ambient + insulation-class dependent limits, not single universal numbers. | ANSI/NEMA MG 1-2016 (Rev 2018), watermark ©2021, accessed April 8, 2026 |
| S5 | NASA Technical Memorandum NASA/TM-20230010737 (Glenn Research Center) | Reports copper slot-fill for round conductors typically 35%-55%; recommends 40% as conservative first estimate; notes higher fill with hairpin/bar requires AC-loss accounting. | Used to replace vague slot-fill claims with process-aware boundary bands and explicit high-fill caveats. | September 2023 NASA TM, accessed April 8, 2026 |
| S6 | KTH doctoral thesis: PMSM with non-overlapping concentrated windings (DIVA portal) | Shows counterexamples where lower cogging does not guarantee lower torque ripple, requiring compromise between the two metrics. | Used to avoid overclaiming from LCM-only reasoning and to enforce multi-metric selection in comparison guidance. | Stockholm 2008 thesis, accessed April 8, 2026 |
| S7 | Design and Analysis of a Fractional-Slot Concentrated-Wound PM-Assisted SynRM (DIVA portal) | Defines q = Q / (p * m); discusses slot/pole periodicity and flags low-symmetry combinations as potential unbalanced-force risk areas. | Used for periodicity interpretation and symmetry-risk guardrails in the screening model. | 2015 thesis, accessed April 8, 2026 |
| S8 | NXP AN1961 BLDC control with encoder | In six-step operation, commutation advances every 60 electrical degrees while the torque angle is bounded by inverter state transitions. | Used as secondary boundary support when selecting between quick six-step commissioning and tighter-control alternatives. | July 1, 2005 application note, accessed April 8, 2026 |
Uncertainty register (do not over-interpret)
Items below were checked in this round but still lack reliable open data for universal conclusions.
| Topic | Status | Disclosure note |
|---|---|---|
| Public field-failure rate by slot/pole topology (9/12 vs nearby alternatives) | Pending confirmation | No reliable open-access dataset with comparable duty cycle, thermal class, and controller settings was found in this stage1b pass. |
| Universal hard cap for acceptable slot fill across all winding processes | No single public cap | Available sources provide process-dependent ranges (round-wire vs hairpin/bar), so project-specific process capability data remains mandatory. |
| Exact winding-factor optimum for this page intent | Geometry-dependent | Requires tooth geometry, pitch, and magnet arc details outside keyword-level inputs; this page intentionally leaves it as N/A. |
Alternative comparison and tradeoffs
Compare this topology against adjacent slot/pole options before locking tooling or supplier assumptions.
Slot/pole alternatives table
Reproducible dimensions only: q, periodicity, electrical frequency burden, and decision-impacting tradeoffs.
| Combination | q value | LCM periodicity | Electrical Hz @3000 rpm | Six-step sectors / rev | Benefits | Tradeoff focus |
|---|---|---|---|---|---|---|
| 9-slot / 12-pole (this page) | 0.25 | LCM = 36 | 300 Hz | 36 | Compact concentrated winding, proven in many small BLDC use cases. | Middle electrical-frequency burden; still sensitive to Hall phasing and winding-process variance. |
| 12-slot / 10-pole | 0.40 | LCM = 60 | 250 Hz | 30 | Higher q can ease winding-factor tuning in many three-phase layouts. | Lower electrical frequency helps controller margin, but winding and mechanical envelope usually differ from 9-slot platforms. |
| 12-slot / 14-pole | 0.286 | LCM = 84 | 350 Hz | 42 | Often chosen when low-speed torque bias is preferred over extreme speed. | Electrical frequency is ~16.7% higher than 9/12 at same rpm, increasing inverter and iron-loss pressure. |
Tradeoff profile visual
Visualized decision balance for density, cadence, and manufacturability.
Scenario examples
Each scenario includes assumptions, tool outcome, and minimum next step.
| Scenario | Assumptions | Result interpretation | Minimum next step |
|---|---|---|---|
| 9-slot/12-pole drone retrofit | 9000 rpm, six-step, 32 A phase current, slot fill 58%, winding temp cap 125°C. | Prototype-ready in tool output when Hall phasing is verified and thermal margin remains >20°C. | Run hall-table validation and bench no-load current before full propeller test. |
| E-bike hub upgrade using reused stator | 3800 rpm, sine-FOC, 58 A phase current, slot fill 63%, continuous duty. | Validation-required due to thermal duty and copper loading spread. | Add temperature logging under sustained climb/load cycles before release. |
| Precision servo attempt with unknown winding data | 5200 rpm target, unknown turns and incomplete thermal data. | High-risk due to missing boundary inputs and uncertain torque-per-amp assumptions. | Measure turns, resistance, and no-load back-EMF first, then rerun checker. |
Counterexample guardrail
Source S6: concentrated-winding studies show that lower cogging alone does not guarantee lower total torque ripple.
Use LCM and cogging-frequency arguments as one signal, not as a final selector. Published cases report the need to compromise between cogging reduction and torque-ripple behavior.
Minimum action: keep FE/bench ripple checks in your release gate even when a slot/pole option looks favorable in periodicity math.
Risk and mitigation
At least one mitigation action is attached to every major risk; no risk is listed without an executable follow-up.
Risk map
Impact/probability structure to prioritize test order.
Risk control table
Focus on misuse risk, cost risk, and scenario mismatch risk.
| Risk type | Trigger signal | Mitigation action |
|---|---|---|
| Commutation phasing mismatch | Electrical frequency rises while Hall offset table is unverified. | Validate 6-sector sequence at low speed and lock direction table before full-current tests. |
| Thermal derating ignored | Estimated temp margin < 15°C at duty profile. | Reduce current demand, improve cooling path, or shift to higher-temp magnet/winding class. |
| Slot-fill overreach | Slot fill above 55% with round-wire assumptions, or above 65% without validated high-fill process capability. | Lower turns, enlarge slot window, or qualify hairpin/bar process with explicit AC-loss verification before release. |
| Thermal class mismatch in RFQ handoff | Design assumes Class F/H headline temperatures but ignores ambient and service-factor temperature-rise clauses. | Write RFQ with explicit ambient, service factor, and allowable rise method (resistance/RTD) aligned with MG 1 Part 12. |
| Inverter loss tradeoff ignored | Controller is switched to lowest-ripple six-step PWM without checking switching-loss thermal headroom. | Run a scheme comparison (Scheme 1/2/3) with both current ripple and inverter temperature logging before freeze. |
| Misapplied benchmark transfer | Copying another 9/12 build without confirming stack length and thermal path. | Treat borrowed numbers as hypotheses; re-measure on your own geometry and controller setup. |
FAQ and conversion layer
Decision-focused FAQ followed by clear action routes.
Tool usage and boundary logic
Commutation, control, and frequency
Procurement, reliability, and alternatives
Related engineering routes
Continue from this checker to adjacent implementation pages.
Stage1b gap closure ledger
Review findings converted into implementation-level fixes.
| Gap | Decision risk | Closure delivered |
|---|---|---|
| Thermal boundary wording was too generic for procurement decisions | Teams could misread a single max winding temperature as universal, ignoring ambient/service-factor clauses. | Added NEMA MG 1 Part 12 thermal-rise context and labeled checker thermal limits as screening baselines, not certification limits. |
| Slot-fill threshold lacked process-specific evidence | Using a flat 65% threshold could hide risk for round-wire windings and overstate confidence. | Added NASA TM slot-fill evidence (35%-55% typical round-wire range) and split caution/high-risk triggers. |
| Comparison logic over-relied on LCM/cogging intuition | Users might infer “higher LCM always better,” missing torque-ripple counterexamples. | Added KTH counterexample notes and explicit “cogging vs torque ripple compromise” guidance. |
| Evidence layer did not separate proven facts from open-data gaps | Readers could treat absent public datasets as confirmed negative evidence. | Added an uncertainty register that marks “no reliable public dataset found” items as pending confirmation. |
Next-step CTA
Share your measured constants and duty target; we can return a boundary-aware winding and magnetization recommendation.
Include these fields in your inquiry for fastest response: measured back-EMF at known rpm, turns per tooth, target duty, and thermal ceiling.