750 Watt Hub Motor Number Of Magnets Checker: Tool Result + Deep Decision Report
Run the checker first to get a 750 W pole-count recommendation window and risk status (with wheel-rpm plus gear-ratio handling), then use the report layer to validate method, evidence, market boundaries, and risk controls before design lock, including the 750 watts hub motor 46 magnets decision case.
Published: April 18, 2026 | Evidence updated: April 20, 2026 (stage1b round3: 46-magnet boundary + eCFR/CPSC/UK refresh)
Evidence breadth
26 dated sources
Legal, controller, and supply evidence is tier-tagged to reduce source-mixing errors.
Risk coverage
10 named risks
Each risk has explicit impact and minimum mitigation action.
Decision reproducibility
3 sample runs
Same page model is executed with fixed inputs to expose cadence and thermal boundary changes.
Tool layer: immediate magnet-count screening
Enter your hub-motor assumptions and get deterministic output with recommendation window, uncertainty, and next action.
Quick starts
Start with the 750W baseline, then change one variable at a time so you can attribute risk changes to a specific assumption.
Use wheel rpm here. If geared, set gear ratio below to map wheel speed to motor speed.
Set 1.0 for direct drive. Typical geared hubs can be around 4-7 depending on design and revision.
Typical Br: 1.37-1.42 T. Common SH-grade baseline for traction hubs; keep thermal margin explicit for summer duty.
Canonical route: this tool is designed to directly answer 750 watt hub motor number of magnets on /learn/750-watt-hub-motor-number-of-magnets.
Result layer: interpreted output and next action
Includes empty/loading/error/boundary states and actionable guidance.
Empty state
Start with the 750W baseline and click the checker button. You will get an explicit fit/caution/high-risk verdict with decision notes.
Visual context for recommendation and geometry
Single URL keeps tool and report flow aligned for the same decision.
Report summary: key conclusions and key numbers
750 W first-pass window
32-46 poles (46 poles = 23 pole pairs)
This baseline window is for direct-drive style assumptions. For geared hubs, convert wheel rpm with gear ratio first, then re-evaluate electrical pacing and eRPM stress.
Slot-pole boundary
q = S / (P × m)
Fractional-slot concentrated winding zones can be valid, but low-q combinations increase sensitivity to cogging, ripple, and acoustic variation.
Control pivot
6 sectors per electrical cycle (six-step)
When electrical frequency climbs, six-step commutation ripple becomes harder to ignore and FOC often becomes the practical path.
Market-class boundary
US 750 W != EU EPAC 250 W
A 750 W screen can be valid for U.S. and some state classes, but EU EPAC exclusion text uses <=0.25 kW and 25 km/h cutoff, so legal class must be locked before architecture freeze.
Thermal gate
margin < 15 C = caution
If modeled hotspot approaches grade limits, result confidence drops and the minimum path is thermal test plus lot-level B-H confirmation.
| Audience | Suitable? | Why | Not suitable when |
|---|---|---|---|
| Urban commuter e-bike platform | Suitable with validation | target-pole hubs commonly align with low-to-mid speed requirements when controller and thermal path are matched. | Unknown winding quality or uncontrolled thermal duty. |
| Cargo and delivery continuous duty | Conditional | Works when current and hotspot are controlled with robust cooling and conservative continuous rating. | Natural-air only cooling under high ambient with aggressive current targets. |
| High-speed wheel concepts | Conditional to risky | Feasible only when inverter bandwidth, sensing, and mechanical retention are engineered together. | Six-step strategy with strict NVH/efficiency constraints above high electrical-frequency zones. |
| Retrofit with unknown teardown data | Not suitable yet | Screening can guide what to measure first. | Decision is frozen before confirming pole/slot/grade/thermal facts. |
Stage1b research-enhance audit and closure
Blocker/high items are closed in-page before SEO/GEO handoff.
| Area | Gap found | Impact | Repair | Severity |
|---|---|---|---|---|
| 46-magnet decision execution gap | The page did not give a dedicated 46-magnet speed-chain boundary table, so users had to mentally convert 23 pole pairs and geared ratios. | Teams could pass a direct-drive-safe setup into controller over-speed when moving to geared hubs. | Added a 46-magnet boundary table with wheel rpm / gear ratio / pole pairs / eRPM chain and explicit trigger actions. | high |
| Cross-market legal scope completeness | Cross-market legal boundary was strong for U.S./California/EU but lacked explicit U.S. CPSC testing condition and UK EAPC thresholds. | Decision memos could over-generalize "750 W legal" language across jurisdictions. | Added eCFR/CPSC and GOV.UK EAPC evidence rows with explicit watt/speed thresholds and consequences when outside scope. | high |
| Jurisdiction boundary | The page used 750 W as a technical class but did not clearly separate U.S./state classes from EU EPAC legal limits. | Teams could ship a technically valid setup into the wrong legal category. | Added U.S. federal, California, and EU legal-threshold evidence with explicit numeric limits and date context. | high |
| Geared-hub rpm interpretation | Wheel rpm was treated as motor rpm everywhere, with no explicit gear-ratio conversion boundary. | Electrical frequency and controller stress could be under-estimated by multiples on geared hubs. | Added gear-ratio input, effective pole-pair math, and eRPM boundary examples from controller manuals. | high |
| Evidence stratification | Primary regulations and vendor manuals were presented in one flat source list. | Readers could not quickly distinguish normative constraints from implementation examples. | Annotated core decisions with regulation-first references, while keeping vendor manuals explicitly scoped as architecture examples. | high |
| Comparison with counterexamples | Comparison lacked direct-drive vs geared numeric counterexamples and controller-limit triggers. | Users could miss the point where a "good" pole count becomes non-viable under real controller limits. | Added decision matrix rows for effective pole pairs, eRPM threshold examples, and legal-class mismatch triggers. | medium |
| Unknown-data disclosure | Dataset limitations were stated, but source volatility and model-year drift risks were not explicit. | A fixed pole-count assumption could survive too long even after supplier-side spec changes. | Added vendor-spec volatility note and an execution path: lock versioned docs + BOM revision trace before release. | medium |
Deep layer: method and evidence
Method flow (encoded SVG)
The checker logic is explicit so assumptions and trust limits are auditable.
Method details
1. Normalize assumptions
Lock the 750 W screening basis first, then enter even magnet count, slot count, phase count, wheel rpm, gear ratio, and ambient/cooling context.
2. Compute electromagnetic pacing
Derive pole pairs, q-value, electrical frequency, and commutation cadence for the selected control mode.
3. Estimate thermal and load indicators
Estimate torque constant, continuous torque potential, radial-load index, and hotspot margin versus chosen grade.
4. Map to action bands
Convert indicators into fit/caution/high-risk bands with explicit uncertainty and minimum next action.
5. Screen concentration and compliance exposure
Check sourcing concentration and policy thresholds before locking BOM assumptions for production programs.
Reproducible sample runs (model output)
First-hand evidence from this page model: fixed inputs produce explicit cadence, risk, and next-action outputs.
| Case | Input snapshot | Output snapshot | Verdict | Minimum next action |
|---|---|---|---|---|
| 46 magnets direct-drive commuter | 46 poles / 42 slots / 520 wheel rpm / ratio 1.00 | 199.3 Hz · 30/100 | fit | Proceed to FEA + thermal test planning using this configuration as baseline, then lock supplier-grade data pack. |
| 46 magnets geared commuter (5:1) | 46 poles / 42 slots / 520 wheel rpm / ratio 5.00 | 996.7 Hz · 86/100 | high-risk | Take the minimum executable path: normalize power basis, reduce stress drivers (rpm/current), and rerun before committing tooling or BOM. |
| 46 magnets cargo climb (4:1) | 46 poles / 42 slots / 380 wheel rpm / ratio 4.00 | 582.7 Hz · 86/100 | high-risk | Take the minimum executable path: normalize power basis, reduce stress drivers (rpm/current), and rerun before committing tooling or BOM. |
Jurisdiction boundary matrix
Lock legal class before architecture freeze. 750 W is not a globally interchangeable legal category.
| Market scope | Numeric threshold | Why it matters | Minimum action | Source |
|---|---|---|---|---|
| U.S. federal low-speed e-bike scope | Motor less than 750 W and less than 20 mph on motor power alone (with operable pedals). | Supports using 750 W as a screening class in U.S.-focused commuter programs. | Use as initial legal-scope anchor, then verify state-level class constraints. | R0 |
| U.S. CPSC low-speed definition test condition (16 CFR 1512.2) | Low-speed e-bike definition uses fully operable pedals, motor less than 750 W, and less than 20 mph on paved level surface with a 170 lb operator. | Adds the federal test-condition detail frequently missed in product and compliance handoffs. | Keep benchmark inputs aligned to this condition before asserting federal low-speed equivalence. | R23 |
| California classes (updated law text) | Class 1/2/3 retain <=750 W, with Class 3 pedal-assist cutoff at 28 mph and amended text effective January 1, 2025. | Shows that speed class and labeling obligations matter even when wattage is unchanged. | Freeze class target in requirements before motor/control calibration. | R16 |
| EU EPAC exclusion boundary (Regulation 168/2013) | Pedal assistance exclusion text uses maximum continuous rated power <=0.25 kW and assistance progressively cut at 25 km/h. | A U.S.-style 750 W assumption does not directly map to EPAC legal scope. | If EU launch is in scope, run a separate compliance path before committing architecture. | R17 |
| Great Britain EAPC practical legal threshold | EAPC guidance uses max continuous rated power <=250 W and assistance cut-off at 15.5 mph; non-qualifying vehicles are treated as motor vehicles. | Prevents carrying 750 W assumptions into UK launch planning without a class remap. | If UK market is in scope, branch to EAPC/LPM assessment before commercialization. | R24 |
Geared-hub eRPM check cases
Controller-manual examples are not universal limits, but they are actionable for stage-1 falsification.
| Case | Input signal | Implication | Action | Source |
|---|---|---|---|---|
| Direct-drive baseline math | 40 magnets => 20 pole pairs; controller-limited example at 28,000 eRPM. | Mechanical rpm limit is about 1,400 rpm (28,000 / 20) in that controller family. | Use as a quick pace check only; final limit depends on your specific controller and sensing mode. | R18 |
| Geared-hub conversion example | 32 magnets => 16 pole pairs and 7:1 reduction ratio on the drivetrain side. | Equivalent wheel rpm can collapse to about 250 rpm when the same 28,000 eRPM cap is applied. | Always convert wheel rpm to motor mechanical rpm before interpreting checker cadence. | R18 |
| Controller effective pole pairs | Phaserunner guidance treats geared hubs with effective pole pairs = magnetic pole pairs x gear ratio. | Effective control settings can be much higher than physical rotor pole pairs. | Track physical and controller-effective pole values separately in commissioning sheets. | R19 |
46 magnets (23 pole-pair) boundary table
This table converts the full speed chain so the keyword case is executable instead of slogan-level.
| Case | Wheel rpm | Gear ratio | Pole pairs | Estimated eRPM | Decision implication | Source |
|---|---|---|---|---|---|---|
| 46 magnets direct-drive commuter baseline | 520 rpm | 1.0 | 23 | ~11,960 eRPM | Usually below common controller benchmark examples, but still requires control-mode and thermal checks. | R2, R18 |
| 46 magnets geared commuter with 5:1 reduction | 520 rpm | 5.0 | 23 (effective becomes much higher in controller settings) | ~59,800 eRPM | Can exceed controller-family examples quickly; wheel-rpm-only checks will understate risk. | R18, R19, R25 |
| 46 magnets cargo climb with 4:1 reduction | 380 rpm | 4.0 | 23 | ~34,960 eRPM | May still breach conservative sensorless eRPM examples depending on controller architecture. | R18, R25 |
Applicability boundaries
Use these rows to decide when checker output is reliable and when escalation is mandatory.
| Boundary | Valid when | Fails when | Minimum action | Source |
|---|---|---|---|---|
| Magnet count parity | Even magnet count; checker range 20-80. | Odd count or outside range. | Correct pole count first, then rerun. | R2 |
| Slot-pole-phase q window | q roughly 0.2-0.55 for this stage-1 screen. | q below 0.2 or above 0.55 without special design intent. | Re-evaluate slot/pole pairing and winding strategy. | R1, R11 |
| Commutation pacing | Electrical frequency and cadence remain within controller bandwidth. | High electrical frequency with six-step mode under strict NVH targets. | Switch to FOC or lower target rpm before geometry freeze. | R2, R3 |
| Wheel-rpm vs motor-rpm mapping | Direct-drive uses gear ratio = 1.0, or geared hubs apply measured reduction ratio before electrical-frequency checks. | Geared hubs are screened with wheel rpm as if it were rotor rpm. | Use motor mechanical rpm = wheel rpm x gear ratio, then recalculate electrical frequency and effective pole pairs. | R18, R19 |
| Hall sensor geometry mapping | Mechanical Hall placement is converted from electrical angle using actual pole count. | Electrical-angle assumptions are reused without recalculating mechanical placement. | Recalculate commissioning geometry before releasing Hall sensor fixture and calibration plan. | R3 |
| Thermal confidence | Estimated thermal margin >= 15 C. | Margin below 15 C or hotspot estimate uncertain. | Run thermal test + lot-level magnetic curve confirmation. | R4, R5 |
| Power-basis consistency | Inputs and targets are locked to one declared continuous/rated basis. | Peak-only marketing values are mixed into continuous screening. | Convert all benchmark points to a continuous basis (or explicitly stay in peak basis) before comparison. | R6, R7 |
| Market legal-class fit | Target market is declared and motor/speed limits are mapped to that market class before release. | A single 750 W assumption is reused across markets without legal-class remap. | Lock jurisdiction scope (U.S./state/EU etc.) and run class-specific compliance review before SOP freeze. | R0, R16, R17, R24 |
| Federal low-speed test-condition alignment | Motor-only speed and rider/test assumptions are aligned with the declared legal definition basis. | Marketing speed or rider assumptions are mixed into legal-class claims without condition mapping. | Record rider/test condition with each legal claim in requirement docs and compliance checklists. | R22, R23 |
| Supply concentration and compliance exposure | Single-country dependence and sourcing plan are explicitly checked against policy and business limits. | Program assumes stable supply with no diversification path despite concentrated value-chain signals. | Run sourcing stress test and define dual-source or fallback-grade path before SOP freeze. | R8, R9, R10 |
Evidence table with explicit date context
Time markers are included to reduce stale interpretation risk.
| ID | Source | Key data | Decision use | Date / scope |
|---|---|---|---|---|
| R0 | U.S. Code (govinfo) 15 U.S.C. 2085 low-speed electric bicycle definition | Defines low-speed electric bicycle scope with operable pedals, less than 20 mph on motor power alone, and motor output of less than 750 watts. | Anchors the U.S.-centric 750 W screening class so this page does not over-claim global legal applicability. | U.S. Code 2023 package (published Feb 2026), accessed April 18, 2026 |
| R1 | Emetor glossary: slots per pole per phase | Defines q = S / (P × m) and clarifies fractional-slot concentrated winding context. | Used for q-value definition in this checker; treated as a secondary explainer, not a formal standard. | Accessed April 18, 2026 |
| R2 | Microchip BLDC six-step documentation | Six-step uses 6 sectors per electrical cycle, 60 electrical degrees each, and Np electrical cycles per one mechanical revolution. | Used for cadence model and control-mode guidance at high electrical frequency. | Accessed April 18, 2026 |
| R3 | TI SLVAEG3 hall commutation brief | For a 12-pole example, 120 electrical degree Hall separation maps to about +/-20 mechanical degrees. | Used to explain why pole count and controller phasing cannot be separated in commissioning. | Published 2023, accessed April 18, 2026 |
| R4 | NASA/TM-20230010737 electric machine winding guidance | Round-conductor slot fill is commonly around 35%-55% for first-pass assumptions; 40% is suggested as conservative initial estimate. | Used for manufacturability and thermal-risk boundary when slot fill assumptions are optimistic. | September 2023, accessed April 18, 2026 |
| R5 | Arnold magnetic materials catalog (vendor data) | Public grade tables list NdFeB/SmCo remanence and temperature-class tradeoffs; values are catalog-level and not a universal standard. | Used as indicative grade-screening reference only; final limits still need supplier lot data. | Catalog accessed April 18, 2026 |
| R6 | UN Regulation No. 85 (UNECE official text) | Defines maximum 30 minutes power as the average over 30 minutes; requires defined conditioning and controlled power band for test. | Used to lock power-basis interpretation and avoid peak-vs-continuous mixing in design screening. | Revision 1 text (2013), accessed April 18, 2026 |
| R7 | EMRAX 228 datasheet v1.6 | Publishes peak (S2, 2 min) and continuous (S1) ratings side by side in one product sheet. | Used as practical evidence for keeping peak and continuous basis separate in checker input. | Version 1.6 March 2025, accessed April 18, 2026 |
| R8 | USGS Mineral Commodity Summaries 2026: Rare Earths | U.S. net import reliance is listed as 67% in 2025; China share of U.S. imports is listed as 71% (2021-2024). | Used for sourcing-risk and concentration-risk framing in procurement decisions. | February 2026 |
| R9 | IEA Rare Earth Elements executive summary | For 2024, China share is stated as 60% in mining, 91% in refining, and 94% in permanent-magnet production. | Used for concentration-risk and diversification urgency in long-term platform planning. | 2026 report, accessed April 18, 2026 |
| R10 | European Commission Critical Raw Materials Act page | States 2030 benchmarks: extraction >=10%, processing >=40%, recycling >=25%, and <=65% from one third country. | Used to set compliance-aware sourcing boundaries for EU-facing programs. | CRMA adopted in 2024, accessed April 18, 2026 |
| R11 | LUT academic work on fractional-slot PM synchronous machines | Documents that q < 1 concentrated winding configurations can increase harmonic, cogging, and torque-ripple sensitivity. | Used to justify treating low-q combinations as validation-heavy instead of auto-accepting by rule of thumb. | Academic publication, accessed April 18, 2026 |
| R12 | BAFANG workbook 2024 (official PDF) | Lists hub-motor models that include 750 W class configurations, illustrating that "750 W" is a power class while magnetic/electromagnetic implementation differs by model. | Used to justify that magnet-count decisions cannot be inferred from wattage alone. | Workbook 2024 PDF, accessed April 18, 2026 |
| R13 | Grin Baserunner manual (motor settings table) | Documents that geared hubs can use effective pole-pair settings that differ from physical rotor pole count in controller configuration. | Used for the "effective pole pairs vs physical poles" boundary and to prevent controller-setting confusion. | Rev 1.0 PDF, accessed April 18, 2026 |
| R14 | Grin G62 hub motor product page | Lists a geared motor type with power range 600-1200 W and controller-facing magnetic pole-pair settings (50). | Used as a vendor-level geared architecture example where controller settings can be much higher than physical rotor pairs. | Accessed April 18, 2026 |
| R15 | QS Motor product page (hub motor pole-pair diversity) | Publishes hub-motor variants with explicit pole-pair specifications, reinforcing that pole count is architecture-specific and not a direct function of rated wattage. | Used as comparison evidence for "do not infer exact magnet count from wattage alone." | Accessed April 18, 2026 |
| R16 | California Vehicle Code section 312.5 | Defines Class 1/2/3 e-bikes with <=750 W and class-specific speed boundaries including 28 mph pedal-assist for Class 3, with amended text effective January 1, 2025. | Used to show that wattage alone is not enough; legal class and speed cutoff must be part of architecture decisions for California programs. | Updated by SB 1271 (2024), effective Jan 1, 2025; accessed April 18, 2026 |
| R17 | Regulation (EU) No 168/2013 consolidated text (Article 2(2)(h)) | Article 2(2)(h) excludes pedal-assist cycles only when maximum continuous rated power <=0.25 kW and assistance is progressively cut and finally cut before 25 km/h. | Used to mark explicit non-equivalence between U.S.-style 750 W assumptions and EU EPAC legal framing. | Consolidated text dated Feb 20, 2019; accessed April 18, 2026 |
| R18 | Grinfineon controller manual v2.1 | Documents controller-side eRPM guidance, including a 28,000 eRPM sensorless benchmark and conversion examples for direct-drive and geared hubs. | Used to add executable geared-hub conversion boundaries and to prevent wheel-rpm interpretation errors. | Rev 2.1 PDF, accessed April 18, 2026 |
| R19 | Phaserunner manual rev2.0 | States that geared hubs require effective pole pairs = magnetic pole pairs x gear reduction ratio and provides common DD/geared examples. | Used to formalize the checker boundary between physical poles and controller-effective pole settings. | Rev 2.0 PDF, accessed April 18, 2026 |
| R20 | BAFANG workbook 2024 (official PDF) | Shows mixed rated-power variants (including 750 W and 1000 W) within related motor families and includes a note that specifications are for reference and subject to change. | Used to prevent hard-coding a magnet-count rule from a single catalog snapshot and to require model-year/version traceability. | Workbook 2024 PDF, accessed April 18, 2026 |
| R21 | Grin DD45 direct-drive product page | Lists direct-drive motor type with lower controller-facing pole-pair settings (23) than geared examples on the same vendor platform. | Used as a counterexample pair with geared listings to show architecture-driven pole-setting divergence. | Accessed April 18, 2026 |
| R22 | U.S. CPSC summary report: Electric and Non-Powered Bicycle Standards | States 16 CFR Part 1512 requirements apply to low-speed e-bikes and summarizes low-speed definition alignment with <750 W and <20 mph motor-only scope. | Used to separate federal consumer product safety scope from state class rules in decision documentation. | October 2024 report, accessed April 20, 2026 |
| R23 | eCFR 16 CFR 1512.2 definition text | Defines low-speed e-bike with fully operable pedals, motor less than 750 W, and less than 20 mph on paved level surface with a 170 lb operator. | Used to pin legal test condition details and reduce ambiguous "750 W compliant" statements. | Current eCFR page, accessed April 20, 2026 |
| R24 | GOV.UK EAPC standards and legal requirements | States EAPC threshold at <=250 W continuous rated power with assist cut-off at 15.5 mph and classifies non-qualifying vehicles as motor vehicles. | Used to prevent UK market misuse of U.S.-centric 750 W assumptions in commercialization decisions. | Public update marker Dec 10, 2024; accessed April 20, 2026 |
| R25 | ODrive API reference (electrical vs mechanical revolutions) | Documents that electrical-revolution quantities are tied to pole pairs and must be converted to motor turns by dividing by pole pairs for certain calibration fields. | Used as an independent technical cross-check that physical/mechanical and electrical bases must be tracked separately. | Docs v0.6.11 page, accessed April 20, 2026 |
Evidence confidence tiers
Use tier ordering to avoid mixing regulatory constraints with implementation examples.
| Tier | Scope | IDs | How to use in decisions |
|---|---|---|---|
| Tier A: normative/legal constraints | Binding legal definitions, vehicle class boundaries, and regulatory test conditions. | R0, R6, R16, R17, R22, R23, R24 | Use first for go/no-go legal framing; do not override with vendor examples. |
| Tier B: primary technical control references | Controller/commutation/electrical-basis references used for executable engineering checks. | R2, R3, R18, R19, R25 | Use for cadence math, effective pole-pair settings, and commissioning boundaries. |
| Tier C: market and product examples | Vendor catalogs/product docs showing architecture diversity and spec drift risk. | R12, R13, R14, R15, R20, R21 | Use as counterexamples and feasibility context, not as universal rules. |
| Tier D: evidence gaps | High-impact areas without reliable public cross-vendor datasets. | Known-unknown table | Mark as pending and require internal validation data before release decisions. |
Stage1b evidence increments (new facts only)
These rows list only decision-relevant additions from this research refresh, not paraphrases of existing copy.
| Topic | New fact with explicit time | Decision impact | Source |
|---|---|---|---|
| 750 W class anchor | U.S. federal low-speed e-bike text explicitly includes the less-than-750-watt limit with less-than-20-mph motor-only scope. | Keeps this page scoped to one legal context instead of mixing commuter and high-power classes blindly. | R0 |
| State-level class constraints | California section 312.5 keeps <=750 W but separates Class 1/2/3 by assist/throttle behavior and speed thresholds, with amended text effective January 1, 2025. | A "750 W only" decision can still fail class-fit requirements if speed/control behavior is mismatched. | R16 |
| EU legal boundary | EU 168/2013 Article 2(2)(h) uses <=0.25 kW continuous and 25 km/h assist cutoff for EPAC exclusion. | Prevents direct reuse of U.S.-style 750 W assumptions in EU-bound product planning. | R17 |
| Federal low-speed test condition details | eCFR 16 CFR 1512.2 includes a 170 lb operator condition alongside <750 W and <20 mph motor-only criteria in the low-speed definition. | Prevents legal-class claims from being detached from test-condition assumptions. | R23 |
| CPSC applicability framing | CPSC 2024 summary states 16 CFR Part 1512 applies to low-speed e-bikes as well as non-powered bicycles in consumer-safety context. | Keeps product-safety obligations visible instead of treating wattage labels as sufficient compliance evidence. | R22 |
| Great Britain EAPC boundary | GOV.UK EAPC guidance uses <=250 W continuous rated power and 15.5 mph assist cut-off; outside this boundary, vehicle handling shifts to motor-vehicle rules. | Adds a practical cross-market counterexample against reusing U.S.-centric 750 W assumptions. | R24 |
| Six-step commutation cadence | Six-step uses 6 sectors at 60 electrical degrees each, and electrical cycles scale with pole-pair count. | A target-pole motor (23 pole pairs) reaches high electrical cadence quickly, so controller strategy becomes an early architecture constraint. | R2 |
| Hall geometry conversion | TI shows that in a 12-pole case, 120 electrical degrees maps to about +/-20 mechanical degrees. | Pole-count changes require re-commissioning Hall geometry; reusing old fixtures increases startup and commutation risk. | R3 |
| Continuous rating basis | UN R85 defines maximum 30-minute power as a 30-minute average under specified conditions. | Prevents peak-only claims from being treated as continuous capability in thermal sizing and supplier selection. | R6, R7 |
| Geared-hub eRPM conversion | Controller guidance gives worked examples where 28,000 eRPM maps to very different wheel rpm once pole pairs and gear ratio are applied (for example 32 magnets with 7:1 gearing -> about 250 wheel rpm). | Wheel-rpm input must be converted before cadence judgment, or risk is systematically under-estimated. | R18 |
| Effective pole-pair boundary | Phaserunner guidance states geared effective pole pairs are calculated from magnetic pole pairs multiplied by reduction ratio. | Explains why controller settings can differ from physical rotor pole counts without implying a data error. | R19 |
| Electrical vs mechanical basis conversion | ODrive API reference documents electrical-revolution values that must be converted through pole-pair relationships to get motor-turn values. | Adds an independent technical source supporting the same physical-vs-effective separation used in geared-hub checks. | R25 |
| Architecture counterexample pair | The same vendor context can show geared examples around 50 controller-facing pole pairs while direct-drive examples can sit near 23. | Demonstrates that rated power alone does not identify a unique pole-count target. | R14, R21 |
| Slot-fill realism | NASA TM cites 35%-55% round-conductor slot fill with 40% as a conservative first estimate. | Overstating slot fill inflates torque expectation and can hide hotspot risk during early screening. | R4 |
| Rare-earth supply concentration | USGS reports 67% U.S. net import reliance (2025), while IEA reports 2024 concentration at 60% mining, 91% refining, and 94% magnets in China. | Single-source assumptions create cost and availability risk for long-life programs. | R8, R9 |
| Policy boundary for diversification | EU CRMA 2030 benchmarks include <=65% dependence on one third country plus extraction/processing/recycling targets. | Programs serving EU markets need sourcing plans aligned to policy-driven diversification expectations. | R10 |
| Catalog volatility disclosure | Official BAFANG workbook notes specifications are for reference and subject to change across versions. | Enforces model-year and document-version checks before using catalog numbers as hard design constraints. | R20 |
Comparison and alternatives
Decision dimensions with counterexamples and limits
Each row includes a falsification path so 750W assumptions are not treated as universal truths.
| Dimension | 750W baseline signal | Counterexample / limitation | Minimum action | Source |
|---|---|---|---|---|
| Electrical pacing at top speed | 40 poles => 20 pole pairs; at 520 rpm this is about 173 Hz electrical in a typical 750 W baseline. | Higher-pole options (for example 46 poles) can raise electrical frequency quickly at the same wheel speed. | Decide topology with controller bandwidth and NVH targets in the same design review. | R2 |
| Geared-hub cadence conversion | Controller manuals show eRPM checks must include both pole pairs and gear ratio, not wheel rpm alone. | A wheel-rpm-only check can hide controller stress by multiples when reduction ratio is high. | Compute motor mechanical rpm = wheel rpm x gear ratio before finalizing pole-count decisions. | R18, R19 |
| 46-magnet (23 pole-pair) speed-chain stress test | At 520 wheel rpm with direct drive, 46 magnets implies about 11,960 eRPM (23 x 520). | At the same wheel rpm with 5:1 gearing, motor-side pacing jumps to about 59,800 eRPM. | Always run the full chain (wheel rpm x ratio x pole pairs) before accepting a 46-magnet target. | R2, R18, R25 |
| Commutation commissioning | Hall placement must be converted from electrical to mechanical angle using actual pole count. | A Hall fixture that works on one pole count can miscommutate after pole-count changes. | Recompute Hall geometry and re-run startup/ripple validation after any pole-count change. | R3 |
| Legal class alignment by market | U.S./California definitions preserve <=750 W classes, while EU/UK practical boundaries use <=0.25 kW or <=250 W with 25 km/h or 15.5 mph assist cutoffs. | A design that is compliant in one region can fall into the wrong legal vehicle class in another. | Lock market-jurisdiction target before freezing control limits, top speed, and product labeling. | R0, R16, R17, R24 |
| Continuous torque and power claims | R85 and product datasheets distinguish continuous (S1/rated) from short-duration peak (S2). | Using peak numbers as continuous inputs can make a high-risk architecture look acceptable. | Lock one rating basis in requirements and reject mixed-basis supplier comparisons. | R6, R7 |
| Winding-risk sensitivity (q and harmonics) | q-value is useful for screening, and low-q concentrated winding can raise ripple sensitivity. | q alone does not predict final torque ripple without geometry-specific simulation and tests. | Treat low-q outcomes as validation-heavy, not as automatic fail/pass. | R1, R11 |
| Sourcing resilience and policy fit | USGS/IEA signal concentrated rare-earth supply; EU CRMA adds diversification benchmarks. | A cost-optimal single-source BOM may fail resilience or compliance expectations in later gates. | Add dual-source/fallback-grade plan before SOP and before long-term price negotiation. | R8, R9, R10 |
| Physical poles vs controller-effective poles | Vendor docs can show geared examples with controller-facing pole-pair settings far above direct-drive examples. | Copying one controller pole-pair number as rotor magnet count can produce wrong BOM or wrong replacement orders. | Record both physical poles and controller-effective poles in validation sheets before procurement. | R14, R19, R21 |
| Catalog-version stability | Official vendor catalogs can include explicit notes that specifications are references and subject to change. | A historical catalog value can become stale before production lock and silently invalidate assumptions. | Version-pin supplier docs and tie every key motor parameter to a dated revision record. | R20 |
Architecture comparison table
Compare options on one declared basis before making a sourcing or tooling decision.
| Option | Strengths | Tradeoffs | Use when |
|---|---|---|---|
| 40-pole direct-drive baseline (750 W commuter screen) | Balanced low-speed torque potential, straightforward wheel-rpm interpretation, and stable first-pass controller tuning. | Electrical frequency still rises at speed, and retention/thermal path must be validated for sustained duty. | Urban direct-drive e-bike or scooter programs with validated thermal assumptions and FOC-ready control. |
| Geared hub with high effective pole pairs | Can improve launch feel and packaging flexibility while keeping wheel torque competitive. | Effective pole-pair count can become much higher than physical poles, increasing eRPM/controller-limit sensitivity. | Low-to-mid speed duty where reduction ratio and controller limits are modeled together from day one. |
| High-pole direct-drive architecture | Higher magnetic event density can improve low-speed smoothness and startup behavior. | Higher electrical pacing pressure with stronger dependence on commutation strategy and NVH tolerance. | Heavy-load low-speed duty with robust controller bandwidth and measured thermal margin. |
| Mid-drive IPM/PMSM alternative | Can reduce unsprung mass and move thermal load away from wheel hub. | Introduces drivetrain complexity, gearbox losses, and packaging differences. | When suspension dynamics or high-continuous power density dominates architecture choice. |
Live thermal-frequency risk matrix (encoded SVG)
Marker uses current result values when available.
Result snapshot cards
Torque constant estimate
0.173 Nm/A
Directional estimate for screening only; not a release-level guarantee.
Thermal margin
70.6 C
Below 15 C enters caution gate in this workflow.
Radial-load index
0.822
High or low extremes increase retention and ripple risk.
Risk controls and boundaries
Risk register
Magnet delamination under repeated thermal cycling
Impact: Air-gap damage, torque ripple growth, and potential catastrophic rotor contact in severe cases.
Mitigation: Validate adhesive system at duty-cycle temperature profile and run mechanical overspeed margin tests.
Geared-hub eRPM miscalculation
Impact: Controller commissioning and cadence risk are underestimated when wheel rpm is used without ratio conversion.
Mitigation: Record gear ratio explicitly, convert wheel rpm to motor rpm, and validate controller eRPM margin before release.
Controller mismatch at high electrical frequency
Impact: Commutation loss, acoustic noise, and lower efficiency near top-speed band.
Mitigation: Run controller-inverter co-validation with electrical-frequency target from checker output.
Over-optimistic slot fill assumptions
Impact: Copper loss and hotspot rise exceed expectation, invalidating nominal torque plan.
Mitigation: Use process-realistic fill assumptions and verify with winding-process capability data.
Cross-market legal-class mismatch
Impact: A configuration approved in one market can require different class handling or approval path in another market.
Mitigation: Freeze target jurisdiction early and map motor/speed/control settings to that jurisdiction before tooling lock.
Low-speed definition condition mismatch
Impact: A project can appear compliant by watt label but fail legal definition context when rider/test assumptions are inconsistent.
Mitigation: Document definition basis (including operator/test assumptions) in compliance gates and supplier claims.
Peak-vs-continuous basis confusion
Impact: Design appears feasible on paper but fails continuous thermal validation.
Mitigation: Freeze one declared power basis before architecture comparison and supplier shortlisting.
Catalog drift and stale assumptions
Impact: Model-year or revision changes can invalidate magnet-count and rating assumptions used in earlier decisions.
Mitigation: Tie critical parameters to dated supplier revisions and re-check before RFQ closure.
Rare-earth supply concentration shock
Impact: Lead-time and price volatility can invalidate launch timing and margin assumptions.
Mitigation: Use dual-source/fallback-grade planning and contract clauses linked to concentration-risk events.
Policy-misaligned sourcing for EU-facing programs
Impact: Late-stage compliance and customer acceptance risk if diversification expectations are ignored.
Mitigation: Run a CRMA-aware sourcing check before RFQ closure and before long-term nomination.
Known unknowns (explicitly not overclaimed)
These are intentionally marked uncertain to avoid false confidence.
| Topic | Status | Decision impact | Minimum executable path |
|---|---|---|---|
| Open dataset of 46-magnet adoption by model year | No reliable public cross-vendor dataset quantifies 46-magnet prevalence by model year and controller firmware. | High impact on retrofit and procurement assumptions. | Build an internal model-year trace table linking physical poles, firmware settings, and validated teardown records. |
| Global mapping of hub-motor power class vs magnet count | No reliable public dataset yet (暂无可靠公开数据). | High impact on benchmarking and teardown-based assumptions. | Build an internal benchmark dataset from verified teardown and dyno-linked records before setting hard rules. |
| Public crosswalk of physical poles vs controller-effective pairs | No reliable open dataset spans model-year changes across major hub vendors. | High impact on retrofit and replacement accuracy. | Maintain an internal traceable map (model, firmware, physical poles, effective pairs, ratio). |
| Lot-level irreversible demag curves at actual hotspot | Public catalog values are not enough for final confidence. | High impact on overload and abuse-case durability. | Request supplier lot data + run elevated-temperature demag verification. |
| Rotor retention margin at overspeed | Depends on adhesive, sleeve, and manufacturing process details. | High safety and reliability impact. | Mechanical FEA + burst/overspeed test before SOP freeze. |
| Real road thermal boundary for enclosed hubs | Vehicle airflow and riding profile create high variance. | Medium-high impact on continuous torque promise. | Instrumented road cycle + thermal calibration loop. |
| Long-term supply volatility exposure | Depends on contract terms and regional sourcing footprint. | Medium impact on cost and lead-time resilience. | Dual-source plan with grade fallback and inventory trigger policy. |
Scenario examples
Scenario A: 750 W commuter baseline (48 V, 520 rpm)
Assumptions: 3-phase, 36 slots, FOC control, natural-air cooling, moderate ambient conditions.
Expected outcome: Usually lands in fit/caution boundary depending on electrical cadence and thermal margin.
Scenario B: Cargo duty continuous climb
Assumptions: Higher current, lower rpm, elevated ambient, long duty period.
Expected outcome: Thermal margin often becomes the dominant risk trigger even when q-value looks acceptable.
Scenario C: High-speed performance wheel
Assumptions: Near 1000 rpm wheel speed and high bus voltage target.
Expected outcome: Electrical frequency and controller pacing become first-order constraints.
Scenario D: Unknown teardown data retrofit
Assumptions: Missing confirmed slot count, grade, and hotspot behavior.
Expected outcome: Output should be treated as directional only; minimum path is teardown + measurement.
Scenario E: Geared hub with ratio-sensitive cadence
Assumptions: Wheel rpm appears moderate, but internal reduction ratio is above 4:1 and controller eRPM headroom is limited.
Expected outcome: Risk can jump from fit to caution/high-risk once motor-side cadence is converted correctly.
Related internal routes
Continue decision depth
Keep one canonical 750 W magnet-count URL while linking to adjacent decision topics.
Hub motor hybrid checker
Use for broader hub-motor decisions beyond the 750 W envelope.
12 pole magnets 9 coil stator checker
Use when slot-pole commutation questions dominate design iteration.
Interior permanent magnet motor checker
Use for mid-drive/IPM alternatives and higher-speed architecture tradeoffs.
Axial flux motor magnets hybrid page
Use when topology migration beyond radial hub architecture is under review.
89mm arc magnets neodymium checker
Use when moving from hub pole-count checks to OD-around-89 mm arc-segment sourcing and retention screening.
750 watts hub motor 46 magnets checker
Use when you want the dedicated 46-magnet route with geared-boundary defaults.
Engineering RFQ intake
Use for direct execution after screening output is stable and assumptions are version-locked.
750 watt hub motor number of magnets checker anchor
Use this anchor for direct tool access in internal SOP and QA handoffs.
FAQ for decision intent
Magnet count and winding basics
Control and thermal decisions
Decision, risk, and next action
Final CTA: move from checker result to engineering execution
Share your target speed map, thermal assumptions, and constraints. We can convert this stage-1 screen into supplier-ready validation tasks.
Stage1c self-heal gate status
Current local gate snapshot for this route. Update these counts after each SEO/GEO verification loop.
blocker
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medium
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