Calculate rotor loads and diode losses, then compare excitation architectures and evidence. EESM screening only; engineering verification required.
Editable example, not recommended ratings. Passive diode bridge; results update instantly. View results ↓
15,744.9 g
Rim speed: 92.2 m/s. Retention capacity unknown.
63.0 W
Total bridge, two conducting diodes. Switching and leakage losses excluded.
150.0 V
Pfield / Ifield; bus compatibility not assessed.
5.00 Ω
Pfield / Ifield² at the entered operating point.
Junction temperature: unknown. Open the optional thermal inputs to enter measured resistance, boundary temperature and device limit.
Engineering verification required. No retention rating, field-response prediction or safety approval. Thermal estimates use an entered lumped assembly model and exclude additional losses.
Next: prepare an engineering inquiryPublic evidence supports these decisions within the limits stated below. Engineering recommendations are screening guidance, with unknowns identified rather than inferred from product announcements.
ORNL reports laboratory operation up to 20,000 rpm and 25 A, with 96% maximum efficiency at 7 kW. Ask for the candidate design’s efficiency map, cooling conditions and durability evidence before transferring that benchmark.
Evidence & primary citations: Oak Ridge National Laboratory / IEEE.
BMW’s Gen6 figures cover the wider drive concept. They cannot be used as a brushless-exciter efficiency or cost improvement in a business case.
Evidence & primary citations: BMW Group.
The iBEE announcement targets 220–350 kW peak axle output. Size the exciter from the rotor field voltage, current and duty cycle, rather than a fraction inferred from that axle rating.
Evidence & primary citations: Valeo / MAHLE.
ZF’s in-shaft approach shows why contactless transfer can help packaging. Check shaft bore, bearing span, resolver clearance and service access before claiming a length saving.
Evidence & primary citations: ZF.
The calculator supplies kinematics. Retention also depends on mass, attachment geometry, materials, temperature and fatigue. Balancing alone cannot certify an assembly against release.
Evidence & primary citations: ISO.
Field inductance, available voltage and discharge path determine the transient. Agree the measurement definition and fault cases; do not derive a fixed response time from an architecture name.
Evidence & primary citations: IEC.
The tool applies kinematics and steady-state electrical identities at one operating point. The input bounds are numerical screening limits, not validated product ratings. All required inputs are editable examples.
A brushless excitation system supplies the rotating field without sliding electrical contacts. This page focuses on EESM motor screening; industrial generator excitation also needs its own regulator and grid-duty assessment. The comparisons below are engineering screening guidance, not product ratings.
Table 1: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Architecture | Decision value | What must be checked |
|---|---|---|
| Slip rings and brushes | Direct electrical access to the field; useful comparison baseline | Wear, dust containment, service interval and field control |
| Synchronous AC exciter + rotating rectifier | Established contactless arrangement for synchronous machines | Starting/low-speed supply, magnetic design and rotor packaging |
| High-frequency rotary transformer (IPT) | Carrier excitation can be independent of shaft speed | Resonant tuning, leakage, rotating electronics and EMI |
| Capacitive coupling | Alternative contactless research route | Voltage stress and dielectric/gap sensitivity; no readiness ranking established here |
Evidence & primary citations: Oak Ridge National Laboratory / IEEE; IEC.
A resonant network can compensate reactive impedance, but tuning must cover the complete operating range. LCC and series compensation are candidate circuits rather than guarantees of gap-independent power.
Table 2: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Parameter | Why it matters | Evidence to request |
|---|---|---|
| Gap and runout | Change coupling and leakage inductance | Tolerance stack and operating gap sweep |
| Carrier frequency | Affects magnetic, switching and EMI losses | Measured loss and emission maps |
| Resonant components | Tolerance and temperature shift tuning | Worst-case circuit analysis and bench sweep |
| Zero speed | Startup requires a viable field supply | Stationary transfer and startup demonstration |
Evidence & primary citations: Oak Ridge National Laboratory / IEEE.
The tool assumes a passive full bridge carrying approximately continuous DC current. Two devices conduct in series, so total bridge conduction loss is approximately 2 × VF × I. VF must represent the actual operating current and temperature.
Table 3: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Model element | Included here | Missing information |
|---|---|---|
| Diode conduction | Total bridge loss at one operating point | Current waveform and device curve across temperature |
| Switching and reverse leakage | Excluded | Frequency, reverse voltage and device data |
| Active MOSFET rectification | Outside this diode model | RDS(on), gate supply, timing and commutation model |
| Device stress | No voltage rating selected | Transient peak, reverse rating and derating policy |
Acceleration scales with speed squared and linearly with mounting radius. For each component, radial load is mass × acceleration. A material name alone cannot provide an allowable g rating.
Table 4: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Check | Required input | Decision |
|---|---|---|
| Radial load | Component mass, radius and speed | Use calculated acceleration in attachment analysis |
| Retention strength | Geometry, interference, material curves and temperature | Calculate assembly stresses and fatigue |
| Balance | Rotor behaviour and residual unbalance tolerance | Agree rigid/flexible rotor procedure |
| Combined tests | Hot duty, overspeed case and containment plan | Set acceptance criteria before testing |
Evidence & primary citations: ISO.
Oil flow, dry conduction and spray cooling need assembly-specific evidence. Enter a thermal resistance only if it represents the hottest junction temperature rise divided by total bridge power for the chosen installation.
Table 5: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Cooling route | Potential benefit | Trade-off and evidence |
|---|---|---|
| Shaft conduction in dry cavity | Avoids direct fluid exposure | Contact and bearing paths may constrain heat flow; measure thermal impedance |
| Hollow-shaft fluid cooling | Can bring coolant near the rectifier | Validate flow delivery, sealing, drag and material compatibility |
| External jet or splash | May share existing lubrication | Wetting depends on speed and geometry; test coverage |
| Unknown thermal resistance | No justified junction prediction | Leave optional tool fields blank and request a thermal test |
Field response requires an electrical model and a test definition. For a linear constant-RL winding driven by a voltage step from zero, τ = L/R and the 10–90% current rise is approximately 2.20τ. That simplified result does not include saturation or control limits.
Table 6: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Question | Needed evidence | Minimum next step |
|---|---|---|
| Field rise time | Inductance, hot resistance, ceiling voltage and control limits | Agree initial/final current and timing definition |
| Field decay | Stored energy (½LI²) and available discharge path | Simulate decay voltage and current |
| Inverter or exciter fault | Coordinated machine/inverter fault analysis | Review rotor energy and diode reverse stress |
| Clamp or dump circuit | Energy rating, repetition and temperature | Select protection after transient analysis |
Evidence & primary citations: IEC.
The traction DC bus and rotor DC field are different electrical nodes. Field power divided by field current gives a steady-state field voltage; it does not establish isolation voltage, transient withstand or converter turns ratio.
Table 7: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Interface | Stress to characterize | Evidence needed |
|---|---|---|
| Primary converter | DC bus variation and switching transients | Input range and surge envelope |
| Rotary air gap | Isolation, contamination and runout | Geometry and dielectric assessment |
| Rotor rectifier and winding | Induced peaks and common-mode coupling | Measured waveforms and device/insulation limits |
| Winding insulation system | Converter pulse waveform and insulation type | Applicability review and qualification plan |
Evidence & primary citations: IEC.
The following is a proposed review plan. Test methods and thresholds must be agreed with the machine owner and relevant specialists; this page does not assert compliance or testing capability.
Table 8: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Evidence package | Acceptance question | Do not substitute |
|---|---|---|
| Electrical and thermal map | Are power, efficiency and temperature measured over duty? | A single peak efficiency number |
| Mechanical dossier | Are hot attachment loads, balance and rotor behaviour covered? | A material-wide g rating |
| Insulation evidence | Do representative tests reflect the actual pulse stress? | A generic 800V label |
| Fault and endurance records | Do measured decay, cycling and environment meet agreed limits? | A component datasheet alone |
Publication dates and access date are listed in the evidence directory. These examples demonstrate different kinds of evidence; they are not a supplier ranking or comparable efficiency dataset.
Table 9: Multi-dimensional comparison matrix (horizontal scroll on mobile)
| Public example | Known | Unknown / not transferable |
|---|---|---|
| ORNL, APEC 2026 | Prototype test limits and one maximum-efficiency point | Lifetime and full production operating map |
| BMW, February 2025 | 800V drive-generation comparison | Excitation-only contribution to those gains |
| Valeo–MAHLE, October 2024 | iBEE joint-development target | Current nomination/delivery status from this announcement |
| ZF, September 2023 | Vendor in-shaft integration and length comparison | Packaging saving in a different machine |
Evidence & primary citations: Oak Ridge National Laboratory / IEEE; BMW Group; Valeo / MAHLE; ZF.
Integrating a contactless brushless exciter into an existing powertrain architecture requires careful spatial budgeting. The packaging target depends on the machine. Compare in-shaft and overhung layouts against the actual shaft, bearing and cooling envelope before claiming a length saving.
Transitioning from mechanical slip rings to solid-state brushless excitation exchanges wear friction risks for thermal, mechanical hoop stress, and electromagnetic interference challenges.
Use component masses and calculated acceleration to derive radial loads. Review attachment stresses, thermal expansion, fatigue and containment before agreeing hot spin tests. Lower radius may reduce load, but does not certify a material or joint.
Conduction loss is only part of the heat budget. Measure the hottest junction thermal path over the duty cycle. Compare dry conduction and fluid cooling with flow, sealing, lubricant compatibility and pump-power effects included.
Carrier switching can disturb position sensing. Measure common-mode paths and resolver signals before choosing shielding, filtering or grounding; shielding itself can create eddy-current heating.
Review stored field energy and fault current paths with the inverter owner. Size and test the discharge circuit against actual voltage, energy and repetition limits; a universal clamp voltage is not justified.
Brushless transfer adds converter electronics, rotating packaging and validation cost. Compare total service cost and duty requirements against a brush/slip-ring baseline. For low-speed industrial duty, assess a conventional AC exciter before assuming a traction IPT design fits.
Review detailed engineering trade-offs, sizing calculations, and sensitivity checks. These are illustrative calculations, not production case histories or validated component selections.
Application Premise: Illustrative inputs: 16,000 rpm, 55 mm radius, 4.5 kW field power, 30 A and VF = 1.05 V.
Engineering Process: The model gives approximately 15,744.9 g, 150.0 V field voltage, 5.00 Ω hot equivalent resistance and 63.0 W total bridge conduction loss.
Application Premise: Keep Example A’s speed and electrical values; move the diode centroid from 55 mm to 30 mm.
Engineering Process: Acceleration falls to approximately 8,588.1 g because radius enters linearly. Electrical voltage and bridge conduction loss stay unchanged.
Application Premise: Use 63 W conduction loss, 75°C coolant and an assumed assembly Rθ of 0.75 K/W, then compare 1.5 K/W.
Engineering Process: The simplified steady-state temperatures are 122.3°C and 169.5°C. With an entered 150°C limit, the second scenario exceeds it even before omitted losses.
Sources checked on . Reported measurements, vendor disclosures and public standard scopes are distinguished below. Calculator examples and engineering review steps are our stated derivations, not measured product performance.
Published by Magnet-Free Motor. First recorded in this repository: . Review method: check primary publication scopes, reproduce the worked calculations and verify the calculator exports. Review again by , or when cited specifications change. Contact the publisher to report a correction.
Supports: Public abstract: prototype testing up to 20,000 rpm and 25 A; maximum efficiency of 96% at 7 kW. DOI: 10.1109/APEC51134.2026.11517114.
Scope Limitation: These are reported test limits and a peak operating point, not a complete efficiency map or qualification for another design. Public abstract reviewed; full paper not independently reproduced.
Supports: BMW describes an 800V generation combining EESM and ASM options. Its 40% loss, 20% cost and 10% weight reductions compare the drive concept with Gen5 xDrive.
Scope Limitation: Corporate comparison across multiple changes; it does not isolate brushless excitation benefits or disclose a transferable rectifier design.
Supports: Development announcement for a 220–350 kW peak-power electric axle using MAHLE contactless transmitter technology with Valeo motor and inverter expertise.
Scope Limitation: Peak axle power is not rotor excitation power. This dated announcement does not establish current delivery status, service life, thermal resistance or field response.
Supports: ZF describes an inductive exciter inside the rotor shaft and up to 90 mm less axial installation space relative to common separately excited synchronous motors.
Scope Limitation: Vendor-specific packaging comparison; it is not a universal 90 mm saving or proof of identical packaging for every permanent-magnet motor.
Supports: Public scope covers balancing procedures and unbalance tolerances for rigid rotors; flexible rotor behaviour is outside this part.
Scope Limitation: Scope review only. Select the balance grade and applicable amendments with the machine owner; balancing is not retention strength or overspeed certification.
Supports: Terminology for excitation systems of synchronous rotating machines.
Scope Limitation: A definitions standard does not impose a universal sub-50 ms automotive de-excitation requirement.
Supports: Qualification and quality-control scope for converter-fed stator/rotor winding insulation systems of Type I.
Scope Limitation: Applicability and test levels require review of the actual waveforms, insulation type and assembly. The public scope is not a full compliance assessment.
It transfers power to a rotating field without sliding brush contacts. Common approaches include an AC exciter with rotating rectification and an inductive rotary transformer.
The tool screens motor rotor loads. Generator voltage regulation, grid transients and exciter sizing require a machine-specific study beyond this model.
No. EESM describes the electrically excited machine; its rotor can be supplied through contacts or a contactless transfer arrangement.
Ask for a zero-speed demonstration. A high-frequency rotary transformer can operate independently of rotation; an AC exciter needs an appropriate starting supply or arrangement.
No. They are an editable worked example. Replace them with the candidate machine’s continuous operating values.
Acceleration is only a load input. Strength and fatigue depend on the entire attachment, component masses and hot material properties.
It is total bridge conduction loss, assuming two conducting devices and approximately continuous field current. Switching, leakage and other losses are excluded.
No. An active bridge needs channel resistance, switching timing, commutation and gate-supply losses; an arbitrary multiplier is not a valid substitute.
No verified assembly thermal path or device limit was supplied. Add all three optional inputs for a scenario, or request installed thermal measurements.
No. The transfer and converter design establish the relationship. The tool derives only steady-state field voltage from entered field power and current.
No. Analyze geometry, mass, attachments, interference, temperature and fatigue, then define representative mechanical tests.
No. ISO 21940-11 concerns rigid-rotor balance. Retention strength, containment and flexible rotor behaviour need separate assessment.
No. Review stored energy, voltage limits, repetition, temperature and fault paths. Protection may require another clamp or discharge arrangement.
No. Field inductance, hot resistance, voltage ceiling, control and discharge circuitry determine the measured transient.
No. They are scoped research or vendor disclosures. Use their dated source entries and request comparable evidence for the actual assembly.
Send the downloaded brief plus the speed/duty map, field voltage/current, shaft envelope, cooling data and available test reports. Identify unknown inputs and agree the next study before requesting a quotation.
Download the screening brief and send it with your speed/duty map, shaft envelope, field requirements and available cooling data. Identify missing measurements so the next study, test scope and commercial availability can be confirmed for your project.
Before requesting a quotation: confirm required deliverables, test responsibility, acceptance criteria and schedule. This page does not certify a design or promise specific manufacturing or test capabilities.
