Rotor back iron: Outer Diameter 50-300mm typical

Component Specifications

Definition

The rotor back iron, also known as the rotor yoke or rotor core, is a critical component in electric motor and generator rotors. It serves as the structural backbone that supports the permanent magnets or windings while providing a low-reluctance path for magnetic flux. This component is typically constructed from laminated electrical steel sheets to minimize eddy current losses and improve efficiency. In permanent magnet motors, the back iron enhances magnetic flux concentration and prevents flux leakage, directly impacting torque density and overall motor performance.

Working Principle

The rotor back iron operates on electromagnetic principles by providing a high-permeability path for magnetic flux generated by permanent magnets or rotor windings. It concentrates magnetic flux through the rotor structure, minimizes magnetic reluctance in the circuit, and supports mechanical forces during rotation. By completing the magnetic circuit between rotor poles, it enables efficient energy conversion between electrical and mechanical forms.

Materials

Electrical steel laminations (typically M19, M36, or M43 grades), silicon steel alloys (3-4% silicon content), cold-rolled non-oriented (CRNO) steel, occasionally soft magnetic composites (SMC) for specialized applications. Thickness ranges from 0.35mm to 0.65mm with insulation coating to reduce eddy currents.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Core Loss	<4.0 W/kg at 1.5T, 50Hz
Permeability	>1500 μr
Stack Length	20-150mm typical
Material Grade	M19, M36, M43
Outer Diameter	50-300mm typical
Stacking Factor	0.95-0.97
Lamination Thickness	0.35-0.65mm
Insulation Resistance	>100 MΩ

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 683-17, IEC 60404-8-7, ASTM A677, DIN EN 10106

Parent Products

This component is used in the following industrial products

Drive magnet assembly

The magnetic component within a magnetic coupling that transmits torque from the drive side to the driven side through magnetic fields.

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Engineering Analysis

Risks & Mitigation

Magnetic saturation leading to reduced efficiency
Eddy current losses causing overheating
Mechanical deformation under high rotational speeds
Corrosion in harsh environments
Delamination of steel sheets

FMEA Triads

Trigger: Insufficient material thickness or poor material selection
Failure: Magnetic saturation resulting in reduced torque and efficiency
Mitigation: Proper material specification with adequate saturation flux density, finite element analysis (FEA) for magnetic circuit design

Trigger: Poor lamination insulation or manufacturing defects
Failure: Increased eddy current losses leading to overheating and reduced efficiency
Mitigation: Quality control of insulation coatings, proper stacking pressure during assembly, electrical testing of completed cores

Trigger: Inadequate mechanical design or material fatigue
Failure: Structural deformation or cracking at high rotational speeds
Mitigation: Mechanical stress analysis, proper material selection for fatigue resistance, balanced rotor design

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±0.05mm for critical dimensions, ±0.1° for angular alignment, surface roughness Ra ≤ 1.6μm

Test Method

Magnetic flux density testing using gaussmeters, core loss measurement with Epstein frame, dimensional verification with CMM, insulation resistance testing at 500VDC

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Rotor back iron

Manufacturer profiles associated with Rotor back iron.

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the primary function of rotor back iron in electric motors?

The rotor back iron serves two main functions: providing mechanical support for rotor components and completing the magnetic circuit by offering a low-reluctance path for magnetic flux, which enhances motor efficiency and torque production.

Why is electrical steel laminated for rotor back iron construction?

Electrical steel is laminated into thin sheets (typically 0.35-0.65mm) to minimize eddy current losses that occur when the rotor rotates in the magnetic field. The laminations are insulated from each other to break up circulating currents, significantly improving motor efficiency.

How does rotor back iron design affect motor performance?

Proper rotor back iron design directly impacts torque density, efficiency, and thermal performance. Optimal thickness, material selection, and geometric design minimize magnetic saturation, reduce losses, and prevent excessive heating during operation.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Rotor back iron