Linear Motor Electromagnetic Interference Mitigation Methods

Overview of Technical Issues:

The electromagnetic fields generated by the current-carrying coil in the linear motor radiate outward as a harmful effect, interfering with surrounding electronic equipment and causing signal distortion and control errors, while the magnetic field generating structure insufficiently contains the magnetic flux, allowing excessive leakage beyond the working gap; the goal is to mitigate this electromagnetic interference to achieve electromagnetic compatibility and ensure reliable operation of nearby sensors and control systems.

Solution directions generated for this problem

Problem Direction 1 :

ImproveMagnetic flux leakage intensity
VS
ConstraintSystem structural complexity

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out (Extraction)
Cross-domain applicability Assess applicability
Charging device that reduces an amount of noise flowing through a charging system in a vehicle
Innovative Solution Refine solution

Bolt-on ferromagnetic flux return plates for external leakage capture

Extract leakage flux management from motor core by adding external bolt-on ferromagnetic plates
How to solve :
  • Install external ferromagnetic return plates (silicon steel M19, thickness 3–5mm, relative permeability μr≥3000) at 50cm boundary using standard M8 bolts, capturing 8–12mT leakage flux and routing it back to motor housing without modifying coil assembly
  • Position plates perpendicular to primary leakage direction, forming low-reluctance return path that intercepts stray flux before reaching sensitive equipment, reducing field to <3mT at boundary
  • Use modular plate segments (4–6 pieces) with simple bracket mounting, adding only 4 components vs. 25+ for integrated shielding, maintaining assembly part count at 16 total
Expected Effect : Leakage flux reduced to <3mT at 50cm; part count +4 only; 85% flux containment achieved; zero precision alignment required
Risk Control :
  • plate positioning accuracy affects capture efficiency
  • bolt fastening torque inconsistency causes air gaps
  • ferromagnetic saturation under peak current transients

Problem Direction 2 :

ImproveMagnetic flux leakage intensity
VS
ConstraintMotor force output

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Power transmission belt with striped surface and a striped cover fabric
Innovative Solution Refine solution

Segmented magnetic circuit with dual-zone flux management for leakage reduction

Divide magnetic circuit into high-flux working zone (air gap region) and low-leakage outer zone with independent flux paths
How to solve :
  • Install shaped pole pieces with 8mm thick sections facing the 2mm working gap to concentrate flux density at 1.2T, maintaining 500N thrust
  • taper outer sections to 2mm thickness to create high reluctance path, limiting external field propagation
  • Add segmented flux return yokes made of silicon steel (B50A400 grade, permeability ≥4000) around outer zone only, capturing 85% of the 40-50% leakage flux and routing it back through dedicated low-resistance channels parallel to main circuit
  • Apply zoned current distribution with 12A in inner coil windings (gap-facing, 80 turns) for force generation, 6A in outer windings (40 turns) for field shaping, reducing far-field leakage to 2.5mT at 50cm while preserving peak thrust
Expected Effect : Leakage field reduced to 2.5mT at 50cm (72% reduction); 500N force maintained; flux containment 87%; part count +8 components only
Risk Control :
  • pole piece alignment tolerance must be ±0.1mm
  • segmented yoke air gap <0.3mm to avoid flux loss
  • dual-zone current control requires synchronized driver

Problem Direction 3 :

ImproveMagnetic field containment effectiveness
VS
ConstraintSystem structural complexity

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out (Extraction)
Cross-domain applicability Assess applicability
Wheel mounting system
Innovative Solution Refine solution

Bolt-on external flux return yoke for passive leakage capture

Bolt-on external flux return yoke captures leakage flux
How to solve :
  • Install external ferromagnetic yoke plates (silicon steel M19, thickness 3-5mm, relative permeability μr≥5000) at 50cm boundary using standard M8 bolts, capturing the 40-50% leakage flux and routing it back to motor housing without internal assembly changes
  • Position yoke plates symmetrically around motor perimeter with 10mm air gap tolerance, no precision alignment required—plates self-align magnetically to flux paths, adding only 4 components versus 25+ for integrated shielding
  • Connect yoke ends to motor housing ground points using low-reluctance joints (contact resistance <0.5 mΩ), forming closed external flux return loop that redirects leakage back into working gap, achieving 85% containment while maintaining 500N thrust
Expected Effect : Flux containment 85%, leakage field <3mT at 50cm, part count +4 only, assembly time <15min
Risk Control :
  • yoke plate positioning deviation >15mm reduces capture efficiency
  • bolt joint contact resistance >1mΩ increases reluctance
  • silicon steel grade variation affects permeability

Problem Direction 4 :

ImproveMagnetic field containment effectiveness
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Laminated core and electric motor
Innovative Solution Refine solution

Spatially segmented magnetic circuit with dual-zone flux architecture

Divide magnetic circuit into dual zones spatially
How to solve :
  • Segment the magnetic circuit into high-permeability working zone using silicon steel laminations (0.35mm thickness, μr≥5000) surrounding the air gap to concentrate flux for 500N thrust, and low-permeability containment zone using soft ferrite rings (μr=800-1200) in outer regions to capture and redirect the 40-50% leakage flux back into the main path
  • Install flux return bridges connecting the two zones at 4 symmetrical positions around the coil assembly, each bridge 8mm wide × 15mm deep, made from grain-oriented electrical steel to guide leakage flux from outer zone back to working zone with minimal reluctance
  • Shape pole pieces with asymmetric taper geometry: 25mm thickness facing air gap tapering to 8mm at outer edge over 40mm radial distance, naturally biasing 85% of flux into working gap while limiting external field to below 3mT at 50cm boundary
Expected Effect : Flux containment 85%, leakage field <3mT at 50cm, thrust maintained at 500N, part count +6 components only
Risk Control :
  • ferrite-steel interface reluctance mismatch
  • flux bridge saturation under peak current
  • dimensional tolerance affecting flux distribution
Patsnap Eureka Solution