Gallery
Custom Inductors in Production
Custom Inductors
From 200-turn bobbin coils on 18 AWG copper wire to 1,500-turn toroidal windings on 34 AWG, we manufacture custom inductors for power electronics, current sensing, EMI filtering, and industrial control applications. Ferrite, silicon-iron, and 1J85 permalloy cores. DCR tolerance to ±5%. Every unit tested.
Toroidal Inductors
A toroidal inductor is wound on a donut-shaped core. The closed magnetic path contains nearly all flux within the core itself, which reduces radiated EMI, increases inductance per turn, and delivers a smaller footprint at a given power rating.
We wind toroidal coils with even distribution across the full 360 degrees of the core, maintaining consistent tension turn by turn. This produces uniform magnetic field distribution, eliminates localized hot spots, and delivers repeatable DCR within your specified tolerance.
Core Sizes (OD)
0.800" to 2.250"
Turn Counts
200 to 1,500
Wire Gauges
26, 34 AWG
Core Materials
Ferrite, Si-Fe, 1J85
Advantages
Applications
Production Reference
We currently manufacture six toroidal product lines for NK Technologies (San Jose, CA), delivering over 150,000 cores since April 2025 with zero rejected lots. Turn counts from 750 to 1,500 on silicon-iron and 1J85 cores, using 26 and 34 AWG copper and nickel magnet wire.
Specifications
| Parameter | Range |
|---|---|
| Core OD | 0.800" to 2.250" (20.32 mm to 57.15 mm) |
| Core ID | 0.551" to 1.750" (14.00 mm to 44.45 mm) |
| Core Height | 0.256" to 0.500" (6.50 mm to 12.70 mm) |
| Core Materials | Ferrite, Grain-Oriented 3% Silicon-Iron, 1J85 Permalloy |
| Wire Gauges | 26, 34 AWG copper; 34 AWG nickel |
| Wire Insulation | Single-coat enamel, 155°C (Class F) |
| Turn Counts | 200 to 1,500 (multi-lap winding available) |
| Winding Distribution | Even, 360-degree coverage |
| DCR Range | 6.47 to 39.15 ohms |
| DCR Tolerance | ±5% to ±15% |
| Lead Length | 1.25" to 3.0" (31.75 mm to 76.2 mm) |
| Lead Tinning | SN100 lead-free solder, 1/8" to 1/4" |
| Tape | Yellow Mylar, 3M Type 74, 1/2" width |
| Core Coatings | Epoxy (0.015" thickness), Powder Coat |
| Compliance | RoHS, Lead-Free |
Bobbin-Wound Coils
Bobbin-wound coils use a plastic or phenolic bobbin as the winding form. Wire is wound onto the bobbin in organized layers, and the core is inserted after winding. This construction method provides easy, repeatable termination and efficient use of the winding window for lower turn counts.
Bobbin winding is well-suited for applications where consistent lead placement, automated assembly, and cost-effective production at volume are priorities. We wind single-layer and multi-layer configurations with precise layer insulation between windings.
Wire Gauge
18 AWG
Turn Count
202 turns
DCR
0.320 ±15% Ω
Solder
SN100 Lead-Free
Advantages
Applications
Specifications
| Parameter | Range |
|---|---|
| Wire Gauges | 18 to 34 AWG copper magnet wire |
| Wire Insulation | Single-coat enamel, 155°C (NEMA MW80-C) |
| Turn Counts | 200 to 500 (single and multi-layer) |
| DCR | 0.320 ohms and up |
| DCR Tolerance | ±15% |
| Lead Length | 3.25 mm ±0.05 mm (custom lengths available) |
| Termination | SN100 lead-free solder |
| Compliance | RoHS, Lead-Free |
Gallery
Selection Guide
Both winding methods produce reliable, production-grade inductors. The right choice depends on your application requirements, turn count, current rating, and assembly method.
| Characteristic | Toroidal | Bobbin-Wound |
|---|---|---|
| EMI Performance | Low radiated EMI (closed path) | Higher radiated EMI (open path) |
| Efficiency | Higher inductance per turn | Good for lower turn counts |
| Size | Smaller footprint at equivalent power | Larger footprint |
| Turn Count Range | 200 to 1,500 | 200 to 500 (cost-effective) |
| Current Capacity | 26 to 34 AWG (moderate current) | 18 AWG (higher current) |
| Termination | Flying leads | Organized pin termination |
| Assembly | Manual placement | Automated pick-and-place |
| Best For | Current sensing, EMI filtering, compact designs | Power inductors, relay coils, high-current applications |
Materials
Each core material has distinct magnetic properties suited to specific operating frequencies, flux densities, and application requirements. Here is what we use and when.
High-frequency applications above 20 kHz. Low core losses at switching frequencies. Used in EMI filters, common mode chokes, and switch-mode power supply inductors. Permeability range: 750 to 15,000. Core OD: 0.878" to 1.424".
Power-frequency applications at 50/60 Hz. High saturation flux density (1.6 to 2.0 T). Grain-oriented 3% silicon-iron in 7 mil and 9 mil strip. Used in power inductors, filter chokes, and power transformers. Core OD: 0.800" to 2.250".
Ultra-high permeability exceeding 100,000. Designed for current sensing transformers and precision measurement applications. Extremely sensitive to small currents. Epoxy coated. Core OD: 0.800" to 1.550".
Applications
Filter chokes and power inductors for AC/DC and DC/DC converters. Linear and switch-mode topologies. Silicon-iron and ferrite cores sized for your power rating and ripple current requirements.
Toroidal current transformers on 1J85 permalloy cores. 750 to 1,500 turns of 34 AWG wire for sensitive current measurement in industrial power monitoring systems and energy metering equipment.
Output filter inductors and EMI chokes for variable-frequency drives. Silicon-iron toroids sized to handle the harmonic content and ripple currents generated by PWM inverter stages.
Power supply inductors and EMI filters for medical devices. RoHS compliant, lead-free construction. Documented quality processes and full lot traceability for regulatory compliance.
EMI filter inductors and common mode chokes for telecom infrastructure. Ferrite cores selected for consistent impedance at operating frequencies. Compact toroidal form factors.
Filter inductors for solar inverters, wind turbine converters, and battery management systems. High-current silicon-iron toroids for energy storage and grid-tied conversion circuits.
Send us your drawings, a specification sheet, or a description of what you need. We respond to every inquiry within 24 hours.