Primary Coil: Excitation Voltage 1-10 V RMS

Component Specifications

Definition

The primary coil is a critical electromagnetic component in Linear Variable Differential Transformer (LVDT) feedback devices. It consists of a precisely wound copper conductor around a ferromagnetic core, designed to generate a stable alternating magnetic field when energized with an AC excitation signal. This electromagnetic field interacts with the movable core to produce voltage differentials in secondary coils, enabling accurate measurement of linear displacement with sub-micron precision.

Working Principle

When an AC excitation current flows through the primary coil, it generates an alternating electromagnetic field. This field induces voltages in two secondary coils positioned symmetrically around the primary. The movable ferromagnetic core alters the magnetic coupling between primary and secondary coils proportionally to its position, creating a differential voltage output that precisely indicates linear displacement.

Materials

High-purity copper wire (typically 99.9% Cu) with polyurethane or polyimide insulation, wound on a bobbin made of high-temperature thermoset plastic (PEEK or phenolic), with optional ferrite or permalloy core materials for enhanced magnetic properties.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Inductance	10-100 mH
Resistance	50-500 Ω
Wire Gauge	AWG 32-42
Winding Turns	500-2000 turns
Excitation Voltage	1-10 V RMS
Excitation Frequency	400 Hz - 20 kHz
Insulation Resistance	>100 MΩ at 500 VDC
Operating Temperature	-40°C to +150°C

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 9001, IEC 60068, MIL-PRF-39032

Parent Products

This component is used in the following industrial products

Feedback Device (e.g., LVDT)

A sensor component in servo valves that provides real-time position feedback of the valve spool to the control system.

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Engineering Analysis

Risks & Mitigation

Insulation breakdown from voltage spikes
Thermal degradation from excessive current
Mechanical damage to fine windings
Magnetic interference from nearby equipment
Corrosion of copper conductors in humid environments

FMEA Triads

Trigger: Overvoltage transients in excitation circuit
Failure: Insulation breakdown and short circuit
Mitigation: Implement surge protection devices, use reinforced insulation materials, and design with voltage derating margins

Trigger: Excessive excitation current causing overheating
Failure: Thermal degradation of insulation and increased resistance
Mitigation: Incorporate thermal monitoring, design with proper current ratings, and ensure adequate heat dissipation

Trigger: Mechanical vibration and shock
Failure: Wire breakage and winding deformation
Mitigation: Use vibration-resistant winding techniques, epoxy encapsulation, and mechanical dampening in mounting

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±0.5% of full-scale output for electrical parameters, ±2% for dimensional specifications

Test Method

Electrical testing per IEC 60529 for insulation resistance, inductance measurement using LCR meter, thermal cycling per IEC 60068-2-14, vibration testing per MIL-STD-810

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 Primary Coil

Manufacturer profiles associated with Primary Coil.

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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 happens if the primary coil excitation frequency is incorrect?

Incorrect excitation frequency causes phase shift errors, reduced sensitivity, and nonlinear output. LVDTs are designed for specific frequency ranges (typically 400 Hz to 20 kHz) to optimize magnetic coupling and signal-to-noise ratio.

Can primary coils be replaced independently in LVDT assemblies?

Primary coils are typically integrated into complete LVDT assemblies due to precise winding specifications and magnetic calibration. Replacement requires factory recalibration to maintain measurement accuracy within specified tolerances.

What maintenance do primary coils require?

Primary coils require minimal maintenance. Regular inspection for insulation damage, verification of electrical continuity, and monitoring of excitation current stability are recommended. Environmental protection from moisture and contaminants extends service life.

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.

Primary Coil