Common-Mode Choke

Product Specifications

Technical details and manufacturing context for Common-Mode Choke

Definition

A common-mode choke is a passive electronic component used in the Magnetics Module to filter out unwanted high-frequency noise. It presents high impedance to common-mode signals while allowing differential-mode signals to pass through with minimal attenuation. This component is essential in reducing electromagnetic interference (EMI) in various electronic systems, particularly in power supplies, data lines, and signal circuits. The choke consists of two or more windings on a common magnetic core, typically made of ferrite material. The windings are arranged so that differential currents create opposing magnetic fields that cancel, resulting in low impedance for the desired signal. Conversely, common-mode currents generate additive magnetic fields, creating high impedance that blocks the noise. This behavior is achieved through magnetic coupling between the windings, which effectively blocks common-mode currents while allowing differential currents to flow unimpeded. Common-mode chokes are characterized by parameters such as inductance, rated current, DC resistance, impedance at 100 MHz, rated voltage, operating temperature, insulation resistance, dielectric withstanding voltage, tolerance on inductance, operating frequency, humidity range, and weight. These parameters are provided as typical ranges and must be verified for specific models and applications. The materials used include ferrite cores, copper wire, and insulation material. It is important to consult the manufacturer or supplier to confirm model-specific values and compliance with relevant standards. The choke operates within specified environmental conditions, and proper selection requires consideration of the circuit's operating frequency, current, voltage, and impedance requirements. Regular inspection for physical damage, overheating, or insulation breakdown is recommended to ensure reliable performance.

Working Principle

The common-mode choke utilizes magnetic coupling between windings to create opposing magnetic fields for common-mode currents, effectively blocking them while allowing differential currents to flow unimpeded. When common-mode currents flow in the same direction through the windings, the magnetic fields add, resulting in high impedance that suppresses the noise. Differential currents, flowing in opposite directions, produce opposing fields that cancel, resulting in low impedance and minimal signal attenuation. This principle enables the choke to filter out common-mode EMI without affecting the desired differential signal.

Common Materials

Ferrite Core, Copper Wire, Insulation Material

Technical Parameters

Parameter	Typical range	Notes & selection driver
Inductance	0.5–100 mH	Typical range for common-mode chokes
Rated Current	0.5–10 A	Continuous current rating
DC Resistance	0.01–2.5 Ω	Max DCR at rated current
Impedance at 100 MHz	50–2000 Ω	Common-mode impedance
Rated Voltage	50–500 V AC	Maximum working voltage
Operating Temperature	-40–125 °C	Ambient temperature range
Insulation Resistance	≥100 MΩ	Between windings at 500 V DC
Dielectric Withstanding Voltage	500–3000 V AC	Between windings for 1 minute
Tolerance on Inductance	±20 %	Standard tolerance
Operating Frequency	10–1000 kHz	Typical switching frequency range
Humidity Range	20–90 % RH	Non-condensing
Weight	5–200 g	Typical for various sizes

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

Components / BOM

Ferrite Core Part
Provides magnetic path for flux coupling and determines inductance characteristics

Material: Ferrite
Copper Windings Part
Conduct electrical current and create magnetic fields

Material: Copper
Bobbin Part
Supports and insulates windings from core

Material: Plastic
Terminals Part
Electrical connection points for circuit integration

Material: Copper Alloy

Application & selection

Application Fit & Sizing Matrix

Operational Limits

pressure:	Atmospheric to 1 atm (standard), hermetic sealing required for pressurized environments
other spec:	Current rating: 0.1A to 100A, inductance range: 1μH to 100mH, impedance at frequency: 10Ω to 10kΩ @ 100MHz
temperature:	-40°C to +125°C (operating), -55°C to +150°C (storage)

Media Compatibility

✓ PCB-mounted electronics (power supplies, data lines) ✓ Motor drive circuits (inverters, VFDs) ✓ Communication interfaces (USB, Ethernet, CAN bus)

Unsuitable: High-vacuum or corrosive chemical environments without proper encapsulation

Sizing Data Required

Required common-mode impedance at target frequency (e.g., 100Ω @ 100MHz)
Maximum continuous current rating of the circuit
Physical size constraints and mounting method (through-hole vs. surface-mount)

Risk, maintenance & compliance

Reliability & Engineering Risk Analysis

Failure Mode & Root Cause

Insulation breakdown

Cause: Thermal stress from overcurrent or high ambient temperatures degrading insulation materials, leading to short circuits between windings.

Core saturation and overheating

Cause: Excessive DC bias or high-frequency current beyond design limits causing magnetic core saturation, resulting in reduced inductance and thermal runaway.

Maintenance Indicators

Audible buzzing or humming noise indicating loose windings or core vibration
Visible discoloration, charring, or bulging of the choke body signaling thermal damage

Engineering Tips

Implement thermal monitoring with infrared imaging during routine inspections to detect hotspots before failure
Ensure proper derating according to manufacturer specifications for ambient temperature and current load to prevent core saturation

Indicative industry ranges for design and RFQ preparation. Confirm the exact figures and applicable standard with the manufacturer before specifying.

Compliance & Manufacturing Standards

Applicable Standards

IEC 60939-1:2010 (Passive filter units for electromagnetic interference suppression) ANSI C83.22-2002 (Specifications for RF and Microwave Filters) DIN EN 60939-1:2016 (Passive filter units for electromagnetic interference suppression)

Quoted from the published standard.

Manufacturing Precision

Inductance tolerance: +/-20% at rated current
DC resistance tolerance: +/-10% at 25°C

Quality Inspection

Impedance vs. Frequency Test (per IEC 60939)
High-Potential (Hi-Pot) Dielectric Withstand Test

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

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Common-Mode Choke

12 companies list this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Coilcore

Guangzhou, Guangdong, CN

Also makes: Inductor/Transformer, Current Transformer, Power Transformer and 4 more