FeNi Powder Cores for Telecom Power Systems

Telecom power is conservative by design. Equipment at a cell site or access cabinet is expected to run for years with limited maintenance, across temperature ranges that would be considered extreme in a data center, and often with passive or fan-assisted cooling only. The magnetic components inside those supplies inherit the same expectations.

The 48 V DC plant and where magnetics appear

Most telecom infrastructure operates from a nominal 48 V DC bus backed by a battery string. AC arriving at the site is rectified onto that bus, and equipment then converts from the bus to the voltages its own electronics need. Every conversion boundary involves magnetics: the rectifier output stage, the DC-DC converters feeding radio and control equipment, and the filtering that keeps switching noise off the DC bus.

What makes telecom power different

• Wide ambient range, including outdoor cabinets exposed to seasonal extremes
• Long service intervals, favouring designs with generous thermal margin
• Battery-backed bus carrying large fault currents and load transients
• Passive or limited forced cooling in many enclosure types
• High availability expectations, so redundancy is common and parts run continuously

Engineering requirements for telecom magnetics

Because the bus is battery-backed, its voltage moves with state of charge and load. Inductors in the converters fed from that bus must hold their value across the range without saturating, at whatever temperature the cabinet reaches.

• Inductance stability across the battery voltage range
• Sustained current capability with margin for transient load steps
• Temperature behaviour across the full cabinet ambient range
• Low radiated field, since control and radio electronics sit close by
• Mechanical robustness against vibration and thermal cycling

The role of the magnetic component

In each converter stage the inductor stores energy during part of the switching cycle and releases it to the output, while shaping the ripple current that reaches the bus. Where present, the transformer provides isolation and voltage transformation. Core material determines how much energy can be stored in a given volume, how far inductance moves with load, and how much loss appears as heat.

Why FeNi powder cores are considered for telecom power

FeNi powder cores combine a distributed air gap with high saturation flux density, which suits inductors carrying significant DC current. Because the gap is distributed, inductance declines gradually as bias increases, so the converter keeps a predictable ripple characteristic at full load rather than approaching a sharp saturation point.

The absence of a discrete gap also reduces fringing flux. In a cabinet where conversion equipment shares space with sensitive electronics, that is a practical advantage rather than a theoretical one.

Where ferrite is used instead

Rectifier and DC-DC conversion stages typically switch at high frequency, which is ferrite territory: low-loss grades keep conversion efficiency high. Ferrite is also the conventional choice for the isolated transformer function, where high permeability and tight coupling matter more than stored energy.

A telecom power system therefore uses both material families, assigned by function rather than by preference.

Design considerations

• Operating frequency of each conversion stage
• Continuous and peak current through the inductor
• Required inductance at full bias across the battery voltage range
• Core loss at the ripple frequency and flux swing
• Hot-spot temperature at worst-case cabinet ambient
• Footprint, height and mounting method
• Winding construction and its contribution to total loss

Application examples

• Rectifier output filtering on a 48 V DC plant
• DC-DC converters feeding radio units and baseband equipment
• Battery interface and charge-control converters
• Remote radio head power supplies
• Small-cell and access-cabinet power modules

Custom development for telecom power

Telecom platforms carry long qualification cycles, so magnetic components are often developed for the platform rather than selected from a catalogue. That work typically covers core geometry and permeability grade, winding design, sample evaluation at the real operating point, and a supply plan matched to the platform lifetime.

See What Are Powder Cores? for the material families, Ferrite Cores for High-Frequency Transformers for the isolation stage, and the High Flux Cores Guide for FeNi grade data.

Frequently Asked Questions

What magnetic cores are used in telecom power systems?

Both ferrite and powder cores, assigned by function. Ferrite typically serves the high-frequency rectifier and conversion stages and the isolated transformer, while powder cores such as FeNi are considered for high-current energy-storage and filtering inductors.

Why does the 48 V bus matter for inductor selection?

The bus is usually battery-backed, so its voltage varies with state of charge and load. Inductors in the converters fed from that bus must hold inductance across the full range without saturating, which makes DC bias behaviour a primary selection criterion.

Are FeNi powder cores suitable for outdoor telecom cabinets?

They can be considered where the inductor must hold inductance under heavy DC bias and tolerate elevated ambient. As with any material, suitability depends on the specific operating point, so permeability and loss data should be evaluated at worst-case cabinet temperature.

What should engineers consider when selecting a telecom power inductor?

Switching frequency, continuous and peak current, required inductance at full bias across the battery voltage range, core loss at the ripple condition, hot-spot temperature at worst-case ambient, and the available footprint and height.

Why is low radiated field important in telecom equipment?

Power converters in a telecom cabinet share space with radio and control electronics. Cores with a distributed air gap avoid the fringing flux a discrete gap produces, reducing the stray field nearby sensitive circuits must tolerate.