MANUFACTURING


Inductors: Managing saturation, temperature and AC losses


Power inductors in robot servo drives and DC-DC converters must maintain predictable inductance under high current while controlling core losses and temperature rise. Panasonic’s Metal Composite (MC) power inductors use molded construction and magnetic materials designed to provide stable electrical and mechanical characteristics. Compared with conventional ferrite inductors, MC structures can provide improved DC-bias performance, with a more gradual reduction in inductance as the magnetic material approaches saturation. Lower inductance variation over temperature can help maintain consistent converter characteristics.


Mechanical and thermal reliability are particularly relevant in industrial equipment. MC inductors can undergo demanding qualifi cation, including thermal shock cycling from -40°C to +150°C for 2,000 cycles and high-temperature exposure at +150°C for 2,000 hours.


Switching frequency introduces another loss mechanism. Skin and proximity effects increase conductor AC resistance as frequency rises, increasing copper losses and component temperature. MC inductors can exhibit a lower increase in AC resistance with frequency than comparable ferrite-based designs, helping limit losses in high-frequency switching circuits.


Resistors: Improving effi ciency and environmental robustness


Current-sense resistors directly infl uence effi ciency and thermal performance in motor- drive and power-management circuits. Reducing resistance lowers dissipation


according to P = I²R, making low-value resistors attractive for high-current measurement. Panasonic’s low-resistance current- sense resistors use long-side electrode structures, optimised resistive elements and copper-nickel alloy materials to achieve low resistance values. Reducing resistance from 10mΩ to 2.5mΩ, for example, can substantially reduce heat generation at a 4A load. Environmental reliability must also be considered. Sulfur-containing gases, lubricants


and rubber materials can cause electrode corrosion, potentially leading to open-circuit failures. Panasonic’s ERJS and ERJU anti-sulfur series address this failure mechanism through different electrode technologies. In sulfur- containing oil testing, conventional resistors can fail after approximately 100 hours, while ERJU devices demonstrated no disconnection after 3,000 hours. Gold-electrode ERJS devices showed no measurable resistance change during the same test.


Designing for the complete operating environment


For industrial robot electronics, passive components cannot be selected solely on nominal specifi cations. Effective design requires consideration of DC bias, ripple current, ESR, saturation, AC resistance, temperature, vibration and environmental exposure alongside PCB area and component count. Advanced polymer capacitors, metal composite inductors and specialised low-resistance and anti-sulfur resistors provide engineers with additional options for optimising these parameters. Selecting components according to the electrical, thermal and mechanical stresses of the application can improve power-conversion effi ciency, reduce PCB size and enhance long-term reliability - key requirements for next-generation industrial robotic systems.


SEPTEMBER 2026 | ELECTRONICS FOR ENGINEERS 33


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