Space-Optimized HF Litz Wires for Inductive Proximity Switches
Maximizing the Q-Factor
PACK LitzWire developed a geometrically optimized HF litz wire for a sensor manufacturer that maximizes the copper fill factor despite limited installation space. By targeted reduction of insulation layers, the quality factor (Q) of the resonant circuit could be significantly increased, enabling more powerful sensors with the same or reduced size.
The Application
Inductive proximity switches operate without contact and are based on an electromagnetic resonant circuit consisting of a coil and a capacitor. The quality of this system is largely determined by the quality factor (Q-factor). The coil generates an electromagnetic field that forms the active detection area of the sensor.
If an electrically conductive object (damping material) enters this field, eddy current losses occur. These extract energy from the resonant circuit, which reduces the oscillation amplitude and changes the Q-factor. The evaluation electronics detect this change and trigger the switching process.
The Challenge
The trend in sensor technology is towards ever more compact designs with constant or increased switching distance performance. For the coil, this means:
- Limited winding window: The physically available space for the winding is becoming smaller and smaller.
- Quality factor (Q): To achieve high sensitivity and range, the ohmic resistance of the coil must be minimized and the quality maximized.
- Conflicting goals: Standard litz wires often have a ratio of copper to insulation (lacquer and covering) that is unfavorable for very small components. Too much insulation material "wastes" valuable space in the winding window that would be needed for current-carrying copper to maintain the Q-factor.
Compact toroidal coil made of fine copper litz wire for use in inductive proximity switches. The precise winding enables reliable detection, high repeatability, and stable electrical properties with limited installation space.
Support from PACK LitzWire
To resolve this conflict of objectives, PACK LitzWire analyzed the relationship between insulation structure and copper cross-section together with the customer. The solution lay in a customized litz wire construction that reduced the outer diameter to an absolute minimum:
- Reduced varnish application: Instead of standard enameled wires, individual wires with an optimized, thinner varnish layer were chosen, which nevertheless ensured the necessary internal insulation against the occurring voltages.
- Adapted silk insulation: The textile covering (silk/nylon), which is necessary for mechanical stability and self-bonding processability, was adjusted in its thickness and type to take up less volume.
- Litz wire design: By precisely coordinating these parameters, the outer diameter of the overall litz wire could be reduced without reducing the number of individual wires or their cross-section.
Result
The special litz wire developed by PACK LitzWire enabled a significant increase in the copper fill factor in the given winding window.
- Performance increase: Due to the higher copper content, the Q-factor of the coil increased, which improved the sensitivity and range of the sensor.
- Miniaturization: The customer was able to achieve the required performance in a smaller component size, as the winding window was used more efficiently.
- Process reliability: Despite the thinner insulation, the litz wire remained mechanically robust enough for automated winding processes.
RUPALIT® Plus
RUPALIT® Plus offers reinforced electrical protection for demanding high-voltage applications while optimizing HF losses. The integrated multi-layer insulation allows for space-saving designs without compromising safety.
Technical questions deserve precise answers.
Would you like to coordinate specifications or request a sample production? Our specialist departments will advise you directly – competently, bindingly, and reliably.
Product Manager
Internal sales team