In order to compare both applications, the cross-section of HF litz wires and that of individual strands must be the same. The splitting up of HF litz wires into several individual strands with a smaller external diameter results in improved current distribution. Skin and proximity effects can thus be reduced at high frequencies.
1. Heat treatment in heating cabinet Depending on the size of the finished wound coil, this process requires a dwell time of between 5 and 30 minutes in the heating cabinet. The temperature applied should be approx. 150-160 °C, in order to achieve uniform heating of the entire winding.
2. Bonding with the aid of resistance heating by current surge
The strength of current and process duration must be adapted to suit the size of winding and dimension of individual strand used. Care is to be taken to avoid overheating the core of the winding in models with very high numbers of turns. Otherwise, in extreme cases, the soldable enamel base layer could be destroyed and interturn short circuits occur.
3. Bonding in defined hot air flow
This method consists of treating the package to be wound in a current of hot air. The temperature of this hot air flow depends on the diameter of the single strands, on the winding former and on the speed at which winding is conducted. Generally speaking, the temperatures selected should be in the 190 to 230 °C range. The hot air should only be allowed to act on the package while the winding process is in progress to prevent overheating of the winding.
Conclusion: this method pro vides the most rational production method in the majority of cases.
4. Applying enamel coating with solvents
The layer of baked enamel is applied with the aid of a suitable solvent (e.g. alcohol). It is usual for windings to be tempered subsequently in a drying cabinet to ensure that the enamel coating is thoroughly hardened. This process also removes all traces of solvent from the winding. Application of this process should thus only be considered for winding with a low number of turns.
Conclusion: this method is less recommended as there is a risk of a residue of solvent remaining in the winding. Such a residue can lead to the enamel base layer being destroyed, which can in turn produce short circuits.
Because RUPA profile wires are produced to customer specifications and can additionally be adapted to the specific type of coil former used.
Advantage: production of prototypes and patterns or modifications in design are possible within a very short time.