Why are Q measurements variable when testing an inductor with Litz wire?
Litz wire is stranded wire with individually insulated conductors (forming a bundle). It is intended to reduce the effects skin depth at high frequency. There are multiple strands of insulated wire electrically insulated from each other. Ordinarily the strands are twisted or woven.
Q is a measure of coil losses as follows
Q = reactance/resistance
When testing Q with a Litz wire the reactance may be quite complex due to its construction. It is advisable to characterize the coil (sweep over frequency) to determine how the Q value varies with frequency.