1988 Volume 74 Issue 6 Pages 1036-1043
A new rotating transformer with flat coils of air core has been developed for eddy current flaw detector of rotating probe type. This type of transformer provides following features in comparison with conventional one with the coils of ferrite core.
(1) Readiness to design and manufacture larger transformers with excellent homogeneity
(2) Light weight
(3) Low cost
Sufficient transmission efficiency was obtained with 20 turns for the air core coil of 200mm in inner diameter when the exciting frequency was 32kHz.
In this case the voltage transmission efficiencies were about 50% at the exciting side and 67% at the receiving side and the overall efficiency was about 34%. These values are large enough to guarantee the S-N ratio for the flaw detection. The test run of flaw detection on a reference block showed that the S-N ratio in the case of using these transformers were equivalent to that of the direct wire connection without transformer.
