A Method for Testing Enameled Copper Wire for Surface Quality and Electrical Integrity

Author: Brian J Alexander
Lear Technical Consultant, Europe

The bead detection head is located on the wire line before lubrication and connects to an electronic console. Within the console, filtering and amplification takes place followed by an analogue to digital conversion for each detector channel. Once passed to a PC, the keyboard is used to input speed, spool length etc. The user then defines allowable beads and the allowable number that can occur within a certain window of length that typically is 30 meters. System alarms are set to alert the operator of excessive bead presence and other deterioration factors.

The signal produced can be modified or amplified by the electronic console. The machine operator feels the running wire in the way to which he has become accustomed and adjusts the Lear system to coincide with his bead decisions.

Within a very short time of introduction of this bead detection system, the industry began to request that their other major problem area, electrical breakdown through pin holes in the enamel film, or even bare wire, be tackled by Lear so that one compact detector head could monitor surface and high voltage continuity (HVC) on a continuous basis during manufacture. It has already been explained that there are no specifications defining a bead but there are specifications that relate to HVC determined off-line. [Ref 1] These specifications are based on static laboratory test on wire samples taken from earlier production. However these specifications were not related to the existing on-line HVC systems built by other companies. The anomalies in these methods of test have been described earlier. [Ref 2]. These latter systems take the wire across three pulleys that apply the test voltage, usually 1,500 volts. By the physical nature of these systems, up to 50mm of wire is simultaneously in contact with the pulleys and the test inspection rate and resolution has to be related to this length to properly count each fault and record the current level.

The approach used by Lear was to generate the high voltage used for the HVC test (400 to 3,000 VDC), within the detector head and apply this voltage to the insulation at the same point as where bead detection took place. The test footprint length along the wire for both functions is then less than one millimeter, easily meeting Lear's goals for high resolution. Combining these two test functions in one small detector led to the name Fusion system.

HVC fault current resolution is .1 micro amp and maximum bead detection sensitivity exceeds human touch. Seven years operating experience, to date, across a large segment of the industry has yielded excellent results in performance, reliability, and operator friendliness.

A round wire Fusion detector is shown in Fig 2.

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