Arc track resistance testing is an important topic that is of interest to many in the aerospace industry. In this article we discuss the test itself, common test types, the process, and the price of the test performance.
Test methods
Among the most common test methods for arc track resistance testing are: the AS4373, MIL-STD-2223, and EN3475. There are other test methods, but they are typically proprietary test methods, such as the Boeing BMS standard. Within each of these standards there are both wet arc track resistance tests and dry arc track resistance tests. Among these standards, there are slight differences in the setup, circuit configuration, and termination conditions.
Deciding which method to use is more often driven by the end client or market. The AS4373 test method is a common test method for US military and commercial customers. The MIL-STD-2223 is applicable only to legacy systems as this test method has been superseded by the AS4373 test method.
The EN3475 method is common for the European market, and probably could be considered to be the most severe test of those presented here. That is because, unlike the other test methods discussed, the EN method has more power wires in the test sample harness.
Test Performance
Careful control of the arc track resistance test parameters ensures accurate, consistent results. Contact Lectromec to find out more about the testing services offered.
For each of these tests there is a common set of steps:
- Visually inspect received wire: This is done to find any obvious defects in the wire and wire insulation. The most common cause for defects is damage during shipping.
- Perform wet dielectric test: The wire used in the arc track resistance test is submerged in a bath and subjected to a 2.5kV dielectric test. The objective is to identify any defects in the wire insulation and remove any segments that have insulation breaches. This is an important step in that it removes the chance of falsely identifying wire damage for electrical arcing.
- Sample preparation: The wires are cut, stripped, and assembled into 7-wire harnesses. The particular lengths and configurations are identified in each specification. The wires are then bound together with lacing tape.
- Test performance: Once the harnesses are prepared, they are installed in Lectromec’s arc track resistance test system (Lectromec currently has the capability of testing three harnesses simultaneously). Depending on the particular test type, this may take as long as a week to complete. To understand where the variability in tests may come from, read Lectromec’s Understanding Unexpected Arc Track Resistance Test Results article.
- Posttest assessment: After the testing is performed, the length of the damage to each wire is measured and the number of passive wires damaged during the test is assessed via a wet dielectric test to 1.5kV. (Read our What do the Results of Arc Track Resistance Testing Mean? article for a discussion on the meaning arc track resistance test results.)
Reduced testing and cost for R&D
We offer a couple of options, which can be of particular interest to those looking to reduce costs and/or get a basic understanding of their materials performance.
As mentioned earlier, most of the arc track resistance tests require multiple trials performed at given circuit resistance values (e.g. the 0.0, 0.5, 1.0, 1.5, and 2.0 Ohms). While it is ideal that all of these tests are performed, it is possible to gain some insight into the wire performance without a full battery of tests. A reduced sample set of one or two trials per circuit resistance value can help to direct the R&D down a more viable development path.
Pricing
At this time, the pricing for arc track resistance testing is as follows:
- Full battery of 15 dry arc track resistance tests (AS4373) – $3,200
- Full battery of 15 wet arc track resistance tests (AS4373) – $4,000
- R&D reduced testing of dry arc track resistance tests – $1,200
- R&D reduced testing of wet arc track resistance tests – $1,700
Custom testing needs and changes to the test parameters (e.g. different resistance values, wire gauges, voltage, etc.) will be addressed on a case by case basis and may affect the test price. Contact Lectromec to find get a quote.
Michael Traskos
President, Lectromec
michael.traskos@lectromec.comMichael has been involved in wire degradation and failure assessments for more than a decade. He has worked on dozens of projects assessing the reliability and qualification of EWIS components. In September 2014, Michael was appointed as an FAA DER with a delegated authority covering EWIS certification.