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Testing & Assessment

High Current Testing

Several things can go wrong when a wire or cable is subjected to an electrical current exceeding its design limitation and none of them are good. These include, but are not limited to, melting of the insulation, smoking, insulation degradation, promotion of intermetallic growth between the plating and conductor, melting of the conductor, melting of the conductor plating, and conductor embrittlement. Thankfully, if the wire/cable is being used within its temperature and current ratings, the wire should experience very little of the above phenomena. Read more

DO-160, EWIS, and EMI

Designing a circuit diagram for a system comprised of Line Replaceable Units (LRUs) is usually a straightforward process: identify the inputs and outputs of the system and connect them with wires and cables. Taking that simple high-level circuit diagram and implementing the physical design into an application can be quite difficult. This requires the proper connectors, optimized the physical routing, and ensuring negligible impact from electromagnetic interference (EMI). From an implementation perspective, it cannot be understated how much EMI can impact system performance ranging from degraded performance to make a system completely inoperable. Thankfully, there are test methods to evaluate the susceptibility of electromagnetic interference of a wire harness design. Read more

Testing the Performance of AFCBs

Arc Fault Circuit Protection has been a technology that dates back to the 1990s. Despite this not being a new technology, the breath of its implementation is still limited. The device owes its inception to arcing events that occurred on in-service aircraft. Because of these events, the wiring community sought to create wiring that was arc track resistant, and the circuit protection community sought to cut off the arcing event before too much energy was released. This has been captured in the requirements of AS5692 for AC circuit protection, and AS6019 for DC protection Read more

Galvanic Corrosion and Red Plague

Some have brushed the issue aside saying that they have never seen it, thus it is not a problem. To put the issue of red plague into perspective, a worst-case estimate suggests as much as 3% of braided silver-plated copper shields have some degree of red plague. Across the aerospace industry, this equates to millions of dollars each year in scraped products, rewiring, and maintenance actions. Read more

Unwanted Energy Storage in Cables – Dielectric Constant

A good wire insulation is more than just preventing electrical energy from leaving the conductor; there are dozens of properties that are important to its performance and usability. One of these that is easy to overlook is the wire’s dielectric constant. Read more

Insulation Resistance: Measuring Leaky Wires

Wire insulation integrity is a fundamental part of wire performance. Without it, the safety and reliability of a wire is significantly reduced. Over the years, the industry has developed dozens of insulation integrity assessment methods. Among the range of tests that exist in the world of wiring, one of the tests that is often misunderstood […] Read more

Shield Grounding and EMI Protection – Part 2

EMI, the concept of electromagnetic interference, is a relatively simple one to convey: radiated energy from other sources induces a voltage in another circuit. But like many things, the simplicity of its description belies the true complexity of mitigating it. Shielding of signal wires, wire harness shielding, shielding of power wires, induced noise studies are […] Read more

What is an EWIS Qualified Wire?

This is a question that Lectromec regularly receives. The reason for this question is that a parts-supplier or system-integrator is looking to find wires in compliance with EWIS requirements. Since there are so many ways to evaluate any component, the important question to consider is if a defined requirements list for aerospace wire exists? Here, […] Read more

Connector Failure Rates – Part #2

In Lectromec’s previous article, we introduced a basis for estimating connector failure rates. The framework utilized the failure information available from military handbook MIL-HDBK-217. In this article, we continue to review the parameters of the failure rate function and implications on how slight changes in the environment can have a dramatic impact on a connectors […] Read more

Happy Holidays from Lectromec

Lectromec’s lab did one last set of tests before the 2017 holidays. We bring you a polyimide Christmas tree powered by 270VDC. Read more