Mersen, the specialist in electrical protection, operates a test centre at its site in Saint bonnet de Mure, near Lyon. The company's highly qualified experts perform more than 10,000 tests per year to verify the performance and reliability of many products such as fuses. Mersen, a world expert in electrical specialties and advanced materials for advanced industry, set up a test laboratory at its Saint Bonnet de Mure site exactly 40 years ago. The complex, with an area of 1600 square meters on 4 levels, with doors more than five meters high, houses the extensive testing and research facilities of the electrical engineering specialist.
A wide range of tests in the field of electrical safety
" The laboratory is divided into two zones ," explains Ludovic Derouen, head of high-power testing. " A first high-power testing laboratory for high short circuits and a second for low-voltage, environmental and mechanical testing." Every year, on 50 test benches, employees carry out more than 10,000 electrical, dielectric, mechanical and environmental tests. Mainly on fuses and fuse holders, such as those that protect semiconductors, cables or motors. " We are also testing all Mersen product ranges, such as laminated bus bars, surge protection devices (SPDs), power capacitors and certain products manufactured by Mersen for the railway ," adds Ludovic Derouen. " We also regularly assist external customers in their developments." For example, in the aerospace industry, Mersen is testing cables for future electric aircraft. " Another current example, for electric vehicles, we are testing pyrotechnic fuses that isolate battery packs in case of defects or crashes ."
Voltages up to 43 kilovolts
The high-power testing laboratory characterizes the cut-off power, the resistance to transient currents of the fuses, as well as short circuits with very high current gradation (di/dt), all in alternating current (AC) and direct current (DC). These high-voltage tests involve the use of high-performance equipment such as fiber optic and high-frequency acquisition measurement interfaces. The power space is equipped with five test platforms, which generate a wide range of currents and voltages in both direct current and alternating current. One of these platforms is connected directly to the 20kV (3 MVA) electrical distribution network; two others are powered by capacitor banks (high di/dt and 30 MW), the last two by internal generators (20 MVA and 400 MVA). The most powerful platform can generate voltages up to 43 kV and peak currents up to 700 kA.
Specific test bench for EV products and semiconductor projections
The Laboratory therefore has two banks of capacitors. One specifically dedicated to very low inductance electric vehicle applications. It is combined with a climatic chamber to carry out nominal voltage and current tests in difficult conditions (-40°C to 150°C). The second is dedicated to the ultra-fast protections needed for semiconductor protection. It provides up to 4 kV – 320 kA with a max di/dt of about 5 kA/μs. In addition to the usual low-voltage tests, based on AC/DC power supplies and cycling equipment, the environmental and low-voltage testing laboratory is equipped with seven climate chambers.
They are used to test components in extreme conditions (-40 to +200°C / 0 and 99% humidity) and can be combined with cycled power supplies. " In salt spray tests, for example, we examine the behaviour of air fuses with a high salt content, to simulate coastal areas," explains Ludovic Derouen. " This equipment in accelerated cycling configuration allows us to simulate the aging of products in critical situations ," adds the expert.
Independent and impartial
All the technicians working in Saint Bonnet de Mure are very experienced. The director of the laboratory, Franck Sarrus, is also responsible for Research & Development at Mersen in Europe. Does this mean that the center is part of the R&D department? " Yes and no ," replies Ludovic Derouen with a smile. Of course, the laboratory supports the R&D activity of the Mersen group, in a global context where testing resources are limited in this area. Quick and easy access to high-tech testing capabilities is therefore a very important factor and not to be underestimated for a company with a strong R&D focus like Mersen.
On the other hand, internal customers, including R&D, are treated with the same independence and impartiality as external customers, thus complying with the 17025 standard. " We test the components and report whether or not they achieve the required performance ," says Ludovic. External customers of the test center are now in the minority; more than 90% of the laboratory's capacity is currently used for internal requests. In the future, Mersen intends to offer more availabilities to the latter. "We are already ideally equipped for this next step, with all the capabilities and means necessary to meet the particular needs of our customers."
Currently, Mersen Electrical Power operates three major electrical test centers worldwide. In addition to Saint Bonnet de Mure, there is a laboratory in Newburryport (USA) and another in Terrassa (Spain). "Weare working closely with our American colleagues in Massachusetts, particularly on the UL tests," explains Ludovic Derouen: "TheAmerican and French test centres are also complementary. Both are capable of operating in direct current and alternating current but at different levels of current and voltage, thus meeting the needs of our products ."
The Saint Bonnet de Mure test center is accredited by COFRAC which ensures compliance with the ISO-17025 standard. Accreditation to the U.S. UL standard is scheduled for 2022 – 2023. "In addition to the European, Chinese and Indian markets, we are also testing products in France for the US market." With regard to potential future developments and to keep up with new market needs, such as energy storage, e-mobility markets and the future DC network, the laboratory is constantly investing in new dedicated equipment, as well as in the training of its technicians.