Molypermalloy sends clear signals One of the most important innovations in communications history occurred when telegraph cable designers incorporated loops of wire wound around iron cores into their cables. This “simple” innovation evolved into inductors wound around Molypermalloy Powder cores, which are omnipresent in electronic devices on earth and in space. The Law of Unintended Consequences English electrical genius Oliver Heaviside states that: “actions sometimes produce developed a mathematical expression unexpected outcomes.” While the “law” known as the “Heaviside Condition”. is usually cited for unexpected negative He showed how to greatly increase the outcomes, it also applies to unexpected clarity of messages transmitted over long positive outcomes. A good example cables by coiling each wire pair in the is the invention and development of the cable around a circular magnetic core loading coil for electronic circuits. at regular intervals. This innovation The loading coil owes its existence to eliminated time delays and distortions a mathematical analysis aimed at in the signal, permitting much higher understanding why telegraph signals transmission rates. The loading coil (so became unintelligible after traveling long named because the coil “loaded” the Loading Coils from 1900 (upper right) to distances. Years of research and circuit with inductance) was born! 1927 (lower left). © AT&T Archives and History development in communications theory, Center CC BY-NC-SA 3.0 (www.ethw.org/ circuit design and materials science In 1899 AT&T engineer George Campbell Telephone_Transmission) drove the evolution of loading coils. One tested his own mathematical analysis result was Molypermalloy Powder (MPP) of loading coils. He demonstrated that cores for the coils. Today MPP cores a telephone transmission line loaded with lines was called “Pupinizing” the lines. play irreplaceable roles in myriad devices coils could transmit clear voice signals Ironically, Campbell lost the patent in automobiles, trains, wristwatches, twice as far as unloaded telephone priority battle because he waited to cell phones, computers, and electronic- transmission lines. This led to considerable file until after completing his experiments. equipment chargers. cost savings over the iron-clad copper Pupin himself had neither built coils wire technology of the day. Around the nor demonstrated the concept as The Queen illustrates the problem same time, Columbia University professor Campbell did. Mihajlo (Michael) Pupin received a The first successful (and short-lived) patent for a similar concept in priority to Permalloy cable transatlantic telegraph cable began Campbell’s application. As a result, operation in 1858. Soon after its loading coils became known as “Pupin Other people were also working on commissioning, the UK’s Queen Victoria coils”, and adding coils to transmission improving transmission quality at that › used it to send US President James Buchanan a 98-word message that took 16 hours to complete. The long trans- mission time was necessary because the cable distorted the signal when Insulator the telegrapher sent more than a few Permalloy loading tape words per hour. Heaviside paves the way When the telephone came on the scene Copper core conductor in the mid to late 1800s, communication cables had to carry a spectrum of frequencies instead of just the telegraph’s “dahs” and “dits”. This made transmission Permalloy-wrapped cable for undersea telecommunications. © SpinningSpark CC BY-SA 3.0 fidelity even more important. In 1887, (https.en.wikipedia.org/wiki/permalloy) Excerpt from MolyReview 2/2016 1 time. Danish engineer Carl Emil Krarup exposed to high currents. They excel in and renewable energy/green technology had the idea to wrap copper cable wire high-precision applications that must markets. tightly with iron wire (inventing the operate under a wide temperature range “Krarup cable”) in order to meet the with minimal loss in properties. They MPP cores in space Heaviside condition. Unfortunately, his can store large amounts of energy, design still required loading coils in making them ideal for applications such Filters with toroidal cores played an long transmission lines. AT&T therefore as chokes that block higher-frequency important role in the early stages of space searched for a material with higher AC currents in DC circuits and power exploration, and still do today. MPP cores magnetic permeability than iron. In 1914, inductors that maintain a steady current replaced much heavier cores in satellite Gustav Elmen discovered Permalloy, a in a circuit that experiences voltage or and rocket communications components, magnetic 80% Ni - 20% Fe alloy. Around current fluctuations. reducing both size and weight. These 1915, Elman and Bell Laboratories reductions translated to increases in scientists Oliver E. Buckley and H. D. Today MPP is made by both the tradi- payload capacity and significant cost Arnold greatly improved the transmission tional ingot casting/hot rolling/grinding/ savings. MPP cores reduced the total core speed of wrapped submarine cable. screening process and by powder weight in one vehicle from 2.1 kilogram atomization. Cores are compacted from to 0.009 kilogram with an attendant The design was tested in Bermuda in MPP using high pressure. They are increase in fidelity of communications and 1923, and the first Permalloy-wrapped then annealed, covered with insulation, data transmission. One early telemetry telegraph cable was placed in service and wound with wire to form finished system employed 23 filters and auxiliary connecting New York City and Horta coils. MPP cores are produced in many equipment weighing a total of 94 kilogram. (Azores) in 1924. Permalloy wrapping shapes and sizes dictated by the Similar equipment using sub-miniature increased the cable’s transmission speed requirements of specific applications. and micro-miniature components, some from 40 to 400 words per minute. Toroidal (donut-shaped) cores are the with MPP cores, reduced the system most common; they are available weight by 99.7% to 315 grams. Molypermalloy and the MPP core with outside diameters that range from only a few mm to over 160 mm. Today, NASA engineers trust the well- During the early 20th century, loading established reliability and stability of coils found new applications in power The versatility of coils with MPP MPP cores for designs that have traveled supplies and filters to eliminate current cores justifies their higher price; they are throughout the solar system. MPP cores spikes and circuit noise. Designers soon found in microelectronic components, have been used on over 40 missions, needed new magnetic core materials to inductors, power supplies, transformers including those to Jupiter, Saturn and optimize the coils’ properties for specific and electronic filters. They serve industrial, Mars. › applications. aerospace, commercial, governmental, In the 1940s, researchers discovered that adding 2% molybdenum to Permalloy yielded a material with the lowest signal losses available at the time. Over the years it evolved to include alloy variants with as much as 5% Mo. Coils with cores made from “Molypermalloy Powder” (MPP) were higher quality, smaller, lighter, and more tolerant of temperature extremes than coils made with unmodified Permalloy. MPP set the standard for high-quality powder cores, a standard that stands today. MPP cores have several advantages: They have high stability and high electrical resistance. They have low magnetic hysteresis (i.e. they demagnetize readily when the magnetic field changes), thereby minimizing heating and energy loss. Bottom view of the 275 watt power converter developed by Battel Engineering for the SAM instrument on the Mars Curiosity rover. The converter has 15 isolated power outputs for operating the three They strongly resist current fluctuations scientific sensors comprising the instrument. Seven of the seventeen MPP cores used in the power after magnetization, especially when supply are visible on the right half of the picture (boxed). © Battel Engineering Excerpt from MolyReview 2/2016 2 Consortium scientists are now analyzing Cassini’s trove of data. So much data is available that many more years will pass before they finish their work. If molecular hydrogen and other complex organic molecules are identified, it might mean life is present on a neighboring planet! It is a testament to the creativity and perseverance of generations of engineers and technologists that a discovery intended to enhance the quality of tele- graph and telephone cable transmissions has helped to take humankind to A rendering of the Cassini-Huygens spacecraft as it flies by Saturn. the far reaches of our solar system. Coils © NASA/JPL-Caltech/Space Science Institute with MPP cores helped to enable this progress because of their unique and A spacecraft with superhuman Titan and Saturn’s icy moon Enceladus. versatile combination of properties. MPP senses! Scientists hope that the INMS will identify cores already touch our lives here on molecular hydrogen present in plumes Earth in a multitude of ways, and may In one of the most ambitious missions of Enceladus, which are 90% water help to find life on other planets. yet to deep space, the NASA/ESA/Italian vapor. With Cassini’s mission extended (Robert Bukk, John Shields) Space Agency consortium launched to 2017, multiple fly-bys of both Titan and the Cassini-Huygens spacecraft in Enceladus will occur and even more data IMOA gratefully acknowledges the assistance October