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Glossary of terms for the magnetics industry Select a letter: A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z M Mag amp (Magnetic Amplifier) A device that utilizes a square loop core material to provide a series impedance. The impedance is switched off at a predetermined time during a voltage pulse. Magnetic Circuit The combination of magnet, permeable flux carriers and air gaps through or around which the magnetic flux path passes. Magnetic Energy The product of the flux density (B) in a magnetic circuit and the (de)magnetizing force (H) required to reach that flux density. See Energy Product. Magnetic Flux A contrived but measurable concept that has evolved in an attempt to describe the "flow" of a magnetic field. Unlike electric current where there is an actual flow of electrons, a magnetic field is the result of the energy state of a series of magnetic domains. Conceptually, one could imagine that the sequential change of energy state as the result of an applied field represents a "flow". Magnetic Line of Force An imaginary line representing a magnetic field, which at every point has the direction of the magnetic flux at that point. Flux is a vector quantity having both magnitude and direction. Magnetic Path The route magnetic flux follows in a magnetic circuit. Magnetic Path Length The length of the closed path that magnetic flux follows around a magnetic circuit. Ampere's Law determines it. For a toroidal (ring-shaped) powder core, an effective path length is defined to account for the decrease in flux density from inside diameter to outside diameter. The path length is approximately the average circumference of the ring. Magnetizing Force or Field (H) An applied magnetic field used to drive another material to a condition of being magnetized. It may be applied by current through a coil of wire or by using permanent magnets to generate the applied field. By Ampere's Law, the MKSA unit of magnetic field (magnetizing force) is the ampere-turn per meter. The CGS unit of magnetizing force is the oersted. One oersted is equivalent to 1000/(4π) or 79.58 ampere-turns per meter; one kOe = 0.0796 kA/m. Magnetometer Same as flux gate magnetometer. Magnetomotive Force Most commonly produced by a current flowing through a coil of wire where its magnitude is proportional to the current, and to the number of turns. The cgs unit of magnetomotive force is called a Gilbert and is defined by the equation:
Magnetostriction The expansion and contraction of a magnetic material with changing magnetic flux density. The saturation magnetostriction coefficient has the symbol λs. It is change of length divided by original length (a dimensionless number) and is measured at the saturation flux density. Magnetostriction causes audible noise if the magnetostriction is sufficiently large and the applied field is AC and in the audible frequency range, e.g., 50 or 60 Hz. Magnet Wire Copper or aluminum wire with electrical insulating material applied to the surface to prevent continuity between adjacent turns in a winding. Mandrel The piece that defines the shape and size of the "window" in a tape wound product when it is manufactured. This includes tape and silectron cores. Manganese-Zinc Ferrites A soft magnetic material used in powder cores and characterized by very low eddy current loss. Used for transformer and inductor cores. Compared to nickel-zinc ferrites, they have higher saturation flux density but with greater loss with high frequency current. Maximum Energy Product (BHmax) The product of Bd and Hd which yield a maximum. See also, "BHmax". Maxwell The unit of magnetic flux in the cgs electromagnetic system. One maxwell is one line of magnetic flux. Mean Length Turn The average length of a single turn in the winding of the device. Mean Magnetic Path Length The path the average flux in a magnetic structure follows. In a toroid, this is approximately the average circumference. MHz 1,000,000 Hz (MegaHetrz) Mil 0.001 inch. One thousandths of an inch; 0.0254 mm. MKSA System Meter-Kilogram-Second-Ampere system. In 1960, the Eleventh General Conference on Weights and Measures redefined some of the original metric units and expanded the system to include other physical and engineering units. The expanded system is called Le Système Internationale d'Unités, abbreviated SI. It is one of two commonly used systems of units for measuring electromagnetic quantities. The other is the CGS System, which is also the older. The advantage of the MKSA (SI) system is that the practical units for measuring current and voltage are the same as the ones used in Faraday's and Ampere's Laws. In contrast, for example, the CGS system employs "statvolts" and "abamperes" which are not the same as the volts and amperes measured by normal test equipment. MMF Magneto-motive force. MMF Drops The portions of a magnetic circuit that "consume" the applied MMF. MPP cores Molybdenum Permalloy Powder cores which are pressed from powder made of 81% nickel, 2% molybdenum and 17% iron. Multifilar Winding A winding technique where a single turn consists of two or more stands of magnet wire operating in parallel. This reduces some of the second-order effects associated with a single strand of wire. Typical would be a bifilar, trifilar, etc. Mumetal Sometimes used to describe Permalloy (especially in Europe); strictly speaking, a 65% nickel alloy. Please send all web related questions/comments to the Webmaster. TOP | BACK | HOME | HELP | MAP | CONTACT |
