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HOME : TECHNOLOGY CENTER : REFERENCE MATERIALS : GLOSSARIES : P 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 P Permalloy 4-79 Molybdenum Permalloy. A 4% molybdenum, 79% nickel, 17% iron alloy used to make tape-wound and laminated cores. Permanent Magnet Material Shaped piece of ferromagnetic material, which once having been magnetized, shows definite resistance to external demagnetizing forces, i.e., requires a high demagnetizing force to remove the residual magnetism. Permeability The ratio of the ability of a material to carry magnetic flux in comparison to air or a vacuum, the permeability of which is, by definition, one. Permeability, Incremental The ratio of change in magnetic flux density to change in magnetic field (magnetizing force). µ = (1/µo)ΔB/ΔH in MKSA units µ = ΔB/ΔH in CGS units The magnetic field variations are small or "incremental" and can be in addition to a steady (DC) bias field. For magnetic powder core data, "permeability" is incremental permeability unless otherwise noted. Because of the distributed air gap in powder cores, the initial permeability and incremental permeability, without bias, are essentially the same. Permeability, Initial The limit of incremental permeability as a changing unbiased magnetizing force approaches zero. Because of the distributed gap in powder cores, the initial permeability and incremental permeability without bias are essentially the same. Permeability, Normal - µ The ratio of the normal induction to the corresponding magnetizing force. In the cgs system, the flux density in a vacuum is numerically equal to the magnetizing force and, consequently, the magnetic permeability is numerically equal to the ratio of the flux density to the magnetizing force. Thus: µ= B/H Note: In a non-isotropic (anisotropic) medium the permeability is a function of the orientation of the medium, since, in general, the magnetizing force and the magnetic flux are not parallel. Permeability of Free Space µo - The permeability of a volume occupied by a vacuum. Sometimes called the magnetic constant. Free space permeability is an arbitrary constant used with relative permeability to define the magnetic field (magnetizing force), H, and account for the contribution of a magnetic material to total flux density. In the MKSA system, it has a magnitude of 4π x 10-7 and dimensions of Henries per meter. In the CGS System, free space permeability has a magnitude of 1 and no dimensions. The MKSA free space permeability was chosen so that the practical units for electrical measurements match the ones used for relating magnetic quantities to voltage and current. Permeability, Recoil The ratio of change in flux density as a function of incremental change in applied field (H) in the vicinity of H=0. It has no dimensions in either the MKSA or CGS system. µoµr = B/H in MKSA units. µr = B/H in CGS units. Permeameter An instrument used to check permeability on low-permeability cores such as MPP and powdered iron. This type of instrument is preferred over an inductance bridge because it is better suited to high-speed testing. In permanent magnet material, the instrument is used to measure, and often record, the magnetic characteristics of a specimen. Also called a hysteresisgraph. Permeance The reciprocal of the reluctance, R, measured in maxwells per Gilbert. Permeance Coefficient (Pc) Also known as the "load line" or operating point of a magnet. The Pc is affected by the dimensions of the magnet and the associated magnetic circuit. A calculation to determine the Pc of simple magnet geometries in free space can be made or tables and graphs referred to. Poles, North and South Magnetic The north pole of a magnet, or compass, is attracted toward the north geographic pole of the earth (which is actually, by definition, a magnetic south pole), and the south pole of a magnet is attracted toward the south geographic pole of the earth. The north-seeking pole of a compass or of a magnet is designated by the letter "N", and the other pole by the letter "S". The N (north) pole of the magnet will attract the S (south) pole of another magnet: unlike poles attract. Post Regulation A technique utilizing cores to regulate the "unregulated" outputs of a multiple-output switch-mode power supply. Can use a transistor or a mag amp. Pot Core A core configuration that looks like a "pot" or a cup with a center post, consisting of two halves assembled around the coil. Because of this, the core is considered to be self-shielding of stray flux (EMI). This type of core generally is available only in soft ferrites. Powdered Iron Material used in the manufacture of soft magnetic powder cores. Iron in the form of small particles is mixed with insulation and binding materials. The mixture is pressed and cured to form inductor cores. Precase Test Tape cores normally are tested after being annealed, but before being cased or epoxy coated. This permits re-annealing if the core fails the test, which could reclaim an otherwise scrap core. Primary Winding The winding in a transformer that supplies the exciting MMF to the core. Pulse Losses Core losses during pulse excitation are quite different from sinusoidal or symmetrical square wave losses. Special loss curves generally are required to determine core loss accurately. Otherwise, there are methods to approximate pulse losses from conventional loss curves. Pulse Permeability The permeability of a magnetic material when the excitation is in the form of a short-duration unipolar pulse. Pulse Transformers Transformers designed for excitation that consists of short-duration pulses repeated at a specific rate. Pure Inductors Used at all frequencies to provide an electronic circuit with inductive reactance. Please send all web related questions/comments to the Webmaster. TOP | BACK | HOME | HELP | MAP | CONTACT |
