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| BHmax – Maximum Energy Product | The maximum product of (Bd x Hd) which can be obtained on the demagnetization curve, i.e. in the second quadrant of the hysteresis loop. |
| Bis (or Js) – Saturation Intrinsic Induction | The maximum intrinsic induction possible in a material. |
| Bi (or J) – Intrinsic Induction | The contribution of the magnetic material to the total magnetic induction, B. It is the vector difference between the magnetic induction in the material and the magnetic induction that would exist in a vacuum under the same field strength, H. This relation is expressed by the equation: Bi = B - Hem where; Bi = intrinsic induction in gauss (or tesla); B = magnetic induction in gauss (or tesla); Hem = field strength in oersteds (or kA/m). |
| Br – Residual Induction (or Flux Density) | The magnetic induction corresponding to zero magnetizing force in a magnetic material after saturation in a closed circuit; measured in gauss or tesla. |
| Carbonyl Iron | A relatively expensive iron powder used in low-permeability, high- frequency powdered iron cores. |
| Coercive Force, Hc | The value of demagnetizing force that reduces residual induction to zero. The maximum coercive force, as measured on a saturated magnet, is proportional to the remanent flux density. See “flux density.” It is expressed in oersteds or kiloAmps per meter (kA/m). |
| Coercivity, Hci or iHc | The resistance of a magnetic material to demagnetization. It is equal to the value of H where the intrinsic curve intersects the H axis in the second quadrant of the hysteresis loop. It is expressed in oersteds or kiloAmps per meter (kA/m). |
| Current Density | The amps per unit of cross-section in the conductor. |
| Curie Temperature, Tc | Tc or Tc: The temperature above which ferromagnetic materials become paramagnetic, losing substantially all of their permanent magnetic properties. Some references state materials become non- magnetic above the Curie temperature. |
| DC Bias | Direct Current (DC) applied to the winding of a core in addition to any time-varying current. Inductance with DC bias is a common specification for powder cores. The inductance decreases or “rolls-off” gradually and predictably with increasing DC bias. |
| Demagnetization Curve | That portion of the hysteresis loop which lies between the residual induction point, Br, and the coercive force point, Hc (normal curve) or Hci (intrinsic curve). Points on the normal curve are designated by the coordinates Bd and Hd. |
| Demagnetized | A material condition where a ringing AC field has reduced the remanent induction to or near zero. A ringing AC field is a continually decreasing sinusoidal field. A pulsed DC field can be used to achieve gross demagnetization, but with much effort and with residual local magnetization. |
| Electromagnet | A magnet formed by current flowing through a conductor. The electrical conductor may be wire, copper plate or strips of foil and may exist with a permeable material such as steel to conduct the field to desired |
| Ferrites | A soft ferrite material that has lower permeability with very low eddy-current loss. The common ferrites are nickel-zinc, manganese-zinc and magnesium-zinc ferrite. |
| Ferromagnetism | Ferromagnetic materials have atomic fields that align themselves parallel with externally applied fields creating a total magnetic field much greater than the applied field. Ferromagnetic materials have permeabilities much greater than 1. Above the Curie temperature, the ferromagnetic materials become paramagnetic. |
| Filter Capacitor | A capacitor, quite often used in conjunction with an inductor, that filters unwanted frequencies by storing electrostatic energy. |
| Flux | In magnetics, the magnetic field. Flux implies flow which is not the case in magnetics. That is, no one has measured a magnetic "flow". Flux is represented conceptually as "magnetic lines of force". Flux density is measured in gauss or tesla. |
| Flux 0 | In the special pulse test used to evaluate bobbin tape cores, this corresponds to Bm – Br. |
| Flux 1 | In the special pulse test used to evaluate bobbin tape wound cores, this corresponds to Bm + Br. |
| Flux Density | Magnetic (B) - The fundamental magnetic force field. “Flux” means to flow (around a current carrying conductor, for example) and “density” refers to its use with an enclosed area and Faraday’s Law to determine induced voltage. Also called the “induction field.” From Faraday’s Law, the MKSA unit of flux density is a volt-second per square meter per turn or “Tesla.” (The CGS unit of magnetic flux density is the Gauss. There are 10,000 Gauss per Tesla).Remanent or residual ~ – The flux density that remains in a magnetic material after an applied magnetic field (magnetizing force) is removed.Saturation - This is the flux density of maximum material magnetization. Magnetization (M) is the contribution of a magnetic material to the total flux density. B = µo(H+M) in MKSA units. B = H+4pM in CGS units. |
| Saturation magnetization is the maximum value of magnetization. Also,the term “saturation” is sometimes used as a reference to the decrease of permeability with increasing magnetizing force. In an inductor, this corresponds to a decrease of inductance with current. | |
| Gauss | The unit of magnetic induction, B, in the CGS electromagnetic system. One gauss is equal to one maxwell per square centimeter or 10-4 tesla. |
| Hc – Coercive Force | Equal to the demagnetizing force required to reduce residual induction, Br, to zero; measured in oersteds (or kA/m). The material characteristic of coercivity is taken as the maximum coercivity -- that value of H required to reduce the residual induction to zero after the material has been saturated (fully magnetized). |
| Hci – Intrinsic Coercive Force | Indicates a material's resistance to demagnetization. It is equal to the demagnetizing force which reduces the intrinsic induction, Bi, in the material to zero; measured in oersteds (or kA/m). As for coercivity, the maximum value of intrinsic coercivity is obtained after the material has been saturated (fully magnetized). |
| Induction (B) | Magnetic induction, B, is the magnetic field induced by an applied field,H. It is measured as the flux per unit area normal to the direction of the magnetic path. |
| Induction Curve, Normal | A graph depicting the relation between normal induction and magnetizing force. |
| Inductor | A coil that has significant self inductance, typically many turns of wire and with a permeable core. It is a device that stores and releases electromagnetic energy. See Inductance. |
| Intrinsic Coercivity | Same as Hci. Indicates a material's resistance to demagnetization. It is equal to the demagnetizing force which reduces the intrinsic induction, Bi, in the material to zero; measured in oersteds (or kA/m). As for coercivity, the maximum value of intrinsic coercivity is obtained after the material has been saturated (fully magnetized). |
| Intrinsic Demagnetization Curve | The hysteresis loop corresponding to B versus H where B is the magnetization resulting from only the magnetic material. For the Normal Curve, B corresponds to the sum of the externally applied field and the field of the magnetic material. |
| Isotropic | Having magnetic properties which are independent of the magnet orientation. Most magnetic materials are anisotropic as cast or powdered: each crystallite has a preferred direction of magnetic orientation. If the particles are not physically oriented during manufacture of the magnet, this results in a random arrangement of the particles and magnetic domains and produces isotropic magnet properties. Conversely, orienting the material during processing results in an anisotropic magnet. |
| 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/(4p) or 79.58 ampere-turns per meter; one kOe = 0.0796 kA/m. |
| Maximum Energy Product (BHmax) | The product of Bd and Hd which yield a maximum. See also, “BHmax”. |
| 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. | |
| Residual Flux | The flux that remains in a core when the applied MMF is returned to a value of zero. Changes in flux which occur with temperature change. They are spontaneously regained when the temperature is returned to its original point. |
| Reversible Temperature Coefficient | There are two values reported: Reversible Temperature Coefficients of Inductance (Br) and of Coercivity (Hci). The temperature range over which they have been measured and specified should be stated. Most materials exhibit a non-linear response with temperature. |
| Shielding | Thin-gauge sheet material used to protect sensitive devices from radiated EMI (electromagnetic interference). |
| Soft Magnetic Material | Shaped piece of ferromagnetic material that once having been magnetized is very easily demagnetized, i.e. requires a slight coercive force to remove the resultant magnetism. Generally accepted as having a coercivity of less than 300 oersteds (24 kA/m) though most soft materials used in inductors have coercivities of under 10 oersteds. |
| Tc – Curie Temperature | The transition temperature above which a material loses its (ferro)magnet properties. Most references state that the ferromagnetic material becomes paramagnetic (weakly magnetic). |
| Tmax – Maximum Service Temperature | The maximum temperature to which the magnet may be exposed with no significant long-range instability or structural changes. A proposed magnetic definition is that the hysteresis normal curve is substantially a straight line in the second quadrant up to the Tmax temperature and becomes curved above Tmax. |
| Temperature Coefficient | A factor which describes the reversible change in a magnetic property with a change in temperature. The magnetic property spontaneously returns when the temperature is cycled to its original point so long as a limit condition is not exceeded – see note below. It usually is expressed as the percentage change per unit of temperature over a specified temperature range.Note: above (or below) a critical temperature, dependent upon the material and its magnetic characteristics and magnetic circuit, an irreversible loss may take place which is recovered when the magnet is re-saturated.a See Reversible Temperature Coefficients |
| See Reversible Temperature Coefficients | |
| Temperature Stabilization | After manufacture, many types of hard and soft magnetic materials can be thermally cycled to make them less sensitive to subsequent temperature extremes. |
| Tesla | MKSA (SI) unit for magnetic flux density, defined by Faraday’s Law. ATesla represents a volt-second per square meter per turn. One Tesla equals 10,000 Gauss |