Gowanda Electronics — Technical Library

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Glossary of Terms

AC Flux Density (Gauss): Number of flux lines per unit of cross-sectional area generated by an alternating magnetic field.
Copper Loss (Watts): The power loss (PR) or heat generated by current (l) flowing in a winding with resistance (R).
Core: Magnetic material placed within and around a coil to provide a path of lower reluctance for magnetic flux.
Core Loss: The power loss or heat generated by a magnetic material subjected to an alternating magnetic field.
Current Rating (ldc): The maximum recommended DC current for the inductor. Expressed in milliamps (mA) or amps (A) maximum.
DCR: The direct current (DC) resistance offered by an inductor due to the resistance of the magnet wire used to wind. Expressed in ohms or milliohms maximum. This is an undesirable characteristic, which is a by-product of the wire or conductive material used. The lower the DCR, the more current an inductor will handle.
Flux: Product of the average component of magnetic induction perpendicular to any given surface in a magnetic field by the area of that surface, expressed in webers.
Flyback Transformer: Used in a flyback power supply. Also called horizontal output transformer.
Incremental Current (dl): The amount of DC current which causes the inductor to lose a defined percentage of its inductance (starting to saturate). Of primary concern when lower than rated current.
Inductance: The property of a circuit element that opposes changes in Alternating Current (AC). Expressed in millihenries (mH), microhenries (µH), or nanohenries (nH) and should carry a tolerance (i.e. ± 5% or ±10%). As a rule, the inductance remains relatively constant past its Test Frequency.
Inductors: Electrical components that oppose any change of AC current by means of storing energy in a magnetic field.
Iron-Core Coil/Transformer: Coil/transformer wound around an iron core to increase its inductance. At radio frequencies the core consists of powdered iron mixed in a binder which insulates the particles from each other.
Isolation Transformer: Transformer with a one-to-one turns ratio, connected between the a.c. power input to a piece of equipment and the a.c. line, to minimize shock hazard.
Load Loss: The power loss (I2R) or heat generated by current (I) flowing in a winding with resistance (R).
Maximum Power Dissipation: An inductor's ability to handle the heat generated by operating at maximum current at an ambient temperature, expressed in Watts (W) or milliwatts (mW). This is a function of the body area of the inductor and core material used.
No Load Loss (Core Losses): These losses are caused by the magnetizing of the core and are always present. The way they are measured is by running full voltage with no load on the transformer.
Operating Temperature Range: Specifies the temperature extremes at which the inductor will operate safely. At the maximum temperature specified, allowance must be made for the "Temperature Rise" created by heating effects of using the inductor at its maximum current rating. Gowanda uses 90 degrees Celsius as ambient temperature for rating current; thus 125 degrees operating minus 90 degrees ambient, allows 35 degrees for temperature rise.
Percent Saturation: This is equal to 100% minus Percent initial Permeability, ie: 20% saturation = 80% of initial permeability.
Permeability (u): By definition u = B/H, where B is the flux density in gauss and H is the magnetizing force in oersteds.
Power Transformer: Magnetic-core transformer for operation at 60 hertz, with nearly zero source impedance, to transfer power from line voltage to some required voltage.
Primary Winding: The winding connected to the source of energy.
Q: Quality Factor of an inductor relates to the amount of energy lost while an AC current is passing through it. It is expressed as a minimum value (i.e. 50 minimum). In most applications the higher the value of Q, the better the inductor will perform.
SRF: The inductor's self resonant frequency; the frequency at which the inductor looks electrically capacitive, rather than inductive. Expressed in megahertz (MHz) minimum. The higher the value, the greater the range of frequency use.
Secondary Winding: The winding is the coil where energy is induced from the primary.
Shielded: Shielded inductors have internal iron or ferrite around the entire winding to prevent unwanted signals from escaping and interfering with the other components in the immediate area.
Turn Ratio: The ratio of the primary voltage (or turns) to the secondary voltage (or turns).
Step Up Transformer: When the secondary is at a higher voltage than the primary.
Step Down Transformer: When the secondary has a lower voltage than the primary.
Saturation (see Percent Saturation): Maximum density of magnetic flux that can be present in a magnetic material.
Temperature Coefficient of Inductance: (Tc of L) is the value of inductance change as a function of temperature exposure, normally expressed in parts per million per degrees Celsius. This is a calculation comparing inductance at a reference temperature (25°C, room ambient) to the extremes and other temperatures within operating range. Can be called Percent Delta L or Temperature Stability; the lower the change the better for most applications.
Test Frequency: The industry/military standard for testing a range of inductances. It is not intended as the application frequency. Expressed in megahertz (MHz) or kilohertz (KHz).