Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

copper loss
electric loss due to the resistance in conductors, windings, brush contacts or joints, in electric machinery or circuits. Also referred to as I2R, the losses are manifested as heat.
core loss
loss in the ferromagnetic material comprising the core of an electric machine or transformer, composed of the sum of hysteresis losses and eddy current losses. These magnetic losses are caused by time varying fluxes in a ferromagnetic structure.
Hysteresis losses are caused by friction in molecules as the dipoles in a structure change direction of alignment in response to an applied alternating voltage, while eddy current losses are resistive losses .I 2R/, due to circulating currents in the core.



See magnetic core memory
corona loss
the electric power lost in high voltage lines due to the radiation of energy by corona discharge.

See corona
eddy current loss
the energy wasted in sustaining undesirable eddy currents in an electrical conductor.
field loss protection
a fault-tolerant scheme used in electric motors. Some DC motor control circuits provide field loss protection in the event the motor loses its shunt field. Under a loss of field, DC motors may overspeed causing equipment damage and/or personal injury. In a motor controller that has field loss protection, a sensor determines when the shunt field has lost current flow, then secures the motor before an overspeed condition occurs.
fixed losses
that component of the copper losses in DC shunt, short-shunt, and long-shunt machines' field circuit, that does not vary with change in the load current. With a fixed field power supply, it is an accepted industry agreement to not consider the losses in the field circuit rheostat in computing the efficiency and hence consider the field losses
as fixed losses.
high-loss resonator
a resonator having a high value of loss (usually diffraction loss) per round trip; unstable resonator.
hysteresis loss
the energy loss due to hysteresis in a magnetic material subjected to a varying magnetic field.
insertion loss
(1) worst-case loss of the device across the stated frequency range. The loss due to the insertion of the unit in series with a signal path.

(2) transmission loss of an RF or microwave component or system, typically measured in decibels.
light loss factor (LLF)
the ratio of the illumination when it reaches its lowest level at the task just before corrective action is taken, to the initial level if none of the contributing loss factors were considered.
loss
(1) decrease of intensity of an electromagnetic wave due to any of several physical mechanisms. See also attenuation.
(2) a term for electric power which does not register on the consumer's electric meter, e.g., through ohmic losses in transmission lines, iron losses in transformers, or theft.
loss coefficient
a factor used in economic dispatch calculations that relates power line losses to the power output of generating plants.
loss factor
the product of the dielectric constant and the power factor.
loss of service
the complete loss of electric power exclusive of sags, swells, and impulses.
loss tangent

See dissipation factor
loss-of-field relay
a protection relay used to trip a synchronous generator when the excitation system is lost. Loss of excitation causes the generator to run as an induction generator drawing reactive power from the system. This can cause severe system voltage reductions and damage to stator due to excessive heating.
magnetic loss
losses in magnetic flux in a magnetic circuit, primarily due to magnetic leakage and fringing.
See core loss
ohmic loss
a term used to describe the power dissipated due to the finite conductivity of the metallic structure of an antenna, waveguide, transmission line, etc.
rotational loss
one of several losses in a rotating electric machine that are primarily due to the rotation of the armature and include the friction and windage losses. Also called mechanical loss. They can be determined by running the machine as a motor at its rated speed at no load, assuming the armature resistance is negligible.
rotor power loss
represents the portion of the power transferred across the air gap to the rotor of an induction motor that is lost either through ohmic heating of the rotor windings or due to friction and windage losses in the rotor. The mechanical power available at the motor shaft is the difference between rotor power input and rotor power losses.
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