Electrical Engineers and Master Electricians (EEAME) Portal
Home
Dictionary
Tutorials
General
Specifications
Forums
Disclaimer
Devices
Dictionary of Electrical Engineering
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
ALL
Commonly used terms in the Electrical industry.
DC offset current
the exponentially decaying current component that flows immediately following a fault inception. DC offset is the result of circuit inductance, and is a function of the point in the voltage wave where the fault begins. The offset for a given fault can range from no offset to fully offset (where the instantaneous current peak equals the full peak-peak value of the AC current).
direct current machine
a DC machine is an electromechanical dynamo that either converts direct current electrical power into mechanical power (DC motor), or converts mechanical power into direct current electrical power (DC generator). Some DC machines are designed to perform either of these functions, depending on the energy source to the dynamo.
direct current motor
a rotation machine energized by DC electrical energy and used to convert electrical energy to mechanical energy.
directional overcurrent relay
an over-current relay that operates only for overcurrents flowing in the tripping direction. Direction sensing is typically done with respect to a voltage or current signal, which is not affected by fault location.
dropout current
the current at which a magnetically-operated device will revert to its de-energized position.
eddy current
a circulating current in magnetic materials that is produced as a result of time-varying flux passing through a metallic magnetic material.
eddy current brake
a braking device in which energy is dissipated as heat by generating eddy currents.
eddy current drive
a magnetic drive coupled by eddy currents induced in an electrically conducting member by a rotating permanent magnet, resulting in a torque that is linearly proportional to the slip speed.
eddy current loss
the energy wasted in sustaining undesirable eddy currents in an electrical conductor.
electric current density
a source vector in electromagnetics that quantifies the amount of electric charge crossing some cross-sectional area per unit time. The direction of the electric current density is in the direction of electric charge motion. SI units are amperes per square meter.
equivalent current
a theoretical current used to obtain the scattered field from a surface or discontinuity. The equivalent current is formulated to represent the actual physical currents so as to result in an equivalent scattered field.
exciting current
the current drawn by a transformer primary with its secondary open circuited. It is the vector sum of the core loss current Ic and the magnetizing branch current Im . The exciting current I
e
is also the current measured in the open circuit test on a transformer. The exciting current is calculated as the ratio of the primary induced EMF and the impedance of the tank circuit. On load, it is equal to the difference between the primary and reflected secondary currents of the transformer.
field current control
a method of controlling the speed of a DC motor by varying the field resistance, thus producing a change in the field current.
ground current
the current that flows in a power system in a loop involving earth and (in some usages) other paths apart from the three phases.
inrush current
the transient current drawn by an electrical apparatus when it is suddenly connected to a power source. The inrush current may be larger in magnitude than the steady-state full-load current. The transient response is short in time and the electrical equipment generally supports the inrush current, provided it does not happen frequently. For a single transient, the thermal limit of the equipment is not reached, but if it is switched on and switched off several times within a short period, the temperature can rise very quickly. In case of transformers, the inrush current is not sinusoidal even if the voltage is due to the hysteresis of the ferromagnetic core.
instantaneous overcurrent relay
an overcurrent relay that operates with no intentional delay following sensing of a power frequency overcurrent, i.e., a current above its set point.
Kirchoff's current law (KCL)
a fundamental law of electricity that states that the sum of the currents entering and exiting a circuit node must be equal to 0.
line-current harmonic
See
electromagnetic interference filter
locked-rotor current
the current drawn by an induction motor when the shaft is not moving and rated voltage is applied. The starting current is essentially equal to the locked rotor current and may be as much as eight times the rated current of the machine.
magnetic current density
a fictitious source vector in electromagnetics that quantifies the amount of magnetic charge (also fictitious) crossing some cross-sectional area per unit time. The magnetic current density is often introduced in problems where duality and equivalence concepts are employed. The direction of the magnetic current density is in the direction of magnetic charge motion. SI units are volts per square meter.