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.
ambient field
the background magnetic field level existing in the environment, without contribution from specific magnetic field sources.
current density vector field
the field (commonly denoted J ) that is related to the electric field intensity vector field by the conductivity of the medium that the fields are located in. One of the quantities found on the right side of Ampere's Law. The units are (amperes/square meter).
electric field
in a region of space, if a test charge q experiences a force F then the region is said to be characterized by an electric field of intensity E given by
E = F / q
electric field intensity
a force field that is a measure of the magnitude and direction of the force imparted upon a discrete charge normalized to the discrete charge's value. Depends on material characteristics. The units are volts per meter.
field
(1) the member of an electrical machine that provides the main magnetic flux, which then interacts with the armature causing the desired machine operation (i.e., motor or generator).
(2) a description of how a physical quantity varies as a function of position and possibly time. See also electric field, finite field.
field circuit
a set of windings that produces a magnetic field so that the electromagnetics induction can take place in electric machines.
field controlled thyristor (FCT)
a thyristor controlled by change in the magnitude of the field current.
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.
field discharge resistor
a resistor used to dissipate the energy stored in the inductance of a field winding. It may be a standard power resistor that is connected across the winding just prior to opening the supply switch, or a permanent non-linear resistive device that has high resistance at normal voltage but low resistance when voltage rises at switching.
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.
field propagator
the analytical description of how electromagnetic fields are related to the sources that cause them. Common field propagators in electromagnetics are the defining Maxwell equations that lead to differential equation models, Green's functions that produce integral equation models, optical propagators that lead to optics models,
and multipole expansions that lead to modal models.
field reversing
a method of achieving a reversal of rotation of a DC motor by reserving the field flux.
field strength
in general terms the magnitude of the electric field vector (in volts per meter) or the magnitude of the magnetic field vector (in ampere-turns per meter). As used in the field of EMC/EMI, the term is applied only to measurements made in the far field and is abbreviated as FS. For measurements made in the near field, the term
electric field strength (EFS) or magnetic field strength (MFS) is used, according to whether the resultant electric or magnetic field, respectively, is measured.
field weakening
a method of achieving speed increase in DC motors by reducing the field flux (increasing field circuit resistance).
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 field
magnetic force field where lines of magnetism exist.
magnetic field intensity
a force field that is a measure of the magnitude and direction of the force imparted upon an elemental current normalized to the elemental current's value. Depends on material characteristics. The units are amperes per meter.
revolving field
the magnetic field created by flow of a set of balanced three-phase currents through three symmetrically displaced windings. The created field revolves in the air-gap of the machine at an angular velocity corresponding to the synchronous speed of the machine. The revolving field theory is the basis of functioning of synchronous and induction machines.
self-demagnetizing field
a field inside of a permanent magnet that is opposed to its own magnetization, which is due to internal coupling of its poles following the introduction of an air gap in the magnetic circuit.
shunt field
a field winding of a DC machine consisting of many turns of fine wire, connected in parallel with the armature circuit. It may be connected to the same source as the armature or a separate source.