Electrical Engineers and Master Electricians (EEAME) Portal

Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

line to line fault

a fault on a three phase power line in which two conductors have become connected.

line-connected reactor

See shunt reactor

line-current harmonic

See electromagnetic interference filter

line-to-line voltage

a voltage measurement of a three phase line made between any two conductors.

lineman

utility employee working on primary facilities, distribution class equipment, as opposed to customer service level facilities.

linkage flux

also called magnetizing or mutual flux. In a magnetically coupled circuit such as a transformer, the linkage flux is the flux that links all the windings. For example, in a transformer the magnetic flux produced by the primary winding which is coupled to the secondary winding.

load center

the geographic point within a load area, used in system calculations, at which the entire load could be concentrated without affecting the performance of the power system.

load flow study

See power flow study

load frequency control

the purpose of load frequency control is to maintain the power system frequency at its nominal value while maintaining the correct outputs on individual generators to satisfy the loading on the system. As the load varies, the inputs to the generator prime movers must be controlled to keep the generation in balance with the loads.

load line

with a slope, also known as the permeance coefficient, determined solely by the geometry of the magnetic circuit, this line intersects with the normal demagnetization curve to indicate a magnet's operating point.

load mismatch

the load impedance does not match the device output impedance, resulting in power reflection. A perfect match occurs when the real parts of the load and device output impedance are equal and the reactive parts cancel or resonate, resulting in maximum power transfer. The magnitude of the load mismatch is usually expressed in terms VSWR, reflection coefficient or return loss.

load tap changer (LTC)

a tapped transformer winding combined with mechanically or electronically switched taps that can be changed under load conditions. The load tap changer is used to automatically regulate the output of a transformer secondary as load and source conditions vary.

load torque

the resisting torque applied at the motor shaft by the mechanical load that counterbalances the shaft torque generated by the motor and available at the shaft.

load-break device

any switch which can be opened while the circuit is loaded

load-commutated inverter (LCI)

an inverter in which the commutating voltages are supplied by the load circuit.

load-pull

the systematic variance of the magnitude and phase of the load termination of a device under test.

loaded Q

dimensionless ratio of the average over any period of time (T = 1/frequency) of the ratio of the maximum energy stored (Umax) to the power absorbed or dissipated (P_absorbed = P_in - P_out) in a passive component or circuit, including external loading effects, expressed as a dimensionless ratio. For most applications, the higher the Q, the better the part.

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.

locked-rotor torque

the torque produced in an induction motor when the rotor is locked and rated AC voltage is applied to the stator.

lockout

the condition following fault clearing when the circuit will not attempt a reclose. Transformers, generators, and buses typically trip once and lockout immediately. Transmission lines and distribution lines will generally attempt one or more recloses, and will lockout if the fault remains following the last reclose in the sequence.