Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

an insulating rubber mat which is fitted temporarily over energized conductors to protect nearby workers.
blocked-rotor current

See locked-rotor current
blocked-rotor test
an induction motor test conducted with the shaft held so it cannot rotate. Typically about 25% of rated voltage is applied, often at reduced frequency and the current is measured. The results are used to determine the winding impedances referred to the stator.
boiling water reactor
a nuclear reactor from which heat is transferred in the form of high-pressure steam.
bolted fault
a bolted fault is a short circuit fault with no fault resistance. Bolted faults deliver the highest possible fault current for a given location and system configuration, and are used in selecting equipment withstand and interrupting ratings and in the setting of protective relays.
a curve that separates two sets of points.
boundary bus
one of a set of buses which define the boundary between the portion of a power system to be analyzed and the rest of the system. Boundary buses are connected to both the internal and external systems.
operating condition in an electric motor in which the torque developed between the stator and rotor coils opposes the direction of rotation of the rotor. Typical braking methods in DC machines include "plugging" in which the polarity of either the field or the armature coil, but not both, is reversed while the rotor is turning, "dynamic braking" in which generator action in the armature is used to dissipate rotor energy through a braking resistor, and "regenerative braking" in which generator action in the rotor is used to dissipate rotor energy by returning electric power to the power source as the rotor slows. Typical braking methods in AC machines include switching of the phase sequence of the supply voltage, dynamic braking through the armature coils, and varying the frequency of the AC supply voltage.
See phase sequence
braking resistor
resistive elements which can be switched into the electrical system to create additional load in the event of a transient disturbance, thus limiting the generator rotor acceleration such that the system can more readily return to synchronism.
branch circuit
the three components of an electrical circuit are source, load, and interconnecting circuit conductors. A branch circuit is an electrical circuit designed to deliver power to the lowest-order load(s) served on a facility. It includes the overcurrent device, circuit conductors, and the load itself.
branch current
the current in a branch of a circuit.
branch line coupler
coupler comprised of four transmission lines, each of 90. electrical length, arranged in a cascaded configuration with the end of the last transmission line section connected to the beginning of the first transmission line to form a closed path. The input, coupled, direct, and isolated ports are located at the connection point of one transmission line with the next one.
branch voltage
the voltage across a branch of a circuit.
breakaway torque
minimum torque needed to begin rotating a stationary load. Breakaway torque represents the absolute
minimum starting torque specification for a motor used to drive the load.
as applied to insulation (including air), the failure of an insulator or insulating region to prevent conduction, typically because of high voltage.
breakdown strength
voltage gradient at which the molecules of medium break down to allow passage of damaging levels of electric current.
breakdown torque
maximum torque that can be developed by a motor operating at rated voltage and frequency without experiencing a significant and abrupt change in speed. Sometimes also called the stall torque or pull-out torque.
a service or system requiring transmission channels capable of supporting bit rates greater than 2 Mbit/s.
broadband integrated services digital network (B-ISDN)
a generic term that generally refers to the future network infrastructure that will provide ubiquitous availability of integrated voice, data, imagery, and video services.
Brown book

See IEEE Color Books