Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

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.
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 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.
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.
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.
brownout
an intentional lowering of utility voltage to reduce loading on the system.
brush tension
the force required on the brushes of a rotating machine to insure proper contact between the brush and the commutator or slipring. Proper brush tension is usually provided by springs, and is specified in the manufacturer's technical manual of the machine.
brushless DC motor

See electronically commutated machine
brushless exciter

See rotating-rectifier exciter
brushless rotary flux compressor
a rotating machine designed to deliver pulsed output (1 MJ in 100 µs). The stator coils are excited by an external capacitor bank. The rotor is a salient structure that compresses the flux resulting in amplification of the electric pulse, by converting the rotating kinetic energy of the rotor to electrical energy.
bulb generator
a free-standing generator contained in a streamlined, waterproof bulb-shaped enclosure and driven by a waterwheel resembling a ship's propeller on a shaft which extends from one end of the enclosure. They are used in tidal power installations.
bulk substation
a substation located on a high-voltage transmission line which supplies bulk power to a non-generating utility.
bus admittance matrix

See Y-bus
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