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Commonly used terms in the Electrical industry.
short circuit gain-bandwidth product
a measure of the frequency response capability of an electronic circuit. When applied to bipolar circuits, it is nominally the signal frequency at which the magnitude of the current
gain degrades to one.
short-circuit protection
the beneficial effect provided by an overcurrent device when it acts to interrupt short-circuit current.
shunt capacitor
a capacitor or group of capacitors which are placed across an electric power line to provide a voltage increase or to improve the power factor of the circuit. A switchable shunt may be disconnected from the circuit when conditions warrant, while a fixed shunt is permanently connected to the power line.
shunt peaking
use of a peaking coil in a parallel tuned circuit branch connecting the output load of one amplifier stage to the input load of the following stage, in order to compensate for high frequency loss due to the distributed capacitance of the two stages.
simplex
term used to describe a method of winding the armature of a commutated electric machine in which consecutive coils are placed in adjacent coil slots around the periphery of the rotor. In a lap winding, this produces two parallel electrical path between brushes for each pole pair. In a wave winding, a simplex arrangement produces two parallel electrical paths between brushes regardless of the number of poles. See also duplex, multiplex.
sine-squared pulse
pulse string made from a standard sinewave with an added DC component equal to one-half of the peak-topeak value of the sine wave. The pulse string is, therefore, always positive in value.
single phase to ground fault
See
single line to ground fault
single-phase inverter
an inverter with a single-phase AC voltage output. Half-bridge and full-bridge configurations are commonly used.
single-phase rectifier
a rectifier with a single-phase AC voltage input. See also half-wave rectifier and full-wave rectifier.
single-phasing
a condition that occurs when a three-phase motor has an open circuit occur in one of the three lines. The motor continues to operate with one line to line voltage as a single-phase motor, with an increase in noise, vibration, and current. Proper overload protection should detect the higher current and shut down the motor after some time delay.
single-pole reclosing
the practice of clearing a fault which appears on one phase of a three-phase electric power line by disconnecting and reclosing only that phase as opposed to opening and reclosing all three phase conductors.
single-pole double-throw (SPDT)
a switch that has a common port and two output ports. Among these two ports, only one selected port can be connected to the common port.
single-pole single-throw (SPST)
a switch that has a pair of input-output ports. By changing its status, the switch works as short or open circuit.
slip
in an induction motor, slip is defined as the ratio of the slip speed to the synchronous speed. The slip speed is the difference between the synchronous speed and the speed of the rotor.
See
synchronous speed
slip frequency
the frequency of the rotor induced currents in an induction machine. Denoted by fsl, the slip frequency is given by slip - stator frequency (fs) and is the prime frequency used in slip frequency control of induction machines.
slip power recovery control
a method of controlling the speed of a wound rotor induction machine by recovering the slip frequency power from the rotor to an AC power source or mechanical shaft through the converter connected to the rotor windings of the motor. Slip power recovery control reduces the losses that occur with rotor resistance control.
slip-ring contact
a rotating, brush-contacted ring electrode connected to one end of a coil in an AC generator.
slot pitch
the angular distance (normally in electrical degrees) between the axes of two slots.
spark gap
a pressurized high-current switch using a principle of electric field disruption to start the electron flow.
spectrometer
optical instrument that disperses broadband light into its component wavelengths, allowing the measurement of light intensity at each individual wavelength. Spectrometers may use prisms or gratings for wavelength dispersion and any of a variety of light detectors including photomultiplier tubes or charge-coupled devices.