PE Electrical Electronics key terms

A method of normalizing voltages, currents, impedances, and powers by dividing each quantity by a chosen base value, simplifying transformer and multi-voltage-level calculations by removing turns ratios from the equivalent circuit.

A technique that resolves an unbalanced three-phase set of phasors into three balanced sequence sets (positive, negative, and zero), allowing unbalanced faults and loads to be analyzed with per-phase equivalent networks.

The abnormally high current that flows when insulation fails or a conductor contacts ground or another phase, determined by source impedance and fault loop impedance and used to select protective device interrupting ratings.

The calculated distance from energized equipment at which incident thermal energy from an arcing fault equals the threshold for second-degree burns, establishing where personal protective equipment is required.

The ratio of real power to apparent power in an AC circuit, equal to the cosine of the angle between voltage and current for sinusoidal waveforms; low values increase current for a given delivered real power.

Adding shunt capacitors or synchronous condensers to supply reactive power locally, reducing the phase angle between voltage and current and lowering line current and losses for the same real power.

Power that oscillates between source and reactive elements without net energy transfer, measured in var, associated with magnetic fields in inductors and electric fields in capacitors.

The product of RMS voltage and RMS current in an AC circuit, measured in volt-amperes, representing the total capacity a source or conductor must supply regardless of phase angle.

A right-triangle representation in which resistance and reactance form the legs and impedance the hypotenuse, with the phase angle between them giving the voltage-current displacement.

A two-terminal linear network reduced to a single voltage source in series with a single impedance, used to simplify load and fault calculations without solving the full network each time.

A two-terminal linear network reduced to a single current source in parallel with a single admittance; it is the source transformation of the Thevenin equivalent and is convenient for nodal analysis.

A linear-circuit principle stating that the response to multiple independent sources equals the sum of responses computed with each source acting alone, with other voltage sources shorted and current sources opened.

A pair of graphs showing magnitude and phase of a transfer function versus logarithmic frequency, used to assess gain margin, phase margin, and stability of feedback systems.

The amount by which the open-loop phase exceeds minus 180 degrees at the frequency where open-loop gain is unity; a positive margin indicates a stable closed-loop system with adequate damping.

The ratio of a system output to its input in the Laplace or frequency domain under zero initial conditions, capturing poles and zeros that determine transient and steady-state behavior.

A plot of the closed-loop pole locations as a gain parameter varies from zero to infinity, used to judge how gain changes affect stability and transient response.

A feedback controller combining proportional, integral, and derivative action on the error signal; the integral term removes steady-state offset while derivative action adds damping.

A stability test that counts encirclements of the minus-one point by the open-loop frequency response to determine closed-loop pole locations for a feedback system.

A static device transferring energy between circuits by electromagnetic induction, with primary and secondary windings rated for voltage, apparent power, and temperature rise; used to step voltage up or down.

Power dissipated as circulating currents induced in a magnetic core by alternating flux, minimized by laminating or using ferrite cores and increasing roughly with the square of frequency and flux density.

Energy lost per magnetization cycle as the core material is driven around its B-H loop, proportional to frequency and loop area and reduced by choosing soft magnetic materials.

The tendency of alternating current to concentrate near the surface of a conductor as frequency rises, raising effective resistance and reducing usable cross section.

The redistribution of current within a conductor caused by magnetic fields from nearby conductors, raising AC resistance and complicating loss estimates in windings and busbars.

An AC machine in which stator currents induce rotor currents that produce torque; rotor speed is below synchronous speed by the slip, and no external rotor connection is needed.

The rotational speed of the rotating magnetic field, equal to 120 times frequency divided by the number of poles, which sets the reference speed for induction and synchronous machines.

The fractional difference between synchronous speed and actual rotor speed of an induction machine, positive in motoring, negative in generating, and used to compute rotor frequency and torque.

A machine whose rotor turns at exactly synchronous speed and whose field excitation sets terminal voltage and reactive power, used for most utility-scale generation.

A plot of magnetic flux density versus magnetizing field strength for a material, whose slope gives permeability and whose loop area gives hysteresis loss per cycle.

The fraction of a switching period during which a switch or signal is in its active state, which sets the ideal voltage conversion ratio in switching converters.

A switching DC-DC converter that steps voltage down, using an inductor, switch, and diode or synchronous rectifier to average the input voltage according to duty cycle.

A technique that varies the on-time of a switching signal at fixed frequency to control average voltage or power, widely used in motor drives, converters, and inverters.

The ratio of the RMS of all harmonic components above the fundamental to the RMS of the fundamental, quantifying waveform distortion in converters, drives, and power systems.

A set of conductive elements in contact with earth that establishes a reference potential and provides a path for fault and lightning currents, sized per installation code requirements.

A conductor ensuring electrical continuity between metal parts that must be at the same potential, preventing dangerous voltage differences during faults.

The maximum current a conductor can carry continuously under stated conditions without exceeding its temperature rating, adjusted for ambient temperature and conductor bundling.

The reduction in voltage along a conductor caused by its impedance and load current, limited by code and design rules to keep equipment terminal voltage within tolerance.

A differential amplifier with high input impedance and precisely set gain, typically built from three op-amps, used to amplify small signals from sensors and bridges in the presence of common-mode noise.

The ratio of differential gain to common-mode gain in a differential amplifier, expressing how well unwanted signals present on both inputs are suppressed.

A high-gain differential voltage amplifier treated as an ideal building block with virtual-short behavior in negative feedback, used for amplification, filtering, and signal conditioning.