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Electrical Engineering Terms I

I/O Module

Field replaceable modules that accept or send signals from field devices and condition the signal for the CPU.

IGBT

Insulated Gate Bipolar Junction Transistor – A semiconductor device that provides the base technology for the modern drive.

Imperial Units

These are the measurement units used in the United States. Typical units are feet, inches, pounds, and horsepower.

Inductive Choke. The name was given to an inductor (a coil of wire) when used to reduce variations in a DC voltage source. These types of inductors are used in DC power supplies to help reduce any line frequency fluctuations on the DC output. In AC circuits, these types of inductors are normally used to add inductive reactance and change the impedance of the circuit.

Insulator / Insulated. A conductive surface separated from other conducting surfaces by a dielectric material or airspace, which offers a high resistance to the passage of current or to a disruptive discharge (electrical arc) through the dielectric or airspace.

Inverse-Time. Inverse-time means the elapsed time or speed of response to overcurrent by an overcurrent protection device will be inversely proportional to the magnitude of the overcurrent. In other words, the higher the magnitude of overcurrent, the faster the overcurrent protection device will open, and by the same token, the lower the magnitude of the magnitude of overcurrent, the slower the overcurrent protection device will open.

Ionized / Ionic. A heavy concentration of electrically charged atoms that either has a surplus of free or valence (outer-orbit) electrons (negative charge), or a depletion of free electrons (positive charge).

Impedance (ZVirtual Resistance). Normally abbreviated to the acronym Z, the total opposition to current flow in an AC circuit at a given frequency, impedance is a combination (vector sum) of resistance and reactance [either capacitive reactance (XC) or inductive reactance (XL), or their difference when both are present in a given circuit] that is measured in ohms. Because both inductive and capacitive reactances are sensitive to changes in the source frequency, AC circuit impedance is also sensitive to changes in the source frequency.

Induction. This type of electrical phenomenon is the property of an electrical circuit where a length of conductor, a concentrated magnetic (or electromagnetic) field and relative motion between the two, induces a voltage along the length of the conductor. Induced current will flow only if a closed circuit is present.

Intermittent Duty. If an electric motor is nameplate-rated with this type of duty cycle, it is rated to operate for alternate intervals of (1) load and no load; or (2) load and rest; or (3) load, no load, and rest.

Induction. The property of current flow in an electrical circuit where a length of conductor, a concentrated magnetic (or electromagnetic) field and relative motion between the two induces a voltage along the length of a second conductor in close proximity of the first.  Induced current will flow in the second conductor only if a closed circuit is present.

Iron Core Losses. The expended electrical energy of the excitation current in a transformer ― normally dissipated as heat (I2R losses).

Isolation Transformer. Also referred to as a conventional transformer, this transformer is constructed with the primary and secondary circuits isolated (insulated) from each other, such that there is no electrical or mechanical metallic connection between the two circuits.

About Ahmed Faizan

Mr. Ahmed Faizan Sheikh, M.Sc. (USA), Research Fellow (USA), a member of IEEE & CIGRE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from Kansas State University, USA.

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Electrical Engineering Terms D

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