Electrical Engineers and Master Electricians (EEAME) Portal

Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

a unit of area used to specify the cross-sectional area of a wire, equal to 1000 circular mils.

a fully-insulated three-phase aerial cable in which three individual insulated conductors are carried on insulated looms hung upon a bare messenger wire. Such cable is used frequently in distribution work.

messenger wire

a grounded wire which is used to structurally support an aerial cable.

metadyne

a DC machine with more than two brush sets per pair of poles. The additional brushes are located in the direct axis for the armature MMF to provide most of the excitation for higher gains.

metal halide

molecule formed by the reaction of metals and halogen atoms.

metal-insulator-metal (MIM)

capacitor a capacitor, which has a thin insulator layer between two metal electrodes. Generally, this capacitor is fabricated in semiconductor process, and this insulator layer provides high capacitance. Two extreme behaviors of a capacitor are that it will act as an open circuit to low frequencies or DC (zero frequency), and as a short frequency at a sufficiently high frequency (how high is determined by the capacitor value).
See thin film capacitor

MHz

egahertz, or millions of operations per second.

molded case circuit breaker

a low voltage air circuit breaker that includes thermal and/or magnetic overcurrent sensing which directly trips the breaker. The molded case circuit breaker is nearly always manually closed, opened, and reset.

momentary interruption

a loss of voltage of less than 0.1 pu for a time period of 0.5 cycles to 3 seconds.
momentary monitoring the duration at supply frequency from 30 cycles to 3 seconds.

momentary overvoltage

an increase in voltage above the system's specified upper limit for more than a few seconds. Generally a rather loosely-defined term.

motor

an electromechanical device that converts electrical energy from a DC or an AC source into mechanical energy, usually in the form of rotary motion.

motor circuit

the three components of an electrical circuit are source, load, and interconnecting circuit conductors. A motor circuit is an electrical circuit designed to deliver power to a motor. It includes the over-current protective devices, controller, disconnect switch, circuit conductors, and the motor itself.

motor circuit protector (MCP)

a listed combination motor controller containing an adjustable instantaneous-trip circuit breaker and coordinated motor overload protection. MCPs can provide short-circuit and bolted ground-fault protection via the circuit breaker magnetic element, overload protection via the overload device, motor control, and disconnecting means all in one assembly.

motor control center (MCC)

an enclosure with one or more sections containing motor control units that have a common power bus.

motor control circuit

a circuit containing devices such as the start/stop switches, mainline coil, main-line sealing contacts, overload contacts, timers and timer contacts, limit switches, antiplugging devices, and anything else used to control devices in the motor circuit.

motor current signature

analysis the use of the currents of an electric machine to provide diagnostic or other information on the health of the machine, coupling, or load.

motor operated switch

a switch operated by a motor that is capable of being controlled from a remote location.

Motor service factor (SF)

The percentage multiplier that a motor can handle for short periods of time when operating within its normal voltage and frequency tolerance. In other words, it is a fudge factor that give extra horsepower when it's occasionally needed.

motor starter

an electric controller, either manual or automatic, for accelerating a motor from rest to normal speed and for stopping the motor.

motor-generator set

a set consisting of a motor mechanically coupled to and driving one or more generators. The set used to be employed for AC-to-DC or DC-to-AC power conversion or voltage level or frequency conversion. Solid-state conversion units are replacing motor-generator sets in most applications.