Electrical Definitions


 Copyright - Durand & Associates  

Electrical Definitions

Letter - M

Maximum Operating Voltage

The maximum voltage the unit can sustain without damage or failure.



A unit of electrical resistance equal to one million ohms.



A test instrument for measuring the insulation resistance of conductors and other electrical equipment; specifically, a mega-ohm (million ohms) meter; this is a registered trademark of the James Biddle Co.


Metal-Enclosed Power Switchgear

A switchgear assembly completely enclosed on all sides and top with sheet metal (except for ventilating openings and inspection windows) containing primary power circuit switching, interrupting devices, or both, with buses and connections. The assembly may include control and auxiliary devices. Access to the interior of the enclosure is provided by doors, removable covers, or both.



A machine which converts electrical power into mechanical power.


Motor Control Center

An assembly of one or more enclosed sections having a common power bus and principally containing motor control units.


Motor-Generator Set

A conversion device consisting of one or more motors mechanically coupled to one or more generators.


Motor Induction Type

An alternating current motor, either single phase or polyphase, comprising independent primary and secondary windings, in which the secondary receives power from the primary by electromagnetic induction.


Motor Synchronous Type

An alternating current motor which operates at the speed of rotation of the magnetic flux.


Multioutlet Assembly

A type of surface, flush, or freestanding raceway designed to hold conductors and receptacles, assembled in the field or at the factory.