Electrical Engineers and Master Electricians (EEAME) Portal

Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

an electromechanical system that converts alternating current electrical power into mechanical power.

an induction motor whose rotor is occupied by copper or aluminum bars, known as rotor bars, instead of windings. Also commonly referred to as a squirrel-cage induction motor.

capacitor-start induction motor (CSIM)

a single-phase induction motor with a capacitor in series with its auxiliary winding, producing nearly a 90. phase difference between the main winding and the auxiliary winding currents at starting. This results in a high starting torque, so this motor is used for hard-to-start loads. The auxiliary winding and capacitor are removed from the circuit by a centrifugal switch as the machine approaches operating speed.

DC motor

a motor that operates from a DC power supply. Most DC motors have a field winding on the stator of the machine that creates a DC magnetic field in the airgap. The armature winding is located on the rotor of the machine and the DC supply is inverted by the commutator and brushes to provide an alternating current in the armature windings.

DC motor drive

a converter designed to control the speed of DC motors. Controlled rectifiers are generally used and provide a variable DC voltage from a fixed AC voltage. Alternatively, a chopper, or DC-DC converter, can be employed to provide a variable DC voltage from a fixed DC voltage.

definite time DC motor acceleration

when DC motors accelerate during their starting sequence, starting resistors are removed from the armature circuit in steps. In definite time DC motor acceleration (also referred to as open loop DC motor acceleration), the starting resistors are removed in definite time increments, whether the motor is actually accelerating or not.

definite-purpose motor

any motor design, listed and offered in standard ratings with standard operating characteristics, with special mechanical features for use under service conditions other than usual or for use on a particular type of application.

direct current motor

a rotation machine energized by DC electrical energy and used to convert electrical energy to mechanical energy.

electronic motor starter

starter in which solid state devices provide reduced voltage to the motor for starting, thus limiting the starting current.

general-purpose motor

term often used to describe National Electrical Manufacturers Association (NEMA) class B, and less often class B, induction motors. Generalpurpose motors are those typically used when relatively low starting currents, low slip, good speed regulation, moderate starting torque, and high efficiency are the predominant concerns.

hybrid stepper motor

a stepper motor that combines the rotor design characteristics of variable-reluctance and permanent magnet stepper motors. Hybrid stepper motor rotors consist of an axially magnetized cylindrical permanent magnet capped on each pole by toothed, soft iron caps. Teeth on the caps are displaced with respect to each other to provide stepping control. Hybrid stepper motors combine the higher torque capability of permanent magnet motors with the higher step resolution of variable-reluctance motors.

hysteresis motor

any of a variety of single-phase AC motors that use the hysteresis properties of hard magnetic materials to develop torque. Stator windings of a hysteresis motor can be of any design that produces a rotating flux within the machine. Motion of the rotating flux over the rotor magnetizes the hard magnetic material on the rotor; however, the hysteresis characteristics of the material cause the alignment of magnet flux to lag the rotating stator flux. This misalignment produces rotor torque. Because of the nature of the torque production, hysteresis motors operate at synchronous speed and have a constant torque characteristic, which permits them to synchronize any load that they
can accelerate.

induction motor

See induction machine

integral horsepower motor

a motor built in a frame as large as or larger than that of a motor of open construction having a continuous rating of one horsepower at 1700-1800 rpm.

magnetic motor starter

motor starter that uses electromechanical devices such as contactors and relays.

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.