Electrical Machines 2 - Comprehensive Motor Reviewer

Flashcard set covering vocabulary, concepts, connections, formulas, and operating characteristics of DC and AC electrical machines based on the board reviewer notes.

DC Motor

A continuous energy-conversion device that converts direct current electrical input energy into mechanical output energy.

Separately Excited DC Motor

A DC motor whose field winding is supplied by an independent excitation power supply separate from the armature circuit, allowing for precise speed control.

Series-Wound DC Motor

A DC motor having its field winding connected in series with the armature, producing high starting torque suitable for heavy starting loads.

Shunt-Wound DC Motor

A self-excited DC motor whose field winding is connected in parallel with the armature, providing nearly constant speed operation across varying loads.

Back EMF

The counter-electromotive force generated in a DC motor armature that is directly proportional to field flux and rotational speed $N_r$; it increases as motor speed increases.

Compound DC Motor

A DC motor equipped with both series-field and shunt-field windings to combine the high-torque characteristics of a series motor with the speed regulation of a shunt motor.

Long-Shunt Compound DC Motor

A compound DC motor arrangement in which the shunt field winding is connected in parallel across the combined series combination of the armature and series field.

Short-Shunt Compound DC Motor

A compound DC motor arrangement in which the shunt field winding is connected in parallel directly across the armature terminals only.

Armature Core

The slotted rotating core component of a DC motor in which the armature winding is physically embedded.

AC Motor

An electrical machine that converts alternating current electrical energy into mechanical output energy, typically operated by a rotating magnetic field.

Rotating Magnetic Field Principle

The operating principle of AC motors wherein alternating currents in stator windings create a moving magnetic field that drives the rotor.

Induction Motor (Asynchronous Motor)

An AC motor in which rotor current is induced by the stator's rotating magnetic field without direct external electrical connections; characterized by simple, rugged construction and low maintenance.

Synchronous Motor

An AC motor whose rotor turns at exactly synchronous speed $N_s$ during steady-state operation, requiring rotor excitation via permanent magnets or an external DC supply.

Shaded-Pole Motor

A self-starting, single-phase induction motor that uses a copper shading ring around part of each salient stator pole to produce a rotating magnetic field for low-torque applications.

Copper Shading Ring

A copper ring partially encircling each stator pole in a shaded-pole motor that creates the required phase shift and rotating magnetic field effect for starting.

Split-Phase Motor (Resistance-Start Motor)

A single-phase induction motor utilizing separate main and auxiliary/starting windings with a single-cage rotor, providing low starting torque suited for easily started loads like fans.

Capacitor-Start Capacitor-Run Motor

A single-phase motor using a start capacitor to generate high starting torque and a permanently connected run capacitor to optimize efficiency and power factor during running.

Centrifugal Switch

A switching mechanism in single-phase capacitor motors that automatically disconnects the start capacitor once the rotor reaches its designed operating speed.

Run Capacitor

A capacitor connected permanently in series with the auxiliary winding of a single-phase motor to improve running power factor and operating efficiency.

Universal Motor

A series-wound motor designed to operate on either DC or single-phase AC supplies, delivering high starting torque and variable-speed operation for portable tools and household appliances.

Synchronous Speed Formula

The equation determining the rotational speed of an AC motor's magnetic field: $N_s = \frac{120f}{P}$, where $f$ is frequency in $\text{Hz}$ and $P$ is the total number of magnetic poles.

Induction-Motor Slip Formula

The relative speed difference between synchronous speed $N_s$ and rotor speed $N_r$, defined as $s = \frac{N_s - N_r}{N_s}$ or as percentage $s = \frac{N_s - N_r}{N_s} \times 100\%$.

Induction-Motor Rotor Speed Formula

The equation calculating the actual operating speed $N_r$ of an induction motor rotor given synchronous speed $N_s$ and per-unit slip $s$: $N_r = (1 - s)N_s$.

Squirrel-Cage Rotor

An induction motor rotor composed of conductor bars permanently short-circuited at both ends by end rings, having no external electrical connection via slip rings.

Wound Rotor

An induction motor rotor constructed with insulated wire windings whose ends connect to slip rings, enabling insertion of external resistance to control starting torque.

Slip Rings

Electrically conductive rings mounted on the shaft of a wound-rotor induction motor that connect the internal rotor windings to external adjustable resistors.