EEE343: Electro-Mechanical Devices and Machines I Practice Flashcards

These flashcards cover the fundamental principles of electro-mechanical energy conversion, system modeling, loss types, magnetic circuit formulas, and the specific construction and classification of DC machines based on the lecture notes.

Principle of Energy Conservation

The fact that energy can neither be created nor destroyed, but can only change from one form to another.

Motoring Operation

An electromechanical process involving the conversion of electrical energy (input) into mechanical energy (output).

Generating Operation

An electromechanical process involving the conversion of mechanical energy (input) into electrical energy (output).

Transducers

Devices used solely for energy conversion in measurement and control environments, where signals are converted into another form of energy for process control; sometimes referred to as MEMS (Micro Electro-Mechanical System).

Force Generating Devices

A category of devices, including solenoids, actuators, and relays, that convert electrical energy into linear or angular displacement.

Continuous Energy-Conversion Devices

Electrical machines, specifically motors and generators, that rotate continuously for the period of excitation.

Singly Excited System

A system that has only one source of excitation or one coil, often responsible for linear or angular displacement via a coupling field.

Multiple Excited System

Systems with more than one source of excitation or having two or more coils for the excitation process, such as a double excited system.

Coupling Field

The medium of conversion (magnetic or electric field) through which the electromechanical energy conversion process occurs.

General Energy Balance Equation

$$E_{\text{input}} = E_{\text{output}} + E_{\text{stored}} + E_{\text{loss}}$$

Induced Voltage ($e$)

The voltage transferred or induced e.m.f., defined as $e = \frac{d\lambda}{dt}$ where $\lambda$ represents flux linkage ($N\phi$).

$I^2R$ Loss

The electrical energy loss occurring in the windings of a machine, also known as ohmic loss.

Friction and Windage Losses

Mechanical losses associated with the mechanical port (shaft) of an electro-mechanical system.

Core-losses

Heat-related losses associated specifically with the coupling field unit of an electro-mechanical conversion system.

Permeance ($\mathcal{P}$)

A characteristic of the magnetic circuit defined as $\mathcal{P} = \frac{\mu \mu_o A}{l_g}$, where $\mu$ is relative permeability, $\mu_o$ is free space permeability, $A$ is cross-sectional area, and $l_g$ is air gap length.

Coil Inductance ($L$)

A property defined as $L = N^2 \mathcal{P}$, which relates flux linkage to current.

Magnetic Field Energy ($E_f$)

The energy stored in the magnetic field, expressed as $E_f = \frac{1}{2} L i^2$ or $E_f = \frac{1}{2} F \phi$.

Mechanical Force ($F_s$)

The force offered against a stretched spring in a linear system, defined as $F_s = \frac{1}{2} i^2 \frac{dL}{dx}$.

Yoke (Frame)

The part of a DC machine that offers mechanical support for poles and protects the machine from moisture and dust, typically made of cast iron, cast steel, or rolled steel.

Pole Shoe

An enlargement of the pole core in a DC machine that spreads flux within the air-gap and reduces power loss by using annealed steel laminations.

Armature Core

A component with slots that houses the armature conductor and provides a low-reluctance path for the flux generated by field windings.

Commutator

A component built with hard-drawn copper segments and thin mica layers that collects current from the armature and ensures uni-directional torque.

Brushes

Rectangular components made of graphite or carbon that gather current from the commutator to supply an exterior load.

Shunt Wound DC Machine

A DC machine where the field coils are connected in parallel with the armature.

Series Wound DC Machine

A DC machine where the field coils are connected in series through the armature, typically using few turns of wire with a large cross-sectional area.

Compound Wound DC Machine

A machine including both series and shunt fields on every pole; classified as 'short shunt' or 'long shunt' based on connection.

EMF Equation of DC Machine

The equation used to determine the voltage produced: $E = n \cdot P \cdot \Phi \cdot \frac{Z}{A}$, where $n$ is speed, $P$ is poles, $\Phi$ is flux, $Z$ is total conductors, and $A$ is parallel lanes.