Eddy Current: Localized currents induced in an iron core by alternating magnetic flux. These currents translate into losses (heat) and their minimization is an important factor in lamination design.

 
Efficiency: The efficiency of a motor is the ratio of mechanical output to electrical input. It represents the effectiveness with which the motor converts electrical energy into mechanical energy. NEMA has set up codes which correlate to specific nominal efficiencies. A decrease in losses (the elements keeping the motor from being 100% efficient of 10% constitutes an upward improvement of the motor of one code on the NEMA table. Each nominal efficiency has a corresponding minimum efficiency number.

 
Electrical Degree: A unit of measurement of time as applied to alternating current. One complete cycle =360 electrical degrees. One cycle in a rotating electric machine is accomplished when the rotating field moves from one pole to the next pole of the same polarity. There are 360 electrical degrees in this time period. Therefore, in a two pole machine there are 360 degrees in one revolution, and the electrical and mechanical degrees are equal. In a machine with more than two poles, the number of electrical degrees per revolution is obtained by multiplying the number of pairs of poles by 360.
 
 
Electrical Unbalance: In a 3 phase supply, where the voltages of the three different phases are not exactly the same. Measured in % of unbalance.

 
Electromotive Force: (EMF) A synonym for voltage, usually restricted to generated voltage.

 
Encapsulated Winding: A motor which has its winding structure completely coated with an insulating resin (such as epoxy). This construction type is designed for exposure to more severe atmospheric conditions than the normal varnished winding.

 
Enclosures: The housing, frame, of the motor of which there are two broad classifications; open and totally closed. There are specific types of each:

 
Motor Enclosures:

ODP - Open Drip-Proof
TEAO - Totally-Enclosed, Air-Over
TEBC - Totally-Enclosed, Blower-Cooled
TEAAC - Totally-Enclosed, Air to Air Cooled
TEFC - Totally-Enclosed, Fan-Cooled
TENV - Totally-Enclosed Non-Ventilated
TETC - Totally-Enclosed, Tube Cooled
TEWAC - Totally-Enclosed, Water/Air Cooled
TEXP - Totally-Enclosed, Explosion-Proof
WPI - Weather Protected, Type I
WPII - Weather Protected Type II
XP - Explosion-Proof

International:
IP-22 - Open Drip-Proof
IP-44 - Totally-Enclosed
IP-54 - Splash Proof
IP-55 - Washdown

 

Endshield: The part of the motor housing which supports the bearing and acts as a protective guard to the electrical and rotating parts inside the motor. This part is frequently called the "end bracket" or "end bell."

EPAct: The Energy Policy Act of 1992 (EPAct) is an important piece of legislation for efficiency because it established minimum efficiency levels for electric motors manufactured or imported after October 1997. EPAct, which was based on NEMA standards, defined a number of terms, including what constitutes an energy-efficient motor. The DOE issued a rule that defines these motors and how manufactures must comply.
 
Explosion-Proof Enclosure: A totally enclosed enclosure which is constructed to withstand an explosion of a specified gas, vapor or dust which may occur within it. Should such an explosion occur, the enclosure will prevent the ignition or explosion of the gas or vapor which may surround the motor enclosure. These motors are listed with Underwriter's Laboratories.

 
Explosion-Proof-Hazardous Locations
DIVISION I - Location in which ignitable concentrations of flammable or combustible material exist and come in contact with the motor.
DIVISION 11 - Locations in which ignitable concentrations of flammable or combustible material exist but are contained within closed systems or containers and normally would not come in contact with the motor.

EXPLOSION-PROOF-U.L. CLASSIFICATIONS CLASS I -Those in which flammable gasses or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.

Group A - Atmospheres containing acetylene

Group B - Atmospheres containing hydrogen, gases or vapors of equivalent hazard such as manufactured gas
Group C - Atmospheres containing ethyl or ether vapors.
Group D - Atmospheres containing gasoline, hexane, benzene, butane, propane, alcohols, acetone, benzol, lacquer solvent vapors, natural gas, etc.

EXPLOSION-PROOF-U.L. CLASSIFICATIONS Class 11-Those which are hazardous because of the presence of combustible dust.

Group E - Atmospheres containing metal dust, including aluminum, magnesium, or their commercial alloys.
Group F - Atmospheres containing carbon black, charcoal, coal or coke dust.
Group G - Atmospheres containing flour, starch, grain or combustible plastics or chemical dusts.
 
Externally Ventilated: A motor using an external cooling system. This is required in applications where the motor's own fan will not provide sufficient cooling; this is true for certain duty cycle applications, slow speed motors, also in environments with extreme dirt. Often a duct with an external blower is used to bring clean air into the motor's air-intake.