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 ratio of power output to power input.
Electrical Degree: A unit of measurement of time as applied to alternating current. One complete cycle equals 360 electrical degrees. One cycle in a rotating electrical 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 Time Constant (te) (Seconds) : The time required for current to reach 63.2% of its final value for a fixed voltage level. Can be calculated from the relationship te=L/R where L is inductance (henries) and R is resistance (ohms).
Electrical Unbalance: In a three-phase supply, where the voltages of the three different phases are not exactly the same. Measured as a percent of unbalance.
Electromotive Force (F): 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.
Enclosure: The housing or frame of the motor.
Encoder: A feedback device which converts mechanical motion into electronic signals. The most commonly used, rotary encoders, output digital pulses corresponding to incremental angular motion. For example, a 1000-line encoder produces 1000 pulses every mechanical revolution. The encoder consists of a glass or metal wheel with alternating transparent and opaque stripes, detected by optical sensors to produce the digital outputs.
Enshield: 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.
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 would 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-U.L. Classifications: CLASS I Those in which flammable gasses or vapors are or may be present in the air in quantities sufficient to product explosive or ignitable mixtures. Group C Atmospheres containing ethyl or ether vapors. Group D Atmospheres containing gasoline, hexane, benzene, butane, propane, alcohol, acetone, benzol, lacquer solvent vapors, natural gas, etc. CLASS II 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. These cooling system are used in certain duty cycle applications, with slow speed motors, or in environments with extreme dirt. Often a duct with an external blower is used to bring clean air into the motor's air-intake.
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