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.
Eddy Current Brake: A unit consisting of a rotating member keyed to a straight through, double extension shaft and a field coil assembly. The brake rotor rotates at the speed of the prime mover until the field coil is energized. Rotation of the rotor is slowed by controlling the current in the field coil.
Eddy Current Clutch: A device that permits connection between a motor and a load by electrical (magnetic) means - no physical contact is involved. This method is also used for speed control (by clutch "slippage").
Eddy Current Drive: A unit consisting of a driving member which is the drum assembly, the driven member which is the rotor assembly, and a magnetic member which is the field coil assembly. The driven member is driven by a constant speed AC motor. Control of the eddy current drive is obtained by controlling the current in the field coil.
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.
Electrical Coupling: When two coils are so situated that some of the flux set up by either coil links some of the turns of the other, they are said to be electrically coupled.
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 Time Constant: The ratio of electrical inductance to armature resistance.
Electromotive Force: (EMF) A synonym for voltage, usually restricted to generated voltage. In DC adjustable speed drives, voltage applied to the motor armature from a power supply is the EMF and the voltage generated by the motor is the counter-electromotive force, or CMEF.
Electronic DC Motor Controller: An electronic direct current motor controller is a phase-controlled rectifying system using semi-conductors for power conversion to supply the armature circuit or the armature and shunt field circuits of a direct current motor to provide adjustable speed, adjustable and compensated speed, or adjustable and regulated speed characteristics.
Enable: To allow an action or acceptance of data by applying an appropriate signal to the appropriate input.
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: Enclosure refer to the housing in which the controller is mounted. Enclosures are available in designs for various environmental conditions.
Enclosure Controller NEMA Type 1: A general purpose enclosure of either a ventilated or non-ventilated variety. It is used for most indoor applications and is intended to protect against dust, light, indirect splashing and accidental human contact with the electrical circuit.
Enclosure Controller NEMA Type 4: A watertight enclosure, required whenever the unit is subjected to a great amount of water from any angle. It is normally used in areas that are repeatedly hosed down. This enclosure is not designed to be submerges.
Enclosure Controller NEMA Type 7: An enclosure designed for a hazardous location , Class I (air), Group D, per the National Electrical Code. This hazardous environment is one in which flammable gases or vapor may be present in the air in quantities sufficient to produce explosive or ignitable mixtures. This explosion proof enclosure shall be of such substantial construction that it will withstand the internal pressures resulting from explosions without bursting, permanently distorting, or loosening its joints.
Enclosure Controller NEMA Type 9: An enclosure designed for hazardous locations, Class II, Groups F and G, per the National Electrical Code. The atmosphere in which this controller must operate will contain carbon black, coal or coke dust, flour, starch, or grain dust.
Enclosure Controller NEMA Type 12: Designed for industrial use. The enclosure is intended for use in applications where it is desirable to exclude such materials as cooling oil, seepage, dust, lint, fibers, and filings. This is normally a non-ventilated enclosure with an oil resistant, synthetic gasket between the case and the cover. The cover is hinged to swing horizontally and is held in place with suitable fasteners which require the use of a tool.
Enclosure Motor Dripproof/Open Dripproof (DP/ODP): Horizontal motor term indicating a machine in which the ventilating openings are so constructed that successful operation is not interfered with when drops of liquid, or solid particles, strike, or enter, the enclosure at any angle from 0 to 15° downward from the vertical.
Enclosure Motor Dripproof Guard (DPG): An open dripproof machine in which all openings giving direct access to live metal or rotating parts (except smooth rotating surfaces) are limited in size by the structural parts, or by the screens, baffles, grilles, expanded metal, or other means to prevent accidental contact with hazardous parts. Openings giving direct access to such live or rotating parts shall not permit the passage of a cylindrical rod 0.75 inch in diameter.
Enclosure Motor Explosionproof (XP): A machine designed to withstand an explosion of a specified vapor, gas, or dust, inside the motor casing and prevent the ignition outside the motor by sparks, flashing, or explosion.
Enclosure Motor Pipe Ventilated: Similar to an open dripproof motor except that openings for admission of ventilating air are so arranged that inlet ducts or pipes can be connected to them. Air may be circulated by means integral with the machine or by means external to the machine (separately or forced ventilated).
Enclosure Motor Separately Ventilated (DC Motors): A motor which has a blower attached, or some other cooling equipment, to move air across the unit and keep it below the limiting temperature rise.
Enclosure Motor Splash Proof (DC Motor): An open machine in which the ventilating openings are so constructed that successful operation is not interfered with when drops of liquid or solid particles strike or enter the enclosure at any angle not greater than 100° downward from the vertical.
Enclosure Motor Totally Enclosed Air Over (TEAO): A machine which does not utilize a fan for cooling, but is used in situations where air is being blown over the motor frame for cooling, such as a fan application. When quoting this motor, air velocity in feet per minute must be specified.
Enclosure Motor Totally Enclosed Air-to-Air Machine (TEAAC): A totally enclosed machine which is cooled by circulating the internal air through a heat exchanger which, in turn, is cooled by circulating external air. It is provided with an air-to-air heat exchanger for cooling the internal air, a fan (or fans), integral with the rotor shaft or separate, for circulating the internal air and a separate fan for circulating the external air.
Enclosure Motor Totally Enclosed Fan Cooled (TEFC): A machine which has an enclosure which does not allow for free exchange of air, but still breathes air. A fan is attached to the shaft that pushes air over the frame during operation to help in the cooling process.
Enclosure Motor Totally Enclosed Non-Ventilated (TENV): A totally enclosed machine which does not have means for cooling built into the design. This design requires external cooling provision supplied by an outside source.
Enclosure Motor Totally Enclosed Water Cooled (TEWC): A totally enclosed machine which is cooled by circulating water and with the water or water conductors come in direct contact with the machine parts.
Enclosure Motor Totally Enclosed Water-to-Air Cooled (TEWAC): A totally enclosed machine which is cooled by circulating air which, in turn, is cooled by circulating water. These motors are provided with a water-cooled heat exchanger for cooling the internal and a fan(s), integral with the rotor shaft separate, for circulating the internal air. (Design not offered by USEM, but is a GE product.)
Enclosure Motor Washdown Duty: A machine designed specifically for the food processing industry and other applications that are routinely exposed to washdown, chemicals, humidity, and other severe environments.
Enclosure Motor Weather Protected I (WPI): A vertical or large horizontal machine which has ventilating passages constructed to minimize the entrance of rain, snow, airborne particles and prevent passage of a 0.75 inch diameter cylindrical rod.
Enclosure Motor Weather Protected II (WPII): A machine which has the protection of a weather protected I machine plus the normal path of the ventilating air which enters the electric parts of the machine so arranged so that there are at least 3 abrupt changes in direction, none of which is less than 90° . In addition, an area of low velocity not exceed 600 feet per minute shall be provided in the intake air path to minimize the possibility of moisture or dirt being carried into the electric parts of the machine.
Encoder: An electromechanical transducer that produces a serial or parallel digital indication of mechanical angle or displacement. Essentially, an encoder provides high resolution feedback data related to shaft position and is used with other circuitry to indicate velocity and direction. The encoder produces discrete electrical pulses during each increment of shaft rotation.
End Bells: Also called end shields, cover plates, etc., used to support bearings or to cover the windings. On small motors the end bell is a complete cover, with a few openings for cooling. On large motors, when the bearings are not part of the end shield, a perforated cover may leave the rotor exposed, and only the stator windings are protected.
Endshield: That 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".
Equilibrium Torque: The torque required by a load that will not cause a motor to become unstable. High 20% "buffer" between load and rated allowable load.
Excitation Current: A term usually applied to the current in the shunt field of a motor resulting from voltage applied across the field.
Explosionproof Divisions: The first classification of explosionproof motors as developed by the National Electrical Code (NEC). Divisions divide the motor environment into areas where the danger of explosion is always present (division 1) and areas where only under certain conditions is the danger of explosion present (division 2).
Explosionproof Groups: The third classification of explosionproof motors as developed by the National Electrical Code (NEC). Groups divide the motor classes even further by grouping together similar liquids, vapors, dusts, and flyings.
Explosionproof Labels: In electric motors the explosionproof label describes whether the motor is good for liquids only, or for liquids, vapors, dusts, and flyings.
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