electric motor

(redirected from Electromotor)
Also found in: Dictionary, Thesaurus, Wikipedia.

motor, electric,

machine that converts electrical energy into mechanical energy. When an electric current is passed through a wire loop that is in a magnetic field, the loop will rotate and the rotating motion is transmitted to a shaft, providing useful mechanical work. The traditional electric motor consists of a conducting loop that is mounted on a rotatable shaft. Current fed in by carbon blocks, called brushes, enters the loop through two slip rings. The magnetic field around the loop, supplied by an iron core field magnet, causes the loop to turn when current is flowing through it. In an alternating current (AC) motor, the current flowing in the loop is synchronized to reverse direction at the moment when the plane of the loop is perpendicular to the magnetic field and there is no magnetic force exerted on the loop. Because the momentum of the loop carries it around until the current is again supplied, continuous motion results. In alternating current induction motors the current passing through the loop does not come from an external source but is induced as the loop passes through the magnetic field. In a direct current (DC) motor, a device known as a split ring commutator switches the direction of the current each half rotation to maintain the same direction of motion of the shaft. In any motor the stationary parts constitute the stator, and the assembly carrying the loops is called the rotor, or armature. As it is easy to control the speed of direct-current motors by varying the field or armature voltage, these are used where speed control is necessary. The speed of AC induction motors is set roughly by the motor construction and the frequency of the current; a mechanical transmission must therefore be used to change speed. In addition, each different design fits only one application. However, AC induction motors are cheaper and simpler than DC motors. To obtain greater flexibility, the rotor circuit can be connected to various external control circuits. Most home appliances with small motors have a universal motor that runs on either DC or AC. Where the expense is warranted, the speed of AC motors is controlled by employing special equipment that varies the power-line frequency, which in the United States is 60 hertz (Hz), or 60 cycles per second. Brushless DC motors are constructed in a reverse fashion from the traditional form. The rotor contains a permanent magnet and the stator has the conducting coil of wire. By the elimination of brushes, these motors offer reduced maintainance, no spark hazard, and better speed control. They are widely used in computer disk drives, tape recorders, CD drives, and other electronic devices. Synchronous motors turn at a speed exactly proportional to the frequency. The very largest motors are synchronous motors with DC passing through the rotor.

Electric Motor

 

a machine that converts electrical energy into mechanical energy. The electric motor is a basic type of motor used in industry, transportation, homes, and elsewhere. Electric motors can be classified by the kind of current used for their drive. The DC motors have the advantage of an economical and smooth regulation of their rotational speed (rpm). The AC motors include synchronous and asynchronous electric motors. In a synchronous motor the rotational speed (rpm) is rigidly dependent on the frequency of the feeder current. In an asynchronous motor the rotational speed decreases as the load increases. A third type of alternating current motor is the commutator motor, which permits a smooth regulation of rotational speed within wide limits.

The asynchronous motor is the most widely used; it is simple to manufacture and is reliable in operation (particularly the squirrel-cage motors). Their main disadvantages are a considerable consumption of reactive power and the lack of a smooth (gradual) speed regulation. In many high-power electric drives, synchronous electric motors are being used. DC motors are utilized if speed regulation is of paramount importance; the more expensive and less reliable AC commutator motors are very occasionally used in these cases. The power rating of electric motors ranges from a fraction of a watt to dozens of megawatts. Electric motors have various forms of frame construction: open frame, in which the rotating and current-carrying parts are protected against accidental touching and foreign objects; protected frame (including drop-proof and spray-proof designs); closed frame (dust-proof and moisture-proof); hermetic frame; and explosion-proof frame (in case of an explosion of gases inside the motor, any flame is confined to the interior of the motor housing).

electric motor

[i¦lek·trik ′mōd·ər]
(electricity)
References in periodicals archive ?
ceiling - 3000 m with fully charged batteries Motor type LEM, brush EM 42, brushless DC/DC electromotor electromotor Motor power 18 kW 42 kW Motor weight ca 8,5 kg approx.
Debris generated after electromotor's burning out as well as compressor lubricating oil combustion products remain in the Freon section of the heat pump's cooling system causing new damage of electromotor and vital parts of the compressor.
For determine those three case, we can control the relevant cams by using of several electro mechanical devices such as magnetic, electromotor and pneumatic forces.
Manualexertion of force was automated to increase the couple with a constant rate by installation of a motorreductor--i.e., a combination of an electromotor and a reduction case.
20 out of 32 crystallographic point groups are piezoelectric).The very basis of functional biological systems is electromechanics--from nerve-controlled muscle contraction on the macroscale, to cardiac activity and hearing on the micron scale, to energy storage in mitochondria, voltage-controlled ion channels, and electromotor proteins on the nanoscale.
A rotating axle driven by an electromotor, located exactly at the middle of the axle, has two holed discs at its extremities.
La senal de comando para la generacion de la DOE es iniciada en un nucleo unico bulbar (nucleo marcapaso, nucleo electromotor bulbar), cuyas celulas poseen las propiedades funcionales de marcapasos celulares (Bennet y cols., 1967; Dye y Meyer, 1986).
The first recorded instance of intraoperative testing may be the electromotor test developed by Burge and Vane in 1958 (1) to assess the completeness of vagotomy in patients undergoing antrectomy because of gastric ulcer disease.
The company says it will display city buses that will be powered by an internal combustion engine and an electromotor.
When the channels are transiently opened, short influxes of sodium pass through, leading to an electromotor gradient that is opposed to the resting potential of the membrane, which then builds up the action potential necessary for impulse conduction.
The electromotor system of Torpedo is a well-established model for studies on the chemistry of cholinergic synaptic transmission (for review see Whittaker, 1992).