Electric motor: Difference between revisions

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'''Electric motors''' in the era of Edison, Westinghouse, and Tesla were considered mysterous; followed by a long era of being a commodity. Now that motors are controlled by software they are the center of intense reseach.
An '''electric motor''' converts [[electrical energy]] into [[mechanical energy]]. The reverse process, that of converting mechanical energy into electrical energy, is accomplished by a [[Electrical generator|generator]] or dynamo. Most electric motors work by [[magnetism|electromagnetism]], but motors based on other electromechanical phenomena, such as [[electrostatic motor|electrostatic forces]] and the [[piezoelectric effect]] and thermal motors, also exist. The fundamental principle upon which electromagnetic motors are based is that there is a [[Lorenz force|mechanical force]] on any current-carrying wire contained within a magnetic field. The force is described by the [[magnetic field|Lorentz force law]] and is perpendicular to both the wire and the magnetic field.


There is much confusing and contradicting published material about electric motors. Also, motors bridge the skills of electrical and mechanical engineers as exemplified by the equation p = iv = Γ ω.
Most magnetic motors are rotary, but [[linear motor]]s also exist. In a rotary motor, the rotating part (usually on the inside) is called the [[Rotor (electric)|rotor]], and the stationary part is called the [[stator]]. The rotor rotates because the wires and magnetic field are arranged so that a [[torque]] is developed about the rotor's axis. The motor contains [[electromagnet]]s that are wound on a frame. Though this frame is often called the [[armature (electrical engineering)|armature]], that term is often erroneously applied. Correctly, the armature is that part of the motor across which the input [[voltage]] is supplied. Depending upon the design of the machine, either the rotor or the stator can serve as the armature.
 
Even more exciting is that electric motors inherently rely on relative motion ( and so ultimatlely on the special theory of relativity). This is why the myth of AC and DC motors exists, but mathematicaly there is only one. A motor will have a power supply that is either AC or DC. The next physical distinction states is/are the stator and rotor currents AC or DC as a permutation.
 
If both currents are DC, this is the classic brushed DC motor supplied by a battery.
 
If one is DC and the other is AC (with respect to the stator and rotor does not matter which is which) this is a synchonous motor.
 
If both are AC, this is a true AC motor( Tesla, rest in peace).
 
Now with digital control a software program can write to a motor as if it were paper moving in space.

Revision as of 00:33, 19 November 2007

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An electric motor converts electrical energy into mechanical energy. The reverse process, that of converting mechanical energy into electrical energy, is accomplished by a generator or dynamo. Most electric motors work by electromagnetism, but motors based on other electromechanical phenomena, such as electrostatic forces and the piezoelectric effect and thermal motors, also exist. The fundamental principle upon which electromagnetic motors are based is that there is a mechanical force on any current-carrying wire contained within a magnetic field. The force is described by the Lorentz force law and is perpendicular to both the wire and the magnetic field.

Most magnetic motors are rotary, but linear motors also exist. In a rotary motor, the rotating part (usually on the inside) is called the rotor, and the stationary part is called the stator. The rotor rotates because the wires and magnetic field are arranged so that a torque is developed about the rotor's axis. The motor contains electromagnets that are wound on a frame. Though this frame is often called the armature, that term is often erroneously applied. Correctly, the armature is that part of the motor across which the input voltage is supplied. Depending upon the design of the machine, either the rotor or the stator can serve as the armature.

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