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A relay allows circuits to be switched by electrical equipment: for example, a timer circuit with a relay could switch power at a preset time. For many years relays were the standard method of controlling industrial electronic systems. A number of relays could be used together to carry out complex functions (relay logic). The principle of relay ...
In the armature, an electromotive force is created by the relative motion of the armature and the field. When the machine or motor is used as a motor, this EMF opposes the armature current, and the armature converts electrical power to mechanical power in the form of torque, and transfers it via the shaft. When the machine is used as a ...
AC relay with shading coil (red arrow near top) for operating with AC. A shading coil or shading ring (Also called Frager spire or Frager coil) is one or more turns of electrical conductor (usually copper or aluminum) located in the face of the magnet assembly or armature of an alternating current solenoid. The alternating current in the ...
The utilization of the binary properties of electrical switches to perform logic functions is the basic concept that underlies all electronic digital computer designs. Shannon's thesis became the foundation of practical digital circuit design when it became widely known among the electrical engineering community during and after World War II .
A few million reed relays were used from the 1930s to the 1960s for memory functions in Bell System electromechanical telephone exchanges. [2] Often a multiple-reed relay was used, with one of the reeds latching the relay, and the other or others performing logic or memory functions.
In electrical engineering, a stepping switch or stepping relay, also known as a uniselector, is an electromechanical device that switches an input signal path to one of several possible output paths, directed by a train of electrical pulses. The major use of stepping switches was in early automatic telephone exchanges to route telephone calls ...
A hacksaw blade is commonly used as a feeler. The alternating magnetic field induced by a shorted armature is strong at the surface of the armature, and when the feeler is lightly touched to the iron core of an armature winding, small currents are induced in the feeler that generate a third alternating magnetic field surrounding the feeler.
The digital/numeric relay was invented by George Rockefeller. [2] George conceived of it in his Master's Thesis in 1967–68 at Newark College of Engineering. [3] He published his seminal paper Fault Protection with a Digital Computer [4] in 1969. Westinghouse developed the first digital relay with the Prodar 70 [5] being developed between 1969 ...