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Formation of arc during circuit breaking The phenomena of Arc During opening of current carrying contacts in a circuit breaker the medium in between opening contacts become highly ionized through which the interrupting current gets low resistive path and continues to flow through this path even after the contacts are physically separated. During the flowing of current from one contact to other the path becomes so heated that it glows in the form of an arc.Arc in circuit breaker Whenever, the contacts of circuit breaker open while carrying load there is an arc in the medium between the separating contacts of the circuit breaker. As long as this arc is sustained in between the contacts, the current through the circuit breaker will not be interrupted totally.For total interruption of current, the arc needs to be quenched as quickly as possible. The main designing criteria of a circuit breaker is to provide appropriate technology of arc quenching in circuit breaker to fulfill quick and...

Circuit Breaker Circuit breakers provide a manual means of energizing and de-energizing a circuit. Unlike fuses, which must be replaced when they open, a circuit breaker can be reset once the overcurrent condition has been corrected. Pushing the handle to the “OFF” position then back to the “ON” position restores the circuit. If a circuit reopens upon reset to the “ON” position, the circuit should be checked by a qualified electrician. The fundamental of Circuit breaker operation In the following illustration, an AC motor is connected through a circuit breaker to a voltage source. When the circuit breaker is closed, a complete path for current exists between the voltage source and the motor allowing the motor to run. Opening the circuit breaker breaks the path of current flow and the motor stops. The circuit breaker automatically opens when it senses a fault Circuit breaker

Zener diodes If we connect a diode and resistor in series with a DC voltage source so that the diode is forward-biased, the voltage drop across the diode will remain fairly constant over a wide range of power supply voltages: According to the " diode equation," the current through a forward-biased PN junction is proportional to  e  raised to the power of the forward voltage drop. Because this is an exponential function, current rises quite rapidly for modest increases in voltage drop. Another way of considering this is to say that voltage dropped across a forward-biased diode changes little for large variations in diode current. In the circuit shown above, diode current is limited by the voltage of the power supply, the series resistor, and the diode's voltage drop, which as we know doesn't vary much from 0.7 volts. If the power supply voltage were to be increased, the resistor's voltage drop would increase almost the same amount, and the diode's ...

Introduction Electronic Diode A  diode  is an electrical device allowing current to move through it in one direction with far greater ease than in the other. The most common type of diode in modern circuit design is the semiconductor  diode, although other diode technologies exist. Semiconductor diodes are symbolized in schematic diagrams as such: When placed in a simple battery-lamp circuit, the diode will either allow or prevent current through the lamp, depending on the polarity of the applied voltage: When the polarity of the battery is such that electrons are allowed to flow through the diode, the diode is said to be  forward-biased . Conversely, when the battery is "backward" and the diode blocks current, the diode is said to be  reverse-biased . A diode may be thought of as a kind of switch: "closed" when forward-biased and "open" when reverse-biased. Oddly enough, the direction of the diode symbol's "arrowhead" ...

Amplifiers The practical benefit of active devices is their amplifying  ability. Whether the device in question be voltage-controlled or current-controlled , the amount of power required of the controlling signal is typically far less than the amount of power available in the controlled current. In other words, an active device doesn't just allow electricity to control electricity; it allows a  small  amount of electricity to control a  large  amount of electricity. Because of this disparity between  controlling  and controlled  powers, active devices may be employed to govern a large amount of power (controlled) by the application of a small amount of  (adsbygoogle = window.adsbygoogle || []).push({}); power (controlling). This behavior is known as amplification . It is a fundamental rule of physics that energy can neither be created nor destroyed. Stated formally, this rule is known as the Law of Conservation of Energy, and n...

Mutual inductance and basic operation Suppose we were to wrap a coil of insulated wire around a loop of ferromagnetic material and energize this coil with an AC voltage source: As an inductor, we would expect this iron-core coil to oppose the applied voltage with its inductive reactance, limiting current through the coil as predicted by the equations X L  = 2 p fL and I=E/X (or I=E/Z). For the purposes of this example, though, we need to take a more detailed look at the interactions of voltage, current, and magnetic flux in the device. . (adsbygoogle = window.adsbygoogle || []).push({}); Kirchhoff's voltage law describes how the algebraic sum of all voltages in a loop must equal zero. In this example, we could apply this fundamental law of electricity to describe the respective voltages of the source and of the inductor coil. Here, as in any one-source, one-load circuit, the voltage dropped across the load must equal the voltage supplied by the source, assuming zero vol...

Introduction  After the introduction of the DC electrical distribution system by Edison in the United States, a gradual transition to the more economical AC system commenced. Lighting worked as well on AC as on DC. Transmission of electrical energy covered longer distances at lower loss with alternating current. However, motors were a problem with alternating current. Initially, AC motors were constructed like DC motors. Numerous problems were encountered due to changing magnetic fields, as compared to the static fields in DC motor motor field coils.  Charles P. Steinmetz contributed to solving these problems with his investigation of hysteresis losses in iron armatures. Nikola Tesla envisioned an entirely new type of motor when he visualized a spinning turbine, not spun by water or steam, but by a AC induction motor,is the workhorse of industry to this day. Its ruggedness and simplicity make for long life, high reliability, and low maintenance. Yet small brushed AC...