October 2008
You are currently browsing the articles from circuitmaniac.com written in the month of October 2008.
Electromagnetic attraction relays operate by virtue of an armature being attracted to the poles of an electromagnet or a plunger being drawn into a solenoid. Such relays may be actuated by d.c. or a.c quantities. The important types of electromagnetic attraction relays are: (i) Attracted armature type relay – Fig 3 shows the schematic arrangement [...]
Written by John on October 30th, 2008 with 1 comment.
Read more articles on classification of relays and Power System and Relays and Switchgear&Protection.
The relays used in the power system operate by virtue of the current or voltage supplied by the current and voltage transformers connected in various combinations to the system element that is to be protected. Through the individual or relative changes in these two quantities, faults signal their presence, type and location to the protective [...]
Written by John on October 30th, 2008 with 2 comments.
Read more articles on classification of relays and Power System and Relays and Switchgear&Protection.
The principle function of protective relaying is to cause the prompt removal from service of any element of the power system when it starts to operate in an abnormal manner or interfere with the effective operation of the rest of the system. In order that protective relay system may perform this function satisfactorily, it should [...]
Written by John on October 30th, 2008 with no comments.
Read more articles on Power System and Relays and requirement of protective relaying and Switchgear&Protection.
When failure occurs on any part of the system it must be quickly detected and disconnected from the system for two reasons. Firstly if fault is not cleared it may cause unnecessary interruption of service to the customers. Secondly the rapid disconnection prevents the damage and spreading of fault into the system. The detection of [...]
Written by John on October 30th, 2008 with no comments.
Read more articles on Power System and Relays and Switchgear&Protection.
TYPES OF PROTECTION When fault occurs in any part of system, it must be cleared quickly to avoid damage or interference with rest of the system. Protection scheme is divided into two classes- primary protection and back up protection. Primary protection It’s used for protection of component parts of power system. In fig 1 each [...]
Written by John on October 30th, 2008 with no comments.
Read more articles on Power System and Relays and Switchgear&Protection and Types of relay protection.
The cross sectional view of a diac showing all its layers and junction is shown above figure.Diac is a two electrode device,it can conduct in either direction.Terminals are denoted by T1 and T2.word diac stands for ‘diode for ac‘.The four layer are pn pn and pn pn’. Symbol Principle of Operation When T1 is positive [...]
Written by John on October 19th, 2008 with no comments.
Read more articles on DIAC and Power Electronics.
From the above characteristics,latching current for large power GTO is several amperes here 2A as compared to 100-500mA for conventional thyristors of same rating.If gate current is not able to turn on the GTO,it behaves like a high voltage,low gain transistor with considerable anode current.This leads to a noticable power loss under such conditions. Share [...]
Written by John on October 18th, 2008 with no comments.
Read more articles on Gate Turn Off Thyristor and Power Electronics.
Advantages of GTO over Thyristor Commutation circuit is not needed Fast switching speed More di/dt at turn on Higher efficiency because losses in commutation circuit is eliminated Circuits using GTO are compact Lesser acoustical and electromagnetic noise due to elimination of choke of commutation Disadvantages of GTO Higher latching and holding current Higher on state [...]
Written by John on October 18th, 2008 with 4 comments.
Read more articles on Gate Turn Off Thyristor and Power Electronics.
The voltage and current wave forms of a GTO is show in figure below.The positive and negative pulses are shown. When a positive signal is applied,GTO starts conducting.Before initiation of conduction anode current(iA)is zero and anode- cathode voltage VAK is the peak reverse voltage.When conduction starts rises iA to full value and the VAK becomes [...]
Written by John on October 18th, 2008 with no comments.
Read more articles on Gate Turn Off Thyristor and Power Electronics.
GTO is a special thyristor which can be turned on by a positive gate signal and can be turned off by a neagative signal.Evidently the use of GTO in power electronic circuit eliminates the need of forced commutation circuit because turnoff is achieved by applying a negative circuit. The two transistor analogy of a GTO [...]
Written by John on October 18th, 2008 with no comments.
Read more articles on Gate Turn Off Thyristor.
ABSTRACT Piezoelectric ultrasonic motors were heard past from about 30 years.Today large number of designs have been developed on Piezoelectric ultrasonic motors.Different working principles of this kind of motors have dealt in this paper.The operational stages of Piezoelectric ultrasonic motors is well explained in this paper.Their advantages ,disadvantages,economical and others perspectives are well studied and [...]
Written by John on October 17th, 2008 with 2 comments.
Read more articles on piezoelectric motor and Reference Papers.
Bipolar junction transistor have low power losses but have long switching time.(especially at turnoff).MOSFETs have very fast switching characteristics(low turn on and turn off times)but have higher power losses.IGBT combines the advantages of MOSFET and BJT.Thus an IGBT has low switching times as well as low power losses.Its called as IGBT or GEMET or COMFET(conductivity [...]
Written by John on October 17th, 2008 with 2 comments.
Read more articles on IGBT and Power Electronics.
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