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. read more

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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 voltage drop and power losses Higher gate current Higher gate circuit losses Lower reverse voltage blocking capacity Inspite of all above disadvantages,GTOs are being used in a variety of application such as variable frequency inverter circuits,electric traction and steel mills.Rating available are upto about 6kV and 6kA. read more

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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 very small(equal to on state voltage drop which is about 1V or so).when a negative gate signal is applied,the anode current becomes zero and the VAK rises to peak reverse voltage. The total turnoff time is composed of three distinct times,storage time(ts ),fall time(tf) and tail time(tt). Initiation of turn off process starts immediately on the application of negative gate signal.  The time elapsing between application of negative gate read more

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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 Two transistor analogy of transistor is shown in figure below When a positive signal is applied,a GTO switches into conduction state like the ordinary thyristor.However in ordinary thyristor the current gains of NPN and PNP transistors are very high so that gate sensitivity for turn on is very high and on state voltage drop is low.However in GTO,the current gai of PNP transistor is low so that turn of fis possible if significant current is drawn from the gate.When a read more

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