Power Electronics & Electric Drives

	Question
1	Explain why The inner n layer of an SCR is doped with gold. This question has 0 answers so far.
1	A Thyristor string is made up of number of SCRs connected in series and parallel. The string has voltage current ratings of 11KV and 4 KA respectively. The voltage and current ratings of available Thyristors are 1800 V and 1000 A respectively. For a string efficiency of 90% calculate the number of series and parallel connected Thyristors. If series connected Thyristors have maximum difference in off state blocking current be 12mA and maximum difference in their reverse recovery charge be 20uC. Calculate the values of static equalizing resistance and dynamic equalizing capacitance of the string. This question has 0 answers so far.
0	Define the Softness factors terms in connection with SCR. This question has 0 answers so far.
0	Define the PIV terms in connection with SCR. This question has 0 answers so far.
0	Define the Reverse Recovery time terms in connection with SCR. This question has 0 answers so far.
0	Define the Reverse Recovery current terms in connection with SCR. This question has 0 answers so far.
0	Define the Cut-in voltage terms in connection with SCR. This question has 0 answers so far.
0	Explain why Holding current is less than latching current. This question has 0 answers so far.
0	What do you understand by string efficiency? What is its significance? This question has 0 answers so far.
0	Justify the statement "Freewheeling diode improves the power factor of the system'. Give reason. This question has 0 answers so far.
0	What is GTO? Describe its basic structure. This question has 0 answers so far.
0	In a class C commutation circuit, the battery voltage is 150 V, maximumload current is 50 A and thyristor turn off time is 30s. Assume 50% tolerance on turn off time. Find L and C of commutation circuit. This question has 0 answers so far.
0	Explain in brief why two SCRs of same rating when connected in parallel do not share equal currents. Suggest any method to equalize the current and discuss its merits and demerits. This question has 0 answers so far.