Answer / praveen

breaker capaciy taken by 132kv for example 133*1.55 times
capacity 145kv suitable for beaker

Answer / raghavendran.r

Step1: Calculate the system MVA.I have calculated that as 1.732*6600*800 = 9.144MVA. I have taken it as 10 MVA for easy calculations further.From the system MVA find out the Fault MVA value using the per unit impedance.i.e

Fault MVA = System MVA /P.u.Impedance.I am taking iot as .1
Hence we arrive at the Fault MVA.From this condition we get to know the Short circuit current as Isc = Fault MVA/Sys Voltage(6.6kV).

Usually, for a 6.6 kV system, the short circuit withstand rating is 40kA for 1 second.The Momentary current or making current is 2.55 times the Max. short circuit current.hHence we arrive at 100kA(Peak)

i am swathi, b.tech 4th year. In smps(switched mode power supply)we are using diodes,mosfets,igbts for controling of current. And my question is why we did not use thyristors(scr)? it is also act as a switch,then what is the drawback of scr as compared to above transisters> if we use the scr,then what is happening ? plz give reply as soon as possible bcoz i am doing project on smps. plz frnds i want ans for that. if anybody know the ans plz send to my e-mail id /swathi.tadakapally@gmail.com/

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