i want to know 3 things.if anyone can help me i will be so thankful.
1.why scr does not latch in ac circuit
2.how to control high voltage using scr
3.how to control load current using scr

 

check this out

http://en.wikipedia.org/wiki/Silicon-controlled_rectifier

and look up triacs, they are like two scrs back to back for ac power control

http://en.wikipedia.org/wiki/Triac

 

no result..i looked at them...they are not giving my ans clearly

 

for the first question i'd say it would be good to post the circuit, the question is worded in a tricky way.

for the second question controlling high voltage is no different from controlling low voltage except you would use a high voltage scr.

for the third question i'd say the scr doesnt really control current it simply conducts at a set part of the input waveform which in turn will change the average current and voltage delivered to the given load.

i was aware that the given text didn't directly answer you questions but i thought it would be easier to come to a conclusion if you knew the theory of the device in question.

hope this helps

 

Here is a link to the AAC ebook on the topic of SCRs.

hgmjr