TRANSFORMERS 



This data is for a good grade of sheet steel. 



For all of the problems to which this data applies assume that at the 

 working flux density the joints in the magnetic circuit require 75 additional 

 ampere turn<. 



12. The magnetic circuit of a 5000-kv.-a. transformer has a 

 mean length of 140 in. and an average cross-section of 613 sq. 



in. The number of turns in the high-tension winding is such that 

 with the rated voltage of 52,000 volts at 50 cycles impressed on 

 this winding, 17,500 watts is supplied at no load. How many 

 turns has the hijrh-tension winding? What are the no-load cur- 

 rent ;md power factor? Use the magnetic data given in problem 

 10. Assume that the core loss at 50 cycles is 80 per cent, of the 

 it 60 cycles. 



13. [f the transformer described in problem \'2\< connected to 

 a 66,000-volt, 50-cycle circuit, what will be the no-load current 

 and power? 



14. The magnetic circuit of a lOOO-kv.-a. transformer has a 

 length of \*:> in. and an average cross-section of 278 sq. in. 



This transformer u droned to operate from a 66,000-volt. 



le circuit. If the maximum flux density is to be 70,000 



<quaro inch how many turns should the hiph-ten<im 



winding have'.' What are the no-load current and power? Use 



the magnetic data given in problem 10. 



15. ' At no load a 500-kv.-a. Iran-former takefl a current of 



tli.-it the orifiiuJ ih density b 70 kiioUnet per *q, m., and that 



tlir rrl.-ition between the flux d Micahility fi.r thi- quality 



ssed by: 



102-0.017* 



. Ulnlllirs :itnl /' '." kllulinc.-, per ^|. III. Inpl'olt- 



tln- :ip|ilirs ..f the joint- in ih. ,,t will 



