Th e rela y show n i n Fig . P7.10 7 connect s th e 3 0 V dc PRACTICAL generato r t o th

Chapter 7, Problem 7.107

(choose chapter or problem)

Th e rela y show n i n Fig . P7.10 7 connect s th e 3 0 V dc PRACTICAL generato r t o th e d c bu s a s lon g a s th e rela y current PERSPECTIV E b & J is greater than 0.4 A. If the relay current drop s to 0. 4 A o r less , th e spring-loade d rela y immediately connect s th e d c bu s t o th e 3 0 V standb y battery . The resistanc e o f th e rela y windin g i s 6 0 ft. Th e induc - tanc e o f th e rela y windin g i s t o b e determined. a ) Assum e th e prim e moto r drivin g th e 3 0 V dc generato r abruptl y slow s down , causin g th e gen - erate d voltag e t o dro p suddenl y t o 2 1 V . What valu e o f L wil l assur e tha t th e standb y battery wil l b e connecte d t o th e d c bu s i n 0. 5 seconds? b ) Usin g th e valu e o f L determine d i n (a) , state ho w lon g i t wil l tak e th e rela y t o operat e if the generate d voltag e suddenl y drop s t o zero. Figure P7.107 30 V r v , *en ^ (R,L) DC