4 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



3.35 amperes and a power of 2960 watts, when the voltage 

 impressed on the high-tension side is 11,000 volts at 60 cycles. 

 What current and power will this transformer take at no load if 

 12,700 volts at 60 cycles is impressed on the high-tension winding? 

 Assume that the core loss varies as the 1.7 power of the flux 

 density. 



16.' A 50-kv.-a. transformer takes a current of 0.1 ampere and 

 a power of 641 watts at no load when 30,000 volts at 50 cycles is 

 impressed on the high-tension winding. What current and power 

 will this transformer take at no load if 30,000 volts at 60 cycles is 

 impressed on the high-tension winding? Assume that the core 

 loss varies as the 1.3 power of the frequency and the 1.7 power of 

 the flux density. 



17. The resistance to direct current of a reactor which has a 

 laminated magnetic circuit is 0.2 ohm. When 110 volts at 60 

 cycles is impressed on this reactor the current is 10 amperes and 

 the power is 550 watts. What are the apparent resistance and 

 reactance of the reactor? What is the actual inductance of the 

 reactor at this voltage and frequency? 



18. l When 110 volts at 60 cycles is impressed on a reactor 

 which has a laminated magnetic circuit it absorbs 500 watts. At 

 this time the inductance of the reactor is 25 mil-henrys and the 

 resistance is negligibly small, (a) What are the current and 

 power factor? What are the apparent resistance and reactance 

 of the reactor? (b) If 146 volts at 60 cycles is impressed on 

 this reactor what will be the current and power factor? What 

 will be the apparent resistance and reactance of the reactor? 

 Assume that the iron loss varies as the 1.7 power of the flux 

 density. 



19. A reactor with a laminated magnetic circuit has a negligibly 

 small resistance to direct current. When 110 volts at 25 cycles 

 is impressed on this reactor the current is 20 amperes and the 

 power is 1000 watts. If a very small air-gap is cut in the mag- 



1 Assume that the orignal flux density is 70 kilolines per sq. in., and that 

 the relation between the flux density and the permeability for this quality 

 of iron is expressed by : 



=102-0.017/< 



between B equals 45 kilolines and B equals 95 kilolines per sq. in. In prob- 

 lems where this applies the effect of the joints in the magnetic circuit will 

 be neglected. 



