PROBLEMS IN ALTERNATING 

 CURRENT MACHINERY 



CHAPTER I 

 TRANSFORMERS 



1. The iron loss in a reactor is 240 watts of which 48 watts is 

 due to eddy currents. If the amount of iron in the magnetic 

 circuit were doubled by doubling the cross-section of the core, 

 what would be the iron loss for the same impressed voltage and 

 frequency? Neglect the resistance drop. 



2. The iron loss in a reactor is 312 watts of which 86 watts is 

 due to eddy currents. If a similar reactor were constructed in 

 which laminations of twice the thickness were used, what would 

 be the iron loss for the same impressed voltage and frequency? 

 Neglect the resistance drop. 



3. When 110 volts at 30 cycles is impressed on a reactor the 

 iron loss is 276 watts of which 204 watts is due to hysteresis. If 

 the impressed voltage and frequency are both doubled what will 

 be the iron loss? Neglect the resistance drop. 



4. When 110 volts at 60 cycles is impressed on a reactor, the 

 iron loss is 248 watts of which 25 per cent, is due to eddy currents. 



i What will be the iron loss when 220 volts at 60 eyries i< 

 impressed on the reactor? (b) What will be the iron loss when 

 110 volts at 30 cycles i< impressed on the reactor? Neglect the 

 resistance drop. 



5. A reactor has two electric circuits having the same number 

 of turn- which may be connected in serif- or in parallel. When 

 they are connected in series across 220-volt, 60-cyele main- the 

 iron loss is 326 watts, of which 89 watts is due to eddy current-. 

 What will be the iron loss if the coils are connected in parallel 

 across the same mains? Neglect the resistance drop. 



6. With 425 volts at 25 cycles impressed on the low-tension 

 winding of a transformer 2500 watts is supplied at no load. If 

 the frequency of this impressed voltage is increased to 40 cycles 



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