TRANSFORMER DIAGRAMS AND REGULATION 85 



7. If in problem 6 the resistances are 4.8 and 0.04, find the 

 primary currents and power factors, and the terminal voltages. 

 (30 min.) 



8. Draw the three sine curves for the primary, secondary and 

 magnetizing ampere-turns of problem 1, with 20 amperes in the 

 secondary. (25 min.) 



9. Repeat problem 8, with the lagging current of problem 2. 

 (25 min.) 



10. A 5 to 1 transformer has a primary induced e.m.f. of 1200 

 volts, the resistances are 3.1 and 0.13 ohms, the magnetizing current 

 3.4 amperes and the iron losses 660 watts; draw the diagrams for 

 a non-inductive load of 100 amperes, and with the same load 

 lagging 30 degrees behind the induced e.m.f.; find the terminal 

 e.m.f. 's and primary currents. (20 min.) 



11. If in problem 10 the leakage reactances are 6.2 and 0.26 

 ohms, draw the diagrams there called for, and find the primary 

 currents and the transformation ratios. (30 min.) 



12. The secondary current is 10 amperes lagging 30 degrees 

 behind the terminal e.m.f. The induced e.m.f. is 100 volts, the 

 secondary resistance 1 ohm, and its equivalent reactance 2 ohms. 

 Draw the diagram and determine the secondary terminal e.m.f. 

 and its lag. (5 min.) 



13. A 2 to 1 transformer, giving 500 volts induced secondary 

 e.m.f., has a magnetizing current of 5 amperes, an iron loss of 1200 

 watts, secondary resistance and reactance of 5 and 10 ohms; 

 construct and scale the diagram and determine the primary current 

 and terminal e.m.f. 's for a load having a resistance of 20 and a 

 reactance of 4 ohms. See note, page 84. (25 min.) 



14. For the transformer of problem 13, construct the sine waves 

 of e.m.f. 's actually induced by all flux in the primary and 

 secondary coils, also the curves of resistance drops and of terminal 

 e.m.f. (30 min.) 



15. A transformer has 150 primary and 75 secondary turns, a 

 magnetizing current of ^ and a secondary current of 10. The 

 iron loss is 120 watts. The secondary induced pressure is 100. 

 Required the primary current both when the secondary circuit is 

 non-inductive and when a lag of 30 degrees behind the induced 

 e.m.f. is present; find also the tangent of its lag in each case. 

 (5 min.) 



16. A 3 to 1 transformer has 190 secondary turns. The mag- 



