CHAPTER X 

 TRANSFORMER DIAGRAMS AND REGULATION 



Note. Scak all quantities asked for. If problem V-22 has not 

 been taken, include here. " Magnetizing current" is taken as the 

 magnetizing or wattless component of the exciting or no-load 

 current. The angle as well as the length of vector is required. 

 In all problems unless otherwise stated or implied the mean length 

 of turn and the current density in the two windings will be taken 

 as the same. Note also that to adapt the problems to easy 

 graphical solution the impedance drop, magnetizing current and 

 iron losses have been exaggerated as compared with those usually 

 found in commercial transformers. 



1. A transformer has 600 primary and 60 secondary turns; 

 120 magnetizing ampere-turns are necessary; draw the ampere- 

 turn diagrams for currents of 0, 10 and 20 amperes, secondary 

 non-inductive load, and find the primary currents and lags. (See 

 note above.) (7 min.) 



2. Draw the same loads both lagging and leading the e.m.f. by 

 30 degrees, and find the primary currents and lags. (10 win.) 



3. A 5 to 1 transformer with 80 secondary turns, takes 120 

 magnetizing ampere-turns; what are the primary currents and 

 power factors for 0, 4 and 8 amperes, non-inductive load? (8 min.) 



4. A 5 to 1 transformer has a secondary e.m.f. of 2200, a mag- 

 netizing current in phase with the flux of 2, and losses of 5 kilo- 

 watts; draw diagrams for loads of 60 amperes, both when lagging 

 and when leading 30 degrees, and find the primary e.m.f., currents 

 and power factors. (See note above.) (13 min.) 



5. Same as problem 4, except that the coils have resistances of 

 52 and 1.8. Find also the full-load transformation ratio. Refer 

 the phase angles to the induced e.m.f. (25 min.) 



6. A 10 to 1 transformer with 220-volts secondary induced 

 e.m.f. and a load of 400 amperes has 1.1 kw. iron losses and a 

 magnetizing current of 2 amperes; draw and scale diagrams for 

 secondary power factors of 80% and 40%, and find the primary 

 currents. (15 min.) 



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