6 
ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
300. By means of Equation 26 of the Instruction Book, calculate 
the leakage factor of this synchronous motor and see 
whether the value thus obtained is in accordancé iene that 
assumed above. 
301. Calculate 4 points of the no-load characteristic, for 1,000, 
~ 1,800, 2,200 and 2,500 volts and collect: the different data 
in tabular form, similar to Table 19 of the Instruction 
Book. The path lengths which must be known for this 
purpose are to be taken from a full-sized sketch or may be, 
calculated. 
_ 302. By means of Equation 29 of the Instruction Book, calculate 
the short circuit constant for this synchronous motor, 
determining first the reluctance of the armature leakage 
path. For this purpose take the projecting-out part of the 
armature winding as 27, —9 inches. 
303. The short circuit constant being calculated as ad) 16, deter- 
mine by means of Equation 15 of the Instruction Book the, 
amount of field ampere turns per pole which correspond to 
the normal shortcircuit current of the armature. 
304. Plot the no-load and short circuit characteristics of this 
synchronous motor, applying the following scales: — > 
1,000 ampere turns per pole ='1 inch. 
500 volts terminal pressure = 1 inch. 
50 amperes short circuit current = aS inch, 
305. In the same figure determine graphically the V-characienae 
and therefrom state the necessary’ ‘amount of excitation 
ampere turns corresponding to the normal armature current 
of 61.8 amperes with a leading power factor of cos. p=, .90 
306. Assuming a total winding depth of 1.4 inch and a thickness of 
about .25 inch for the metal bobbin together with its in- 
sulation on each side of the pole core, calculate as a first 
approximation the length of a mean turn of the field coils. 
307. Taking into consideration a margin of about 10% in éxcitation, 
calculate for 255 volts excitation pressure the ‘necessary 
