ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
268. 
269. 
270. 
2% L. 
272. 
What should be the maximum load capacity of a synchron- 
ous motor driving a continuous, current dynamo for 
accumulator chafing? mee 8 5 Se Dake S 
Give the approximate maximum load Spats of the two 
phase synchronous ‘motor referred to in Question 264, 
when the short circuit current for normal excitation is 
163.6 amperes. 
What are the two necessary characteristics for determining 
the excitation current for different pow er factors ? ? 
What form should the V-char acteristic have with prin bi 
the steady running of a synchronous motor ? 
Define the efficiency of a synchronous motor and state the 
formula for same. 
Calculate the half load efficiency of the 450 HP. eyineleone 
ous motor, for which the different losses are indicated in 
Fig. 95 of the Instruction Book. The power factor being 
assumed equal to cos pg = 1. 
DESIGN A REVOLVING FIELD TYPE TWO-PHASE SYNCHRONOUS MOTOR 
TO THE FOLLOWING SPECIFICATION, 
Output = 300 HP. 
Speed = 240 Revs. 
Frequency = 40 cycles. 
Terminal pressure = 2200 volts. 
Connection: Two independent circuits. 
This motor to be capable of carrying a leading current of cos p 
= .90 at full load. 
The efficiency shall not be below 91.5% for the specified working 
conditions. 
The temperature rise on any part of the machine shall not ex- 
ceed 75 degrees Fahrenheit. 
The momentary overload capacity shall be about, 2.25 the 
normal capacity, the motor being normally excited. 
For the armature the long coil type in open slots is to be applied, 
and the armature core is to be made up of .02 inch laminae, 
whilst for the poles .04 inch laminae are to be applied. 
