DIRECT-CURRENT DYNAMOS AND MOTORS. 39 
364. State the usual limits of the electrical efficiency of modern 
machines. 
365. Define the intake and output of dynamo-electric ma- 
chines. : 
366. Give the general formula for the commercial efficiency of 
a generator. 
367. Give the general formula for the commercial efficiency of 
a motor. 
368. Give the formula for the commercial efficiency of a com- 
pound wound generator. 
369. Give the formula for the commercial efficiency of a 
- shunt-wound motor. 
370. By means of Table 29, Instruction Book, find the ap- 
proximate power-loss by friction in a 35 K.W. dynamo. 
371. Between what limits does the commercial efficiency of 
modern machines usually range? 
372. Upon what does the commercial efficiency of a dynamo 
depend? 
373. Give formula for the commercial efficiency of a belt- 
driven generator, if the data for computing the me- 
chanical power transmitted by its belt are known. 
374. State the average percentage of power loss in a horizontal 
dynamo belt. 
375. How is the gross efficiency of a dynamo-electric machine 
obtained ? 
376. Give the practical limits of the gross efficiency of modern 
dynamos. 
37%. Define the weight-efficiency of a dynamo. 
378. What does a high weight-efficiency indicate? 
379. Give the usual limits of the weight-efficiency for low, 
medium, and high-speed dynamos, respectively. 
