Ques. How can the power factor be kept high?
Ans. By carefully designing the motors and other apparatus and even making changes in the field current of motors which are already installed.
Ques. How is the power factor determined in station operation?
Ans. Not by calculation, but by reading a meter which forms one of the switchboard instruments.
Fig. 1,368.—Fleming's combined voltmeter and ammeter method of measuring power in alternating current circuits. It is quite accurate and enables instruments in use to be checked. In the figure, R is a non-inductive resistance connected in shunt to the inductive load. The voltmeter V measures the pressure across the resistance XY. A and A1 are ammeters connected as shown. Then, true watts = (A12 - A2 - (V/R)2) × R / 2. If the volt meter V take an appreciable amount of current, it may be tested as follows: disconnect R and V at Y, and see that A and A1 are alike; then connect R and V at Y again, and disconnect the load. A1 will equal current taken by R and V in parallel.
Ques. When is the power factor meter of importance in station operation, and why?
Ans. When rotary converters are used on alternating current lines for supplying direct currents and the sub-station operators are kept busy adjusting the field rheostat of the rotary to maintain a high power factor and prevent overheating of the alternators during the time of day when there is the maximum demand for current or the peak of the load.