. Hawkins electrical guide. Questions, answers & illustrations; a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications; a practical treatise. revolution (cycle) when steam d paad below back pressure (when current and pressure an work (negative watts) be done when steam expands below back pressure (when there is lag), the efficiency (power factor) is (M — S) + M. Wattless Current; Power Factor Zero.—When power factor is zero, it means that the phase difference be:the current and the pressure is 90
. Hawkins electrical guide. Questions, answers & illustrations; a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications; a practical treatise. revolution (cycle) when steam d paad below back pressure (when current and pressure an work (negative watts) be done when steam expands below back pressure (when there is lag), the efficiency (power factor) is (M — S) + M. Wattless Current; Power Factor Zero.—When power factor is zero, it means that the phase difference be:the current and the pressure is 90°. The term rmtHtn current, as understood, does not indicate anabsence of electrical energy in the circuit; its elements a THE POWER FACTOR 1,111 but not in an available form for external work. The false powerdue to the so called wattless current pulsates in and out of thecircuit without accomplishing any useful work. An example of wattless current, showing that the power factor is zerois illustrated in fig. 1,353. Here the angle of lag is 90°, that is, the cur-rent is 90° behind the pressure. The power curve is constructed from the current and pressure curves,and, as shown in the diagram, it lies as much below the zero line. Pig. 1,353.—Example of wattless current showing that the power factor is zero when thephase difference between current and pressure is 90°. For zero power factor the currentmay lead 90° as in fig. 1,352, or lag 90° as here shown. Since the shaded or negative areas =the plus areas, the average power (indicated by WW which coincides with the zero line)is zero, that is the circuit is carrying current under pressure yet delivering no power,hence, the power factor is zero. as above, that is, the two plus power areas which occur during eachperiod are equal to the two negative (shaded) power areas, showingthat the circuit returns as much energy as is sent Out. Hence, the totalwork done during each period is zero, indicating that although a currentbe f
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