Power factor corrected input

Power factor correction circuits are intended to increase the conduction angle of the rectifiers and to make the ac input current waveform sinusoidal and in phase with the voltage waveform. The input waveforms can be seen in Figure C-2. This means that all the power drawn from the power line is real power and not reactive. The net result is that the peak and RMS current drawn from the line is much lower than that drawn by the capacitive input Alter circuit traditionally used. 

Active power factor correction circuits can take the form of nontransformer isolated switching power supply topologies, such as buck, boost, and buck/boost. The buck topology in Figure C-3 produces an output dc voltage lower than found at its input, whenever the PFC stage is operating (F > Fom). In other... 

C.1 A Universal Input, 180W, Active Power Factor Correction Circuit... 

Recently there has been growing interest in power factor correction circuitry. Power factor, which is defined as the ratio of the apparent required power to the actual true power, ultimately affects the circuit s efficiency, thus varying the cost of electricity. It seems that almost all AC-powered equipment now require some form of active power factor correction in order to operate efficiently. Active power factor correction utilizes electronics to force the input current to look like a... 

FIGURE 3.19 Transient due to motor starting. The motor had an input capacitor for power factor correction, and the motor and capacitor were turned on simultaneously. 

In a typical off-line input stage, with no Power Factor Correction ( PFC ) stage present, the input bridge conducts only for part of every ac half-cycle as seen from Figure 13-1. 

For a given tank size, the ultimate design objective is the relation between power input and impeller size at a specified uniformity. The factors governing such information are the slurry volume, the slurry level, and the required uniformity. The method of Oldshue has corrections for these factors, as F Fz, and F3. When multiplied together, they make up the factor bA which is the ordinate of Figure 10.8(d) and which determines what combinations... 

In the internal representation model the time-frequency plane is divided in cells with a resolution of 20 ms along in the time axis (time index m) and of 0.2 Bark along the frequency axis (frequency index /). A first approach was to use the power ratio between the output y and input x, py px in every (At, A f) cell (m, /) as a correction factor for the noise disturbance L (m, l) in that cell (nomenclature is chosen to be consistent with [Beerends and Stemerdink, 1992]). 

Determine the required correction factors. A centrifugal pump handling a viscous liquid usually must develop a greater capacity and head, and it requires a larger power input than the same pump... 

Compute the fan speed and power input. Multiply the capacity-table r/min and bhp by the composite correction factor to determine the actual r/min and bhp. Thus, using data from Table 6.31, the actual r/min is (1096)(1.1147) = 1221.7 r/min. Actual bhp is (99.08)(1.1147) = 110.5 hp. This is the horsepower input required to drive the fan and is close to the 113.2 hp computed in the previous example. The actual motor horsepower would be the same in each case because a standard-size motor... 

Figure 9.24 shows that for a typical 1-hp/lOOO-gal (0.2 kW/m ) power input, the blend time would go up from about 0.1 min in a 1-gal reactor to 0.8 min in a 10,000-gal reactor. Would this type of increase have any detrimental effect on the reaction system Of course the answer depends on the specific chemistry. Comparative mixing times are given for different impellers. These are shown in the following equation for the correction factor, CF. If the mix time is known for a given impeller system, multiplying this time by the CF gives the mix time for a different system ... 

With Cj = 10 and = 1.5, Tj = 0.76 at 15 to 20 C. Disregarding the two other parameters, the corrected amount of oxygen becomes 2 358 kg day b. Correction factor F related to the shape of the aeration tank and to hydraulic conditions. Depending on the type of surface aerator and the shape of the tank, the second F fector 12 = Fi can be calculated (shape of the tank) x F2 (ratio between width and depth) x F3 (specific stirring power) char can be 0.9 for example. A nominal net specific aerator input measured at the shaft of 2 kg kWh of O2 becomes a real input of 1.8. Four aerators, with 20 kW of absorbed power, therefore supply 4 x 20 x 1.8= 144 leg of O2 per hour for a total of 74 that are required on the average. They can be run intermittently and still ensure a maximum stirring power of 37 W m of tank. 

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