Variable voltage power supply

The apparatus shown in Fig. 2 has a 500-mL reaction vessel, which is coimected to a 50-mL reservoir for liquid /BP via a stopcock and a standard-taper joint, t The coimecting tubing between the reaction vessel and the mercury in the manometer must be wrapped with commercial heating tape or wound carefully with heating wire. The temperature of this section, which should be as short and of as small bore as feasible, is controlled with a variable-voltage power supply. It is not necessaiy to control this temperature accurately, but it should be close to the bath temperature (say, within 20°C) and must be above the boiling point of acetone (56°C). 

The cell is connected to a variable-voltage power supply.10 A voltage of 1.00 V dc is applied. Initially, fuzzy, bronze-colored, needlelike crystals form longer crystals form in a 2-4 week period. The crystals are collected by suction filtration through a medium-porosity fritted glass filter. The crystals are washed with four 1 -mL portions of ice-cold (0°) water and allowed to dry in the air on filter paper. The checkers of this synthesis obtained a 62% yield via the electrolytic method. Larger crystals can be prepared by using one-half the concentration of Pt as stated in the electrolytic method. In this case, no white precipitate forms, however, a smaller yield is obtained. 

Variable voltage power supplies are nice to have around either to power some trial circuits, to substitute for a malfunctioning power supply, or to supply a variable voltage for testing, for example, an ADC. 

The recirculation system is based on the use of internal glandless pumps driven by wet, asynchronous motors, supplied individually with "variable frequency - variable voltage" power from frequency converters. This type of pumps has been operating reliably (for more than three million operating hours) since 1978. Within a couple of years such internal pumps will be in use also by other BWR vendors, in the ABWR plants. 

Incoming three-phase AC power is rectified and smoothed to generate a variable voltage DC supply. This DC voltage is then switched among the three output phases to generate a step waveform that approximates a sinusoidal waveform. The switching is done by six SCRs (silicon-controlled rectifiers), which are sequentially fired at the proper frequency by a solid-state circuit. 

A standard wattmeter method was used to measure the total core loss. In this method, an important experimental difficulty may arise immediately if an ordinary variable-frequency power supply is used for measurement near or above saturation, distortion of both voltage and current wave forms will result, and the measured loss may depend as much on the impedance of the supply as on the magnetic core. In fact, if both waves are considered expanded in Fourier series, the measured power will contain components at a number of frequencies, so that it will be impossible to state the power loss as existing at one frequency nor obtain a reasonable value of hysteresis loss by extrapolation to zero frequency. 

Power Supplie.s Iligh-voltage ac and dc power supplies for electrostatic separators are iisiiallv of solid-state construction and feature variable outputs ranging from 0 to 30,()()() for ac wiper transformers to 0 to 60,000 for the dc supply The maximum current requirement is approximately 1,0 to 1,5 rnA/rn of electrode length. Powder supplies for industrial separators are typically oil-insulated, but smaller diw-epoxv-insulated supplies are also available. 

Quasi-resonant converters are a separate class of switching power supplies that tune the ac power waveforms to reduce or eliminate the switching loss within the supply. This is done by placing resonant tank circuits within the ac current paths to create pseudo-sinusoidal voltage or current waveforms. Because the tank circuits have one resonant frequency, the method of control needs to be modified to a variable frequency control where the resonant period is fixed and the control varies the period of the non-resonant period. The quasi-resonant converters usually operate in the 300 kHz to 2 MHz frequency range. 

Power supplied to the ozone generators. The parameters measured include amperage, voltage, power, and frequency, if this is a controllable variable. 

If a suitable press is not available, one may improvise as follows The heating plates of two electric irons are first bored to accept a thermocouple and then connected in parallel to the power supply through a variable transformer. A calibration curve is determined for the temperature attained at different voltages. For the preparation of a film the finely powdered polymer is placed, as described... 

Electrochemical calorimetry — is the application of calorimetry to thermally characterize electrochemical systems. It includes several methods to investigate, for instances, thermal effects in batteries and to determine the -> molar electrochemical Peltier heat. Instrumentation for electrochemical calorimetric studies includes a calorimeter to establish the relationship between the amount of heat released or absorbed with other electrochemical variables, while an electrochemical reaction is taking place. Electrochemical calorimeters are usually tailor-made for a specific electrochemical system and must be well suited for a wide range of operation temperatures and the evaluation of the heat generation rate of the process. Electrochemical calorimeter components include a power supply, a device to control charge and discharge processes, ammeter and voltmeter to measure the current and voltage, as well as a computerized data acquisition system [i]. In situ calorimetry also has been developed for voltammetry of immobilized particles [ii,iii]. 

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