DC power supply

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. 

A bench-top power supply that can simulate the input power source. This will be a large dc power supply with voltage and current ratings in excess of what is needed. For off-line power supplies, use a variac with a current rating in excess of what is needed. 

Baranowsky, P.W., A.M, Kolaczkowski, and M.A. Fedele, A Probabilistic Safety Analysis of DC Power Supply Requirements for Nuclear Power Plants, April 1981. 

Direct current motors are most appropriately used in applications where a dc power supply is available or where a simple method of speed control is desired. The fans used in automobile heating and air conditioning systems are driven by direct-current motors. 

The probes are 1-mm nickel rods with square ends. They are powered by 100-V dc power supplies. The positive side of the power supply is connected to the cell body. (This makes the probes cathodic to the case.) The control modules have 12 M3 resistance so that when contact is made, less than 10 mA flows through the circuit this is not a dangerous current. (The use of a 12-V power supply and lower resistance modules did not reliably deliver a control signal when contact was made this may have been caused by the buildup of a passive film on the probe that was not cleared by the lower voltage.)... 

A DC power supply with an operating range of 0-60 V was used to supply power to the chip aluminum resistor (2). The Teflon module cartridge was placed under-... 

An ESRI system can be built with small modifications of commercial spectrometers by, for example, gradient coils fixed on the poles of the spectrometer magnet, regulated direct current (DC) power supplies, and required computer connections [40,53,55]. Gradients can be applied in the three spatial dimensions, and a spectral dimension can be added by the method of stepped gradients. The spectral dimension is important when the spatial variation of ESR line shapes (as a function of sample depth) is of interest this situation will be described below, in the ESRI studies of heterophasic polymers. In most systems, the software for image reconstruction in ESRI experiments must be developed in-house. 

One of the hardest to analyze and fix are probably the chain reaction problems. For example, in an AC-DC power supply, we know all too well that the switch can blow... 

For example, in Figure 3-7, we have a typical AC-DC power supply (Flyback or Forward). The threshold voltage of such a high-voltage Fet is typically high (around 8V). It is common to try to achieve fast turnoff but relatively slower turn-on. The concern is that if... 

In this particular chapter, we will focus a great deal on ceramic capacitors since these have become extremely popular today. However, in commercial AC-DC power supplies, the aluminum electrolytic (or elko) is still king, so we will talk about that component too. Unfortunately, we will have to pretend none of the others even exist. We just don t have the space for all of them here. 

When making commercial AC-DC power supplies, you will find that large electrolytic capacitors and also transformers and inductors can easily tear off the board in any standard... 

On a typical one-sided board (still very common in commercial AC-DC power supplies), as the number of capacitors you try to parallel goes up, so does the intervening PCB trace impedance. Take, for example, Figure 5-1, where we have the simple case of one output capacitor. A small advisory here—if you try to reduce the impedance further by making the current loop smaller and smaller, the capacitor would eventually start comparing notes with the heatsink on the topic of temperature, and that can t be good for its life expectancy. 

Let us take the popular 384x family for the purpose of illustrating some key routing principles in AC-DC power supplies. 

In general, most converters are tested on the bench with the electronic load set to constant current (CC mode). True, that s not benign, nor as malignant as it gets. But the implied expectation is that converters should at least work in CC mode. They should, in particular, have no startup issues with this type of load profile. But even that may not be the end of the story Some loads can also vary with time. For example, an incandescent bulb has a resistive profile, but its cold resistance is much lower than its hot resistance. That s why most bulbs fail towards the end of their natural lifetime just when you throw the wall switch to its ON position. And if the converter is powering a system board characterized by sudden variations in its instantaneous supply current demand, that can cause severe problems to the converter, too. The best known example of this is an AC-DC power supply inside a computer. The 12V rail goes to the hard disk, which can suddenly demand very high currents as it spins up, and then lapse back equally suddenly into a lower current mode. 

Once you have a stable clock, you might like to check the jitter. So how much jitter is acceptable In an AC-DC power supply with no PFC correction, especially at low line, the input voltage ripple is quite high. As this instantaneous input voltage moves up and down, a... 

Now, where could the problem lie Is it within the power supply stage itself, or is it external If you have peeled the onion as I suggested previously, you are hopefully sure the efficiency is not being lost within the EMI filter of your AC-DC power supply. Bypass or disconnect everything external and confirm you have a problem. 

Figure 11-1 One Possible Way of Conducting a Noise and Ripple Measurement for an AC-DC Power Supply... 

Figure 5.11. Electrolysis circuit layout. 1, 2 Sample and washing solution compartments. 3 Three-way stopcock. 4 Ammeter. 5 500 V Variable dc power supply. 6 Crucible. Source [395]... 

The ellipsometer used in this study is described elsewhere(3). It consists of a Xenon light source, a monochromator, a polarizer, a sample holder, a rotating analyzer and a photomultiplier detector (Figure 1). An electrochemical cell with two windows is mounted at the center. The windows, being 120° apart, provide a 60° angle of incidence for the ellipsometer. A copper substrate and a platinum electrode function as anode and cathode respectively. Both are connected to a DC power supply. The system is automated with a personal computer to collect all experimental data during the deposition. Data analysis is carried out by a Fortran program run on a personal computer. 

Figure 1 A schematic diagram of the experimental set-up consisting of a rotating analyzer ellipsometer, an electrochemical cell with a copper substrate and a platinum electrode connected to a DC power supply. 

Traditional electrophoresis paper, cellulose acetate or polymeric gels used as a supporting medium for the electrolyte solution enclosed tank with electrodes and buffer reservoirs dc power supply. 

The illuminator must have a stabilized DC power supply, otherwise fluctuations in intensity will appear in the signal from the photometer. 

Commercially available combustible gas detection systems generally use 24 VDC as the power supply for field devices. 24 VDC is inherently safer and corresponds the voltages increasing used by most instrument systems in process areas. A main supply voltage converter can be used to step down or convert from AC to DC power supplies. 

Regulated direct current (DC) power supplies designed for electrophoresis allow control of every electrophoretic mode. Constant voltage, constant current, or constant power conditions can be selected. Many power supplies have timers and some have integrators allowing runs to be automatically terminated after a set time or number of volt-hours (important in IEF). All modes of operation can produce satisfactory results, but for best results and good reproducibility some form of electrical control is important. The choice of which electrical parameter to control is almost a matter of preference. The major limitation is the ability of the chamber to dissipate the heat generated by the electrical current. 

For the electrolyses, a cell and a DC power supply are needed. For a thorough coverage, see again Chapter 2. For most conversions, especially the exploratory ones, the author has used a double-walled beaker-type cell (Fig. 1). 

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