DC Current and Voltage

The DC Sweep is used to find DC voltages and currents in a circuit. 

The DC Sweep can be used to find DC voltages and currents for multiple values of DC sources. It can answer the following question in one simulation What is the voltage at node 1 for VI = 10 VDC, VI = 11 VDC, and VI = 12 VDC This question could be answered using the DC Nodal Analysis if the DC Nodal Analysis were run three times. 

Analog panel meters are available that measure dc voltage and current, ac voltage and current, temperature, motor load, elapsed time, and frequency. Analog meters are preferred where readings are constantly changing or fluctuating. 

Operational amplifier. A linear, high-gain DC voltage or current amplifier with high input impedance, low output impedance, and the capability of producing a bipolar output from a bipolar input. 

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. 

The DC filter choke is used for ripple voltage and current reduction on the output of the switching power supply immediately following the existing filters. It is also used as an EMI filter on switching power supplies that have a single power line on the input, such as battery and distributed power systems. 

For current-controlled conversions, a current-regulated DC source (up to 50V and 2A, with voltage and current display) [175] or one or two car batteries (12 to 24V) with a volt and ampere meter [176] or a regulated AC power source with a rectifier are sufficient as the power supply. 

The first report of an all-SiC, three-phase dc-ac inverter was presented by Seshadri et al. [17] in 1999. Although Seshadri s inverter used SiG GTOs and p-/-n diodes, it was operated at ambient temperature and at voltage and current levels so low that the authors were unable to ...determine typical switching characteristics of the individual SiG components. From the standpoint of technology development, there exists a need to evaluate SiC technology under relevant circuit stresses. 

Fig. 5.8 Schematic diagram of polarographic (or voltammetric) circuits for two-electrode (a) and three-electrode (b) systems. WE(DME) indicator or working electrode (dropping mercury electrode in the case of polarography) RE reference electrode CE counter electrode DC voltage (V) DC voltage source Current (/) current measuring device.

Figure 13.10 The change of (a) voltage and current, and (b) the current density with DC power input in TMS glow discharge 1 seem TMS, 5 panels, 6-cm panel spacing.

Figure 13.12 The influence of panel numbers on (a) the plasma voltage and current, as well as (b) the current density and TMS deposition rate on the cathode (the panels) TMS, 1 seem, 50 mtorr, DC 5 W, 6-cm panel spacing.

The DC-DC converter changes the electric characteristics of voltage and current supplied by the electric source in order to feed the electric machine and satisfy the load mechanic requirements. 

AC electric drives require more sophisticated converters when they are supplied with DC sources, because electric machines requires periodic voltage and current waves with a variable frequency depending on the load requirements. In Fig. 5.8, the scheme of an example of three-phase induction motor driven by a pulse-width-modulated inverter is reported. In this scheme a three-phase bridge connection with six power modules is shown to form the so-called inverter. Each power module can be composed by a number of power switches connected in parallel to carry higher currents. Across each power switch (IGBT) a parallel diode is connected to provide a return path for the phase current when the power module is switched off. 

Downstream of the converter, a DC bus connects this device in electric parallel with the battery pack to supply the electric drive. Voltage and current sensors are installed on batteries and upstream-downstream the DC-DC converter, as shown in Fig. 6.2, to monitor the electric energy flows between the different components of the propulsion system. The DC-DC converter allows the stack output power to be varied according to the selected control strategy. Furthermore, some security switches are adopted, in order to instantaneously disconnect the electric load from battery pack and/or stack. An I/O laboratory board is used for data acquisition and setting of the electrical parameter affecting the DC-DC converter behavior. 

For the simplest machining strategies a DC power supply is enough. However, the supply should be able to provide voltages and currents that are high... 

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