Initial condition capacitor

It is important to note that when PSpice calculates the bias to determine the initial condition of the capacitor, it sets the voltage of the pulsed source to its initial voltage. For our pulsed waveform, PSpice will calculate the initial capacitor voltage assuming that Vin = 5 V. This will cause the integrator to saturate initially. To prevent saturation, we must set the initial condition of the capacitor to 0 V. See Section 6.B, pages 333-337, for details on setting the capacitor initial condition. 

In this section we will observe the transient response of a capacitor circuit with an initial condition. We will use the circuit below ... 

Notice the plus (+) sign on the capacitor. This plus sign indicates the positive voltage side of the capacitor for initial conditions. Make sure the plus sign is oriented as shown in the schematic. We would like the capacitor to have an initial condition of 5 V, and we would like the switch to close at t = 1 ms. The initial condition of the capacitor is not one of the displayed attributes, so we must edit all the attributes of the capacitor. Double-click the LEFT mouse button on the capacitor graphic, to obtain the spreadsheet for Cf ... 

Note that the initial condition of the capacitor is 5 (5 volts) and the switch closes at time equals fill (1 millisecond). The next thing we need to do is set up the Transient Analysis. Select PSpice and then New Simulation Profile ... 

S0LUTI0I1 The initial condition of the capacitor does not need to be specified because PSpice will determine the initial conditions from the circuit. The part name for the normally closed switch is N/C switch. 

Instead of specifying an initial condition on the capacitor, the initial voltages of nodes can be specified using the parts IC1 and IC2. For the circuit of Section 6.B, we will use the part IC1 to specify the initial condition of the capacitor. Get a part called IC1 and place it in your circuit ... 

Note that we did not specify initial conditions. When you do not specify initial conditions, PSpice will determine them itself. PSpice will determine the initial conditions from the state of the circuit at t = 0. In this case, the voltage of the PWL source is zero at t = 0. The initial conditions Will be determined with this source set to zero. Since this is the only source in the circuit, all sources are zero at t = 0, so the initial condition of the capacitor must be zero at t = 0. 

In this section we will demonstrate the transient response of an inductor circuit with a switch that is normally closed. The initial condition of the inductor will not be specified by an IC= line in the circuit. Instead, the initial condition will be determined by PSpice from the initial state of the circuit before the switch changes position. If you wish to specify the initial condition of the inductor, it is specified in the same way as the initial condition of a capacitor. For an inductor, the direction for positive current is into the dotted terminal, as shown in Figure 6.1. The dot is always shown on the inductor graphic. The graphic should be rotated to obtain the desired direction of positive current flow. 

S0UIT1DI1 Wire the circuit as shown. A 1 kHz clock is used. Use the capacitor startup circuit on page 495 to preset the first flip-flop to 1 and the remaining flip-flops to 0. Note that the initial condition of the capacitor is set to zero. 

Add UIC (Use Initial Conditions) to the. TRAN statement. This statement causes SPICE to bypass the DC operating point analysis. Initial conditions should be placed on capacitors at their expected operating voltage. Just as with the use of incorrect nodesets, incorrect initial condition values can produce incorrect solutions or nonconvergence. Results should be verified for validity. 

To allow this circuit to converge, the ABSTOL setting in the OPTIONS line was modified from lp (default) to 1U. This was required on all three simulation programs. The UIC statement was also used on the. TRAN line. Initial conditions were set on the output capacitors (60 V on each). 

Integration of Eq. (4.93) with the initial condition of an empty capacitor, Q(0) = 0, yields... 

If a capacitor with its maximum possible charge is discharged and the initial condition Q(0) = Qo is used (for simplicity s sake time is newly counted from t = 0), the discharge process is described by... 

Rapid reinsertion of the capacitors as soon as the fault coiiditions are removed is an important requirement to retain the stability of the system. This can be achieved with the use of an additional ZnO. non-linear resistance (ZnO being the latest in this field compared to SiC. which was used earlier), across the capacitor banks (Figure 26.12). Generally, the ZnO resistor will be adequate to dampen the fault current without initiating the spark gap. and w ill limit the overvoltage across the capacitors. It will also permit automatic reinsertion of the capacitors as soon as the fault conditions are removed without causing a delay. The spark gap will serve as a backup to the ZnO resistor in the event of very severe faults. 

This capacitor experiences the same current waveform at the power switch, which is a trapezoid with an initial current of about 1A rising to 2.8 A with very sharp edges. This capacitor has much more rigorous operating conditions than the output filter capacitor. I will estimate the RMS value of the trapezoidal current waveform as a piecewise superposition of two waveforms, a rectangular 1A peak waveform and a triangular waveform with a 1.8 A peak. This yields an estimated RMS value of 1.1 A. The value of the capacitor is then calculated as ... 

The uniformity of tantalum powder is also a veiy important parameter of capacitor-grade tantalum powder. The loss of powder uniformity can initiate during the regular reduction process due to varying conditions at the beginning and end of the reduction process. At the end of the process, the concentration of tantalum in the melt is very low, while the sodium content increases. Based on the complex structure model of melts, it should be noted that the desired particle size of the powder is formed at the veiy beginning of the process, while the very fine fraction forms at the end of the process, independent of the initial content of the melt. The use of special equipment enables to perform a continuous reduction process with simultaneous loading of K TaFy and sodium, which can influence the improved uniformity of the primary powder [592,603,604],... 

Pore formation is a common feature of many metal and semiconductor electrodes under anodic conditions in various electrolytes. Common products, for example aluminum capacitors, have been manufactured for decades using electrochemical pore formation techniques. Nevertheless in many cases the physics of pore initiation and propagation is poorly understood. 

For very rapid reactions such as the ionization of H2O, it is difficult to determine the rate constants using conventional methods. One often-used method is the relaxation method. The system is initially at equilibrium under a given set of conditions. The conditions are then suddenly changed so that the system is no longer at equilibrium. The system then relaxes to a new equilibrium state. The speed of relaxation is measured, usually by spectrophotometry, and the rate constants can be obtained. One technique to change the conditions is to increase temperature suddenly by the rapid discharge from a capacitor. This technique is called temperature-jump technique. 

In Figure 1-11 the current escalates initially, but then after several cycles, automatically levels out, in what is clearly a steady state. That is because every cycle the capacitor charges up, it progressively increases the slope of the down-ramp, eventually allowing the converter to settle down naturally into the basic condition AIon = AIoff = AI. And once that is achieved, it is self-sustaining ... 

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