Total impedance

The external resistance adds up to the total impedance of the motor windings and limits the starting current. It also improves the starting power factor. 

Then the total impedance through the ground circuit 20.4.2 Impedance neutral grounding system... 

A.c. impedance. Measurements of the frequency variation of impedance allow separation of the change transfer resistance from the contributions to the total impedance of the environment resistance, surface films, adsorbed layers, etc. Robust instruments utilising a two-frequency technique have been developed . 

Impedance Some of the errors arising from the use of linear polarisation resistance led to interest and development in a.c. systems.An early development used a fixed a.c. frequency and a commercial instrument was produced in the UK. Inaccuracies still occurred, however, and were due to the electrode impedance which is fequency dependent. Electrode reactions have a capacitance component, in addition to resistance, resulting in a requirement to measure the impedance. However, the total impedance comprises values for the reaction, solution, diffusion and capacitance. Measurements at different frequency are more reliable, particularly where high solution resistances occur. Simplifications for industrial monitoring have been developed consisting of two measurements, i.e. at a high (10 kHz) and low frequency (0-1 Hz). The high-frequency measurement can identify the... 

Typically, the frequency lu of the modulation is varied over a considerable range, and an impedance spectrum Z(lS) recorded. Various electrode processes make different contributions to the total impedance. In many cases it is useful to draw an equivalent circuit consisting of... 

FIGURE 2.27 Change of total impedance spectra for an electrolyte-supported cell when it was poisoned by 10 ppm H2S under (a) different constant current densities, and (b) different constant cell voltage. (From Cheng, Z. et al., J. Power Sources, 172 688-693, 2007. Copyright by Elsevier, reproduced with permission.)... 

Then using Ohm s law, where V = 1Z, the total impedance exhibited in the coil is given as ... 

The total impedance of the coil will also have an often negligible term called the capacitance [Bray and Stanley, 1997]. The capacitance reactance of the coil, Xc is given by ... 

The total resistance of several resistors placed in series (Figure 8.11(a)) is simply the sum of the individual resistances. Similarly, the total impedance of a... 

Worked Example 8.5. Three pure resistors are joined together in series. What is the total impedance if R = 10, R2 = 210 and / 3 = 3.1 fi ... 

The impedances of a cell s leads, contacts and electrolyte solution can be approximated to a situation of impedances in series. Typical values will be Zieads — 1, Zcontacts — 6 and ZQi t).Qiyt0 solution 40 (with all Z values beinq cited at fixed frequency). Calculate the total impedance of these three components when combined together. 

The total impedance of a circuit comprising impedances placed in parallel is obtained by taking reciprocals, as follows ... 

An electrode bears a layer of indium-tin oxide (ITO) having an impedance of 25 Q, on which is a layer of adsorbed chromophore having an impedance of 1.0 (all values of Z being cited at fixed frequency). In addition, between the chromophore layer and the bulk electrolyte is the Helmholtz double-layer (see Section 5.1.2), which has an impedance of 120 By assuming that these three layers act as impedances in parallel, calculate the total impedance, Ziotai-... 

Figure 15. Faradaic impedance (Zp) of porous Pt electrodes on single-crystal zirconia in oxygen at zero bias, as determined from the total impedance (Z) using the methods of Berthier et aLF gQO and (b) 900 X. (c) Model...

Figure 34. Total impedance (2) and faradaic impedance (Zf) of unsintered porous LSM on YSZ measured in air at 850 °C. Electrolyte resistance (i ) has been subtracted from the total impedance, while both i e and the double-layer capacitance (Cdi) have been subtracted from Zp. (Reprinted with permission from ref 215. Copyright 1998 Elsevier.)...

In the case of a simple system considered throughout Sect. 2, it is already clear that both the faradaic charge transfer and the non-faradaic double-layer charging will contribute to the impedance of the electrode-solution interface. In addition to this, we have to account for the ohmic resistances between the connections to indicator and counter electrodes. This was already illustrated in Sect. 1.1, Fig. 1. The first conclusion is therefore that the total impedance can be written as the summation... 

From the transmitter sensitivity, for a true pressure differential of 5 kN/m2, the transmitter output current iT is 5 mA. Neglecting any resistance in the cables connecting the transmitter and the recorder, the total impedance of the circuit is ... 

P, and T, are the pressure and temperature at one end and P2 and T2 refer to the other end, M is the molecular weight of the gas, R is the gas constant, and N is Avogardo s number. This equation applies in the above-mentioned (molecular flow) region, which commences at about 10 J torr. Of particular importance is the direct proportionality of the flow to the cube of the tube diameter. Thus, large-diameter tubing and large-bore stopcocks improve the pumping speed at low pressures. As with a series electrical circuit, the total impedance (proportional to 1 /q) is equal to the sum of the individual impedances, Eq. (2). 

Equations 2.37-2.40 result in the commonly used presentation of the impedance, e.g. the Nyquist and the Bode plots. The first one shows the total impedance vector point for different values of co. The plane of this figure is a complex plane, as shown in the previous section. Electrochemical-related processes and effects result in resistive and capacitive behaviour, so it is common to present the impedance as ... 

The resistance of the electrolyte, Ra, represents the ohmic resistance of the complete column of electrolyte between both electrodes. Note that in this way of presentation, the Faradaic impedance cannot necessarily be correlated with an occurring process, therefore it is represented by a general symbol ZF. It can be seen in this case that the total impedance consists of contributions from the working and the counter/reference electrodes, and knowledge of the behaviour of only the working electrode needs manipulation. A simple possibility is to use a CE/RE electrode with much larger surface than the WE. However, in the work presented in this book, this manipulation is not done, because the system used here will be used in applications as a set of two identical electrodes. In addition, one of the parameters that we are interested in is the electrolyte resistance, a parameter that is suppressed when using electrodes of different surface areas. 

Considering PSD or PLD, the total impedance of the pores, Ztot is given by... 

The faradaic impedance, Zf, and the total impedance how to calculate Zf from experimental measurements... 

Hong et al. examined the effect of nitric acid passivation on type 430 ferritic stainless steel using potentiodynamic polarization, EIS, and Auger electron spectroscopy (AES) (18). Passivation treatments were carried out on wet polished surfaces by immersion for 60 minutes in nitric acid solutions ranging from 1 to 61% at 50°C. Pitting potential and the magnitude of the total impedance were positively correlated with surface Cr concentration. In response to this study,... 

Figure 3.6. Complex plane graph of the total impedance at low frequencies 3.3.2.2 High-Frequency Limit...

This result is presented in Figure 3.7, where the origin of Zre is the double-layer capacitor Cd. When co —> °°, the contribution of Cd to the total impedance is close to zero. Therefore, the total impedance becomes Reh as presented by the left intersection of the semicircle and the real axis. As m decreases, Zre increases. When co further decreases, Cd becomes very large, resulting in a total impedance of Rei + Rct, as presented by the right intersection of the semicircle and the real axis. If co decreases to an extremely low value, i.e., co —> 0. the plot becomes the 45° straight line as described in Figure 3.6. 

From Equations 3.102 and 3.103, the real and imaginary parts of the total impedance can be calculated ... 

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