Output transient response

Distance-Velocity Lag (Dead-Time Element) The dead-time element, commonly called a distance-velocity lag, is often encountered in process systems. For example, if a temperature-measuring element is located downstream from a heat exchanger, a time delay occurs before the heated fluid leaving the exchanger arrives at the temperature measurement point. If some element of a system produces a dead-time of 0 time units, then an input to that unit,/(t), will be reproduced at the output a.s f t — 0). The transfer function for a pure dead-time element is shown in Fig. 8-17, and the transient response of the element is shown in Fig. 8-18. 

In a V/f control generally, only the frequency is varied to obtain the required speed control. Based on this frequency, the switching logistics of the inverter control circuit control the inverter s output voltage using the PWM technique to maintain the same ratio of V/f. A W/control is, however, not suitable at lower speeds. Their application is limited to fan, pump and compressor-type loads only, where speed regulation need not be accurate, and their low-spccd performance or transient response is not critical and they are also not required to operate at very low speeds. They arc primarily used for soft starts and to conserve energy... 

The transient response of DMFC is inherently slower and consequently the performance is worse than that of the hydrogen fuel cell, since the electrochemical oxidation kinetics of methanol are inherently slower due to intermediates formed during methanol oxidation [3]. Since the methanol solution should penetrate a diffusion layer toward the anode catalyst layer for oxidation, it is inevitable for the DMFC to experience the hi mass transport resistance. The carbon dioxide produced as the result of the oxidation reaction of methanol could also partly block the narrow flow path to be more difScult for the methanol to diflhise toward the catalyst. All these resistances and limitations can alter the cell characteristics and the power output when the cell is operated under variable load conditions. Especially when the DMFC stack is considered, the fluid dynamics inside the fuel cell stack is more complicated and so the transient stack performance could be more dependent of the variable load conditions. 

When 2M methanol solution is fed to the stack at a flow rate of 2 ml/min and the stack is operated at a constant voltage output of 3.8V, the transient response of the stack current density is shown in Fig. 3 varying the flow rate of air to the cathode. The stack was maintained at a temperature of 50°C throughout the experiment. As shown in the figure, while the stack current is maintained at the air flow rates higher than 2 L/min, the stack current begins unstable at the slower flow rates. A similar result is shown in Fig. 4 for varying methanol flow rate at an air flow rate of 2 lymin. At a methanol flow rate of 8 ml/min, the current density reaches initially a current density value of about 130 mA/cm and then starts to decrease probably due to medianol crossover. As the methanol flow rate decreases, the stack current density increases slowly until the methanol flow rate reaches 3 ml/min because of the reduced methanol crossover. The current density drops rapidly from the methanol flow rate of 2 ml/min. 

Response time. In the literature, response time is usually specified as the time taken for the electrode to reach > 90% of the output. Typical response times are around 30 sec. A fast response time is critical when one is measuring transient phenomena such as oxygen respiration rates in tissue or suspended cells and dynamic measurements of the volumetric mass transfer coefficient in bioreactors. 

A precarious dilemma results when creating a model that can accurately depict a transient response of the converter as well as the output ripple. The ESR of capacitor C2 is a function of frequency. When simulating the output ripple of the converter, the frequency is essentially constant, approximately 25 kHz. However, when the converter... 

In correlating to the transient response, many difficulties arose. The ESR of C2 determines the magnitude of the transient response, as well as the frequency of the output ripple. Varying the ESR of C2 varies the period of the output ripple in which the transient occurred. A larger magnitude of the transient response corresponds to the transient occurring while the transistor is conducting, which indicates that the simulation results are dependent on when the transient occurs. 

The transient domain model shown in Fig. 4.33 was used to measure output ripple voltage, transient response, gate voltage, and inductor current. This model properly predicts the cycle-by-cycle switching effects of the regulator. 

Figure 4.40 shows the simulated output ripple voltage, while Fig. 4.41 shows the simulated output voltage ripple. The measured transient response is shown in Fig. 4.42, while the simulated transient response is shown in Fig. 4.43. 

The transient response of the amplifier was measured by using a 10 kHz square-wave input with a 50% duty cycle. The breadboard results are shown in Fig. 6.27. The bottom trace is the input square wave, while the top trace is the output result. The Micro-Cap, PSpice, and IsSpice results are shown in Figs. 6.28, 6.29, and 6.30, respectively. 

Let us deal with the transient response method. The transient response method is a method of measuring the characteristics of a system in particular, this method is effective when the dynamic characteristics of the system are investigated. In order to clarify the characteristics of the system, a comparison between the input and the output wave forms is useful. In general, the following three input wave forms have been widely used (Figure 2.1) ... 

Upon administration of the drug, there is absorption into the body. Subsequently, the drug is converted to metabolites and/or is physically eliminated. As a result, the amount of drag in the body at any time is the net transient response to these input and output processes. 

Figure 7 shows a typical result of the procedure explained in the last chapter. The signal used for the system excitation is a step signal SCCm.n,H . and SCC. p..., are the measured input and output signals where SCCin, is in fact the transient response of the measurement system. Taking these two signals, the reactor dynamics of the SCC can easily be determined. 

However, the rate at which the output can be corrected by the power supply (under sudden changes in line and load) is also important — since no physical process is instantaneous either. So the property of any converter to provide quick regulation (correction) under external disturbances is referred to as its loop response. Clearly, the loop response is as before, a combination of its step-load response and its line transient response. ... 

In the case of an anay of band electrodes or interdigitated electrode structures, the width of each single electrode element and the gap between the electrode elements must be considered carefully in the sensor design. Interactions between electrode elements and their effects on the transient response to a potential step perturbation will directly affect the overall sensor output. When an interdigitated electrode structure is used, chemical cross-talk among the reactants and products in both electrode elements (cathode and anode) may occur, which will then influence the sensor output [3], Therefore, the relative location of the sensing elements is also an essential consideration. 

Additional refinements of the model were made by Defares et al. (29) and Grodins and James (30). Defares noted that the blood flow to the central respiratory centers increases monotonically with increases in local pCo2> independent of the cardiac output. Defares incorporated this effect into a model that treated the brain as a compartment separate from the other tissues. The response of this model differed somewhat from Grodins model, and its transient response was in closer agreement with experimental data on C02 inhalation. The main drawback of Defares work was the assumption that the pH of the blood varies passively with pC02. Also, circulation time delays and the effect of arterial po2 were not included. 

A 10-kW natural gas fuel processor will be integrated into the power plant. The processor is capable of starting up and producing fuel cell quality reformate in less than 60 minutes. Furthermore, it is able to transition from minimum power to full power (2 kW to 10 kW) in less than 60 seconds. The reformer is a larger version of the unit used in the 3-kW et stationary plant, which has demonstrated good transient response and low CO output (less than 50 ppm throughout its operating envelope). 

To recapitulate, the frequency response of the amplifier can be obtained by measuring the gain at each frequency or alternatively by measuring the response of the output of the amplifier to a rectangular input pulse and a subsequent Fourier transform. (Clearly, there are other pulse shapes which contain many different frequency components, too, but the square pulse is easy to form and its frequency distribution is well known.) The efficiency of the latter method is due to the multiplexing effect, i.e., the fact that we are not taking the data at one frequency at a time and not due to the Fourier transform itself, and this fact was first demonstrated in NMR by Ernst and Anderson (1966). All the spectral information desired is already contained in the transient response to a pulse and the transform merely allows us to decompose the... 

A follow-up design is given in the GT-MHR (Modular Helium Reactor) (see also section 4.7.2.) with a higher power output of 600 MW(th). A standard plant is planned consisting of four of those units. Helium inlet/outlet temperatures are 485 and 850 °C, respectively. The cycle efficiency is predicted to be 47 % [51]. Follow-on evaluations which need to be done include the study of transient response of plant components to normal and off-normal events, impact of turbine contamination, and confirmation of plant efficiency [47]. 

The sensor output taken here is the difference in transient response at 2 ms between droplet glucose sample and droplet blank sample. 

The input capacitor (usually on the order of 0.1-/uF disc or a l-/uF solid tantalum) is required if the regulator is more than 4 in. from the power supply filter, and the output capacitor is generally used to improve transient response performance,... 

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