Step load change

The proportional controller is unable to return the controlled variable to the set point following the step load change, as a deviation is required to sustain its output at a value different from its fixed bias b. The amount of proportional offset produced as a fraction of the uncontrolled offset is 1/(1 + KK ), where K is the steady-state process... 

AIC for a 4 A application, but we would still need to size the core for 5 A We may be able to reduce the copper diameter in going from a 5 A application to a 4 A application, but not the physical size of the inductor, as it must still continue to withstand 5 A, which it would see under sudden step-load changes (or even under normal power-up or power-down). 

Design a minimal prototype algorithm using the following specifications (1) unit step load change and (2) the output should return to zero at the fifth sampling instant and remain at zero for every sampling instant after the fifth. 

N-4b Load fluctuations N-5 Step load changes of+10% of full load N-6 Steady state temperature fluctuations... 

Achenbach (Achenbach, 1995) studied the response of a single cell in a stack to step load change using a 3D transient model. His calculations reveal the relaxation of stack temperature to a steady state on a time scale of the order of 300 s. These calculations were performed imder constant H2 utilization, i.e. the hydrogen flow rate was increased prior to the step change in stack current. It is not clear whether the air flow rate was also increased. If this was the case, increased air flow rate could stabilize the thermal instability induced by the current step. 

The chemical and volume control system provides a means to add and remove mass from the reactor coolant system, as required, to maintain the programmed inventory during normal plant operations. Operations that are accommodated include start-up, shutdown, step load changes, and ramp load changes. 

At prescribed power levels, the dynamic response characteristics of the primary and secondary systems are evaluated. System response characteristics are measured for design step load changes, rapid load reductions and plant trips. 

It is important to see over what range of processes complementary feedback has an advantage over two-mode control. A single-capacity plus dead-time process will respond to a step load change under complementary feedback as shown in Fig. 4.15. Without going into the derivation of the load response curve, it turns out that the integrated area per unit load change is... 

Given a process controlled with a two-mode controller whose proportional band is 200 percent and whose reset time is 10 min, estimate the maximum error developed by a step load change of 5 percent. What would the error be if the same load change were made gradually over an interval of 30 min What would the error be if the load change entered as a sine wave of 5 percent amplitude and 2-hr period ... 

The peak will occur about 2 min following a step-load change because this is the point of greatest departure between the curves. Lead time should be about 1.6 min, and lag time about 3 min. 

Df(z) can be determined from equation (21.13) once the nature of the load and the process model are known. Let us calculate the feedforward algorithm for a feed-composition disturbance from the infexmation in Table 21.1 for a step-load change. 

---