Reactive loads

After replacing these large induction motors with as many oversized synchronous motors, while the active load at 9325 kW remains the same, the reactive load of induction motors at 785 kVAr will be eliminated and instead a leading reactive load of 5415 kVAr will be added. The net compensation therefore will be... 

Reactive Loads Make demands on electrical system but yield no useful work. 

Z1 internal grid impedance Z2 load impedance RF fault resistance T1, T2 protective devices Q1, Q2 isolating switches K1, K2 short-circuiting devices R1, R2 resistances ofK1, K2 11 fault current generated by the grid I2 fault current generated by a reactive load. 

In case of a fault, the current II - from the power source - feeds RF. It should be emphasized that an additional current 12 flows from the (reactive) load to Rp, due to the stored energy at the load side. This aspect will become important if cable protection is achieved. For other purposes, 12 can be neglected. 

Capacitors and inductors are called reactive loads and their reactance (impedance) is related to the excitation frequency, /, as follows Xi = InfL for inductors and = (2ti/C) for capacitors, where / is the excitation frequency, L is the inductance (in henrys) and C is the capacitance (in farads). The term Inf is sometimes written as co.)... 

In Fig. 9.3 we show a typical general resonance curve as a function of Xa for a structure comprised of two subarrays with reactive loads jXn = —JXli = JXl and with interelement spacing Dj, and. The reference elements of the second array are shifted along the x axis only. 

Switching of harmonic filter banks or capacitor banks on loss of utility power can allow a standby generator to operate at a suitable output power factor when supplying load. Installation of a reactive load bank can provide a further sink for system reactive power if a standby generator is not capable of absorbing the power present in the system. 

To quickly check the junction temperature [Eq. (10.66)] use the 9ja value from the data sheet and the calculated power dissipated for the circuit specihc regulator application. (Note the power calculation may be a simple matter, as in the case of a three-terminal voltage regulator [ ( Vin — Vbur) x /out] J or it maybe more difficult, as in the case of a pulsed input or highly reactive loads. This is considered to be beyond the scope of this work.) If the maximum ambient temperature is not known, it is best to measure it. If that is not possible, an estimate may be made considering the operating environment. In open air, 50°C is not a bad number but in a closed encasement with other electronics, 60°C maybe more reasonable. Automotive and some plant environments are more severe (70-75°C). 

Power factor is an important, but often misunderstood, characteristic of AC power systems. It is defined as the ratio of true power to apparent power, generally expressed as a percentage. (PF also maybe expressed as a decimal value.) Reactive loads (inductive or capacitive) act on power systems to shift the current out of phase with the voltage. The cosine of the resulting angle between the current and voltage is the power factor. 

Phase shifters may also be developed using pin diodes in transmission line networks. One configuration, shown in Fig. 13.69, uses diodes as switches to change the signal path length of the network. A second type uses pin diodes as switches to connect reactive loads across a transmission line. When equal loads are connected with 1/4-wave separation, a pure phase shift results. 

Leading load A reactive load in which the reactance of capacitance is greater than that of indnctance. 

Power amplifiers are generally designed for driving electrically resistive loads. In contrast, unconventional actuators are mainly electrically reactive loads. This section is dedicated to the interaction between the actuator load and the power amplifier, and we will also treat the common amplifier circuit topologies, providing the reader with valuable information that will help him to design his own power amplifier or choose a suitable commercial product. 

This formulation of the principle of virtual work is the principle of virtual displacements, which appears in the hterature sometimes under the name of the preceding. Naturally, the virtual strain energy 6U exists only for mechanical systems with deformable parts. As the contained virtual strain tensor is assembled from derivatives of the virtual displacements, these have to be continuously differentiable. The virtual work of external impressed loads ymd includes the limiting cases of line or point loads. External reactive loads do not contribute when the virtual displacements are required to vanish at the points of action of these loads, and thus the virtual displacements have to comply with the actual geometric or displacement boimdary conditions of Eq. (3.16). With these presumptions, the initial axiom of Remark 3.1 may now be reformulated for the virtual displacements. 

The choice of annual refuelling Implies that the Winfrith SGHWR must operate with a higher mean excess reactivity (and hence fuel Inventory) than the later commercial designs where purely economic considerations are paramount. Moreover the reactor carries a reactivity load in the form of experimental facilities and suffers a higher neutron leakage than commercial reactors due to Its smaller size. All these factors conspire to raise... 

Induction motors give rise to lagging power factor, which can be penalized in the tariffs applied by the utility company. Certain other items of industrial equipment can also contribute to low power factor. This is compensated by coimection of capacitors, either individually for each reactive load, or grouped at a common feed point in the network with banks of capacitors being connected and disconnected automatically in stages as required. Other possibilities for power factor correction include the use of synchronous motors for large drives. 

In DHRUVA, on-line computation of important physics and process parameters has been achieved. The parameters selected are reactor thermal power, reactivity load due to Xenon, core reactivity balance, heavy water system inventory and performance monitoring of shut-off rods control valve and dump valves. Also off-line application for fuel management, failed fuel detection and location, and stores inventory management have been implemented. 

In a reactor like DHRUVA there are primarily two types of reactivity loads which affect the critical height of the moderator in the reactor. 

For ail the operating states of the reactor, a strict vigil has to be maintained on the total inventory of heavy water in the system. Abnormal loss of inventory is indicative of possible degradation of the primary coolant system pressure boundary. Also, the operability of reactor at any power with different operating and experimental reactivity loads is mainly decided by the maximum pumpable moderator height into the reactor vessel which can be computed by knowing the total inventory of heavy water available in the system. 

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