Feeder power

MSW Feed System, The MSW feed system consisted of a sealed weigh hopper supported by load cells, a 10,2 cm diameter by 102 cm long screw feeder powered by a variable speed DC motor, and a 7.6 cm diameter feed chute fitted with an expansion bellows and a knife gate valve. An air cooler was installed to keep the feed chute near the combustor from overheating. 

Roll and/or force feeder power. To do the required compaction work a certain power input is necessary which must also overcome the losses in the drive system. It was determined that the powder drawn by the roll drive motor(s) is a relatively sensitive indication of the actual work done by the rolls and, therefore, the quality of the product. In machines with fixed rollers the amperage is also a measure of the roll force. 

Account should also be taken of potential changes of duty or use in the lifetime of the equipment. Apart from variations in the product s condition that may arise because of process variations, planned or otherwise, solids commonly vary in condition for a wide variety of reasons. Service conditions also often change in the service lifetime of the equipment. Commonly, feeder duties are up-rated for higher output, formulation changes made, variations of the product s condition, or total product changes made, without any consideration of the effect on feeder power. 

Excitation can also be suppHed by an electromagnetic exciter that uses a rectified, pulsed a-c power supply, or a-c supply to an apposed electromagnet/permanent magnet drive. These units operate at very short strokes and frequencies of 50 to 60 Hz. Although designed primarily as feeders, they are occasionally used as short conveyors. 

Electrical. The plant electrical system is sometimes more important than the steam system. The electrical system consists of the utihty company s entry substation, any ia-plant generating equipment, primary distribution feeders, secondary substations and transformers, final distribution cables, and various items of switch-gear, protective relays, motor starters, motors, lighting control panels, and capacitors to adjust power factor. 

Drying Fhiidized-bed units for drying solids, particularly coal, cement, rock, and limestone, are in general acceptance. Economic-considerations make these units particularly attrac tive when large tonnages of solids are to be handled. Fuel requirements are 3.3 to 4.2 MJ/kg (1500 to 1900 Btu/lb of water removed), and total power for blowers, feeders, etc., is about 0.08 kWh/kg of water removed. The maximum-sized feed is 6 cm (IV2 in) X 0 coal. One of the major advantages of this type of dryer is the close control of conditions so that a predeterminea amount of free moisture may be left with the solids to... 

Vacuum systems (Fig. 21-12h) are characterized by material moving in an air stream of pressure less than ambient. The advantages of this type are that all the pumping energy is used to move the product and that material can be sucked into the conveyor line without the need of a rotaiy feeder or similar seal between the storage vessel and the conveyor. Material remains suspended in the air stream until it reaches a receiver. Here, a cyclone separator or filter (Fig. 21-12c) separates the material from the air, the air passing through the separator and into the suction side of the positive-displacement blower or some other power source. 

Consider the power distribution system of Figure 13.14, having the following feeder details ... 

But they are also rated for the same fault level for which the system is designed as they are connected directly to the system. This is a safety requirement. Similarly, in a draw-out sw itchgear assembly, the 1,/C and O/G power contacts of a module and its mounts (insulators and supports) being already protected may be. suitable only for the thermal rating of their feeders. 

The heat generated by a current-caiTying component or conductor is its watt loss and is expressed by R, where / is the current and R the resistance of the circuit under consideration. The watt loss of each current-carrying component installed in the test assembly is estimated and added to arrive at the approximate watt loss during the actual operation. Based on this loss is calculated of the total heaters required. These heaters are then suitably located in the test assembly to represent all the incoming and outgoing feeders, their power cables and any other current-carrying component. 

Power connections and control wiring The loss within such components is measured by their resistance, which, in the case of cables, is a function of their size and length. The loss in the external power cables is calculated similarly, parts of which run inside the assembly to connect the various feeders, by measuring their average length inside the assembly. 

Each feeder is considered at its optimum rating, based on the current rating of the motor or the rating of the power fuses in a. SFIJ or F.SU feeder while the current may be much less in actual operation. 

Approximate length of wire for each feeder up to the power factor correction relay (PFCR) 35 m. 

These are required to sum the currents in a number of circuits at a time through the measuring CTs provided in each such circuit. The circuits may represent different feeders connected on the same bus of a power system (Figure 15.21(a)), or of two or more different power systems (Figure 15.21 (b)). A preeondition for summation of currents on different power systems is that all circuits must be operating on the same frequency and must relate to the same phase. The p.f. may be different. 

Fach phase of these circuits is provided with an appropriate main CT, the secondary of which is connected to the primary of the summation CT. Summation is possible of many circuits through one summation CT alone per phase. The primary of summation CTs can be designed to accommodate up to ten power circuits easily. If more feeders are likely to be added it is possible to leave space for these on the same summation CT. 

This is the most common scheme in normal use for any power system with more than one feeder, connected to a common bus, such as for distribution and sub-distribution power networks, having a number of load points, controlled through a main incoming feeder. In a switchgear assembly, for instance, common protection may be provided at the incoming for a ground fault or combined 0/C and G/F protections as discussed above. In such cases, a restricted G/F protection may not be appropriate or required, as the protection now needed is sy.stem protection, rather than individual equipment proteelion. The incomer must operate whenever a fault occurs at any point on the system. Moreover, for an LT system, where it may not be desirable or possible to provide individual protection to each feeder, such a scheme is adopted extensively. 

The ground conductor can be of aluminium, GI or copper, as discussed earlier. A humid or a chemically contaminated location is corroding in nature. Aluminium has a rapid reaction and is fast corroding. At such locations, use of GI or copper conductor would be more appropriate. Table 22.4 suggests the ground conductor sizes for aluminium conductor power cable.s for small and medium-ratine feeders when aluminium is used for the ground... 

Consider a power distribution system having the main incoming feeder rated for 400 A and the outgoing feeders rated up to... 

Such protection can be used on a power transformer, a motor or generator, or a single feeder. In addition, other types of relay are used for particular applications (e.g. transformer Buchholz gas, neutral voltage displacement and over-voltage). 

Rotary valves have been specified for the receivers of the vacuum pneumatic conveying systems (RV-601 and RV-602) and for the feeders (RV-40 1) and receivers (RV-501) of the positive-pressure system transferring powder from the dryers to the extruders. Perry72 gives some recommended sizes for rotary valves. The power required by all these valves will probably not exceed 2 kw and will be ignored. 

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