Supply systems

Specialty Gases. The specialty gases are generally more reactive than the bulk gases and usually have low volume flow requirements in their appHcations. Historically, these have been deHvered almost exclusively in standard compressed gas cylinders. However, as the need for increased quantities has arisen, bulk specialty gas supply systems utilising larger ton-sized containers and tube trailers are being developed. 

Power Supplies and Controls. Induction heating furnace loads rarely can be connected directiy to the user s electric power distribution system. If the load is to operate at the supply frequency, a transformer is used to provide the proper load voltage as weU as isolation from the supply system. Adjustment of the load voltage can be achieved by means of a tapped transformer or by use of a solid-state switch. The low power factor of an induction load can be corrected by installing a capacitor bank in the primary or secondary circuit. 

The Hanford N Reactor. The Hanford N reactor was built in 1964 for purposes of plutonium production during the Cold War. It used graphite as moderator, pierced by over 1000 Zircaloy 2 tubes. These pressure tubes contained slightly enriched uranium fuel cooled by high temperature light water. The reactor also provided 800 MWe to the Washington PubHc Power Supply System. This reactor was shut down in 1992 because of age and concern for safety. The similarity to the Chemobyl-type reactors played a role in the decision. 

Water-use data and withdrawal rates for public water-supply systems are well documented by municipalities. The U.S. PubHc Health Service (USPHS) (5), American Water Works Association (AWWA) (6—10), and Federal Housing Administration (FHA) (11) have compiled statistics at regular intervals for >23, 000 municipalities in the United States. 

InstaUed cost of a refrigeration system InstaUed cost of a river-water supply system... 

Thrust-Bearing Power Loss The power consumed by various thrust bearing types is an important consideration in any system. Power losses must be accurately predicted so that turbine efficiency can be computed and the oil supply system properly designed. 

High in stalled co.sts. The incremental piping required for the steam supply system and the condensate return system must be installed, insulated, and, in the case of the supply system, additional steam traps are often required. The tracer itself is not expensive, but the labor required for installation is relatively high. Studies have shown that steam tracing svstems typically cost from 50 to 150 percent more than a comparable electric tracing system. 

An interesting feature of these high-temperature-calcination apph-cations is the direct injeciion of either heavy oil, natural gas, or nue coal into the fluidized bed. Combustion takes place at well below flame temperatures without atomization. Considerable care in the design of the fuel- and air-supply system is necessary to take full advantage of the fluidized bed, which sei ves to mix the air and fuel. 

Protection of the electrical supply system in the event of a motor or motor-feeder short circuit. The fault must be cleared from the rest of the system to prevent further trouble,... 

Economics Power-recoveiy units have no operating costs in essence, the energy is available free. Furthermore, there is no incremental capital cost for energy supply. Incremental installed energy-system costs for a steam-turbine driver and supply system amount to about 800 per kilowatt, and the incremental cost of an electric-motor driver plus supply system is about 80 per kilowatt. By contrast, even the highest-inlet-pressure, largest-flow power-recoveiy machines will seldom have an equipment cost of more than 140 per kilowatt, and costs frequently are as low as 64 per kilowatt. However, at bare driver costs (not including power supply) of 64 to 140 per kilowatt for the power-recovery driver versus about 30 to 80 per Idlowatt for... 

After almost 20 years of service, many leaks developed throughout the mill water supply system. Upon inspection, it was found that perforations had occurred beneath large tubercles. Some tubercles were up to 6 in. (15 cm) in diameter. Accessible pipe was water blasted to remove tubercles, and the deepest metal-loss areas (several thousand) were weld repaired. Perforations ceased. 

As standard practice, all motors are designed for a balanced and virtually sinusoidal supply system, but it may not be feasible to obtain the designed supply conditions in practice. Hence, a motor is designed with a certain in-built capacity to sustain small amounts of voltage unbalances and some degree of harmonic quantities, such that the voltage waveform may still be regarded as sinusoidal. 

The performance of a motor is greatly influenced by a voltage unbalance in the supply system. It reduces its output and torque and results in a higher slip and rotor loss. This subject is covered in more detail in Section 12.2(v). For likely deratings, refer to Figure 12.1. Asystem with an unbalance of up to 1 % or so calls for no derating, whereas one having an unbalance of more than 5% is not recommended for an industrial application, because of a... 

A supply system would normally contain certain harmonic quantities, as di.scussed in Section 23.5.2. The influence of such quantities on an induction motor is also discussed in Chapter 23. To maintain a near-sinusoidal voltage waveform, it is essential that the harmonic voltage factor (HVF) of the supply voltage be contained within 0.02 for all 1-0 and 3-0 motors, other than design /V motors and within 0.03 for design N motors, where... 

I hey transform an unbalanced supply system automatically to a balanced supply system through the switching logistics of the IGBTs or the, SCRs. The feature is termed dynamic phase balancing. 

Cuncnt imiisieiits A similar situation will arise wheti a switching ON operation of the rectifier unit occurs hen it is a thyristor rectifier. Under load conditions, the stored magnetic energy in the incoming supply system, which can be the feeding transformer and the line reactances similar to a fault condition discussed earlier, may cause a current transient which can be expressed by... 

The inductor on the input side also suppresses the harmonics in the incoming supply, as high Lj will provide a high impedance path to higher harmonics. For suppression of harmonics, where the supply system is already substtintially distorted, tiddilional L-C... 

Regenerative braking If the motor be run beyond synchronous speed by some external means it will work as a generator and feed back useful energy to the supply system. It will draw only the necessary excitation current, / , for the generator action from the source of supply. In such a condition, the motor... 

Note A supply system having a voltage unbalance of more than 5% is not recommended for an industrial application, which may have a number of electric motors connected on it. Rural distribution, however, is an exception due to excessive LT loads on the same network (Section 7.6), but such loads are mostly individual and not of the industrial type,... 

It measures r.m.s. values to take account of harmonics present in the supply system. 1 1, .. =... 

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