Direct-current generator

This is a very good motor for direct connection to certain loads, particularly where constant speed is required. NEMA defines it as a synchronous machine which transforms electrical power from an alternating-current system into mechanical power. It usually has direct-current field excitation by a separately driven direct-current generator or one directly connected to the motor. This motor remains synchronous with the supply frequency and is not affected by the load. Proper application requires consideration of the following ... 

An industrial direct-current generator is a generator of mechanical construction suitable for industrial use under usual service conditions and has ratings and constructional and performance characteristics applying to direct current generators as given in Parts 11 and 15. 

Metallic copper obtained above is purified by electrolytic refining. The electrolytic cell consists of a cathode made of thin sheets of very pure copper connected to the negative terminal of a direct-current generator, and a lump of extracted impure copper from the ore serving as an anode. A solution of cop-per(II) sulfate in sulfuric acid is used as electrolyte. Electrolysis causes trans-... 

Fig. 25 A macroscopic directional current generated by lines of loop currents [25]. Centers of loop currents are marked by 16 dots in (a) the directional current flows between two lines of loop current centers. In (b) the same directional current given in (a) is depicted with its magnitude indicted by the gray scale...

Regulation 551-04-04 addresses protection against indirect contact for static inverters, typically used for uninterruptable power supplies in installations where continuity of supply is crucial. Where the disconnection times of section 413-02 cannot be achieved, supplementary bonding must be used to minimise the risk of a shock between exposed metalwork. A warning is provided in Regulation 551-04-05 about the possible deleterious effects on the operation of protective devices, such as circuit breakers, of direct current generated by the static inverter or filters. 

In contrast to a direct injection of dc or ac currents in the sample to be tested, the induction of eddy currents by an external excitation coil generates a locally limited current distribution. Since no electrical connection to the sample is required, eddy current NDE is easier to use from a practical point of view, however, the choice of the optimum measurement parameters, like e.g. the excitation frequency, is more critical. Furthermore, the calculation of the current flow in the sample from the measured field distribution tends to be more difficult than in case of a direct current injection. A homogenous field distribution produced by e.g. direct current injection or a sheet inducer [1] allows one to estimate more easily the defect geometry. However, for the detection of technically relevant cracks, these methods do not seem to be easily applicable and sensitive enough, especially in the case of deep lying and small cracks. 

M and A R Leach 1994. Current Methods for Site-Directed Structure Generation. Journal of nputer-Aided Molecular Design 8 467-475. 

Segment plate, used as insulation between copper commutator segments on direct-current universal motors and generators, accounts for the primary use for built-up mica. Phlogopite built-up mica is preferred for these segments because it wears at the same rate as the copper segments. 

Power Take-Off From Engine or Transmission. This type of system is limited to tmcks and there are several take-off means available. Most are some form of electric power generation equipment, belt-driven from the engine crankshaft, which produces either a regulated a-c voltage or rectified direct current for the compressor and fan motors in the body. 

Plasmas can be used in CVD reactors to activate and partially decompose the precursor species and perhaps form new chemical species. This allows deposition at a temperature lower than thermal CVD. The process is called plasma-enhanced CVD (PECVD) (12). The plasmas are generated by direct-current, radio-frequency (r-f), or electron-cyclotron-resonance (ECR) techniques. Eigure 15 shows a parallel-plate CVD reactor that uses r-f power to generate the plasma. This type of PECVD reactor is in common use in the semiconductor industry to deposit siUcon nitride, Si N and glass (PSG) encapsulating layers a few micrometers-thick at deposition rates of 5—100 nm /min. 

Examples of the sacrificial-anode method include the use of zinc, magnesium, or aluminum as anodes in electrical contact with the metal to be protected. These may be anodes buried in the ground for protection of underground pipe lines or attachments to the surfaces of equipment such as condenser water boxes or on ship hulls. The current required is generated in this method by corrosion of the sacrificial-anode material. In the case of the impressed emf, the direct current is provided by external sources and is passed through the system by use of essentially nonsacrificial anodes such as carbon, noncor-rodible alloys, or platinum buried in the ground or suspended in the electrolyte in the case of aqueous systems. 

Bundles of buckytubes were grown, based on an arc method similar to that of Ebbesen and Ajayan[3]. The arc was generated by a direct current (50-300 A, 10-30 V) in a He atmosphere at a pressure of 500 Torr. Two graphite electrode rods with different diameters were employed. The feed rod (anode) was nominally 12.7 mm in diameter and 305 mm long the cathode rod was 25.4 mm in diameter and 100 mm long (it remained largely uneroded as the feed rod was consumed). Typical rod temperature near the arc was in... 

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