Discharge devices

Whenever frequent swilehings are likely, high transient voltages may develop and harm the motor windings and the capacitors. Fast discharge facilities must be provided across the capacitor terminals to damp such transients quickly. Sec Section 25.7. for more details on discharge devices. 

In rapidly changing loads it must be ensured that enough discharged capacitors are available in tbe circuit on every close command. To achieve this, sometimes it may be necessary to provide special discharge devices (Section 25.7) across the capacitor terminals or a few extra capacitor units to keep them ready for the next switching. It may require a system study on the pattern of load variations... 

Determine the discharge device for the discharge of a three-phase 6.6 kV, 50 Hz, 1000 kVAr, yconnected capacitor bank, connected in units of 10 x 100 kVAr each, through an automatic p.f. correction relay, having a closing cycle of 10 seconds. Data available from the capacitor manufacturer,... 

This is required to determine the suitability of the resistance of the discharge device to ensure that it discharges a charged capacitor unit or bank at to... 

V or less in 1 minute in LT and in 10 minutes in HT shunt capacitor units or banks and in 5 minutes in series capacitors. The arrangements of discharge devices are illustrated in Figure 25.8. ... 

The use of inadiation or electron bombardment offers an alternative approach to molecular dissociation to the use of elevated temperamres, and offers a number of practical advantages. Intensive sources of radiation in the visible and near-visible are produced by flash photolysis, in which a bank of electrical capacitors is discharged tlrrough an inert gas such as ktypton to produce up to 10 joule for a period of about 10 " s, or by the use of high power laser beams (Eastham, 1986 (loc.cit.)). A more sustainable source of radiation is obtained from electrical discharge devices usually incorporating... 

Fig. 4.36. Diagram of a typical glow discharge device used for GD-OES depth profiling [4.189].

Fig. 4.28. Ionic current / and concentration of nitrogen atoms [N] as functions of the grid potential of the discharge device (the source of nitrogen atoms).

The essential advantage of shock tubes over electric discharge devices is the capability of producing a homogeneous gas sample (HGS) with enthalpy and pressure which can be dependably calculated from the measured shock velocity and the conservation laws. 

There are two more or less exploited types of corona devices—a pin corona discharge device and a wire corona discharge device. These devices are well described by Vaezi-Nejad and Juhasz [3]. 

A pin corona discharge device consists of a stainless steel rod with a sharp conical tip as the corona emitter, a brass hollow cylinder as the corona case, and a perspex cup as the corona holder. Experimental results show that the pin corona current distribution is not uniform, which is one disadvantage of a pin corona device. 

In an attempt to find most efficient corona discharge device for xerographic-spectroscopic purposes, it seems necessary (as the author [4] did) to try various device configurations utilizing sharp pin(s) and wire(s) as the corona emitter. The schematic sketches of three corona devices are shown in Fig. 5.2. 

Figure 15.3 —Ionisation devices, a) Continuous current arc (globular technique). The electrodes are inserted in a series circuit having a variable resistor, a cell and a continuous power source of a few tens of volts b) Glow discharge device using argon (hollow cathode lamp type). Samples can be introduced as powders or non-conductive pellets.

In an electric circuit, pan of which is composed of other than the usual conductor of copper, or other metal, the terminal connecting the conventional conductor and (he conducting substances is an electrode. Examples of electrodes are the electric cell, where they dip in the electrolyte the electric furnace, where the electrodes connect Ihe external circuit with the heating arc the metallic elements in thermionic tubes and gas-discharge devices and in semiconductor devices, where electrodes... 

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