Capacitors unit standards

The factors discussed in Section 23.5.2 give rise directly to the current drawn by the capacitor unit and indirectly add to its rating. The relevant Standards on this device recommend a continuous overload capacity of 30% to account for all such factors. A capacitor can have a tolerance of up to -t-15% in its capacitance value (Section 26.3.1(1)). All current-carrying components such as breakers, contactors, switches, fuses, cables and busbar systems associated with a capacitor unit or its banks, must therefore be rated for at least 1.3 x 1.15/,., i.e. 1.54. For circuits where higher amplitudes of harmonics are envisaged, for reasons of frequent load variations or more... 

Below we discuss briefly recommended tests on a finished capacitor unit based on various lEC recommendations. For standards refer to the list provided at the end of the chapter. 

Inductors—be aware that many vendors put cryptic markings such as 102 or 103 on them. For capacitors, there are industry standard markings. For example, 221 is 22 x 1 O pf, 222 is 22 x 102pf, and so on. All are referred to the base unit, pF. But in inductors, 102 may be 10 x 102in nH or pH. In other words they could be a factor of 1000 apart, with the same marking. If necessary, find an LCR meter and double-check. 

The measured insulation resistance is inversely proportional to the capacitance value of the unit being tested. Insulation resistance is a function of capacitance, and hence minimum standards for insulation resistance in the industry have been established as the product of the resistance and the capacitance, RC. For instance, the minimum RC product for ceramic capacitors must be 1 k 2F when measured at 25 C, and it must be 0.1 k 2F at 125 C. 

Farad The standard unit of capacitance equal to the value of a capacitor with a potential of one volt between its plates when the charge on one plate is one coulomb and there is an equal and opposite charge on the other plate. The farad is a large value and is more commonly expressed in microfarads or picofarads. The farad is named for the EngUsh chemist and physicist Michael Faraday (1791-1867). 

Equipment designers have decided that it is sometimes preferable to use components with higher specifications than those strictly necessary for a particular application because they offer better reliability and lower rework costs, a significant factor if their additional cost is far less than reworking. For example, a capacitor rated at 105 C may be a better buy than a standard unit rated at 85 C. 

The VN tube and the main pulse transformer are packaged in a stainless can, 4 in. in diameter and 18 in. high. The can is filled with standard transformer oil so that severe dielectric interfaces between the transformer and tube are avoided. The control unit of the Pulsatron contains the power supplies, energy-storage capacitor, and the thyratron tube... 

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