Transformer assembly

Greenland S, Salvan A, Wegman DH, et al. 1994. A case-control study of cancer mortality at a transformer-assembly facility. Int Arch Occup Environ Health 66 49-54. 

Analysis was for all workers in the transformer plant, with definite , probable , or possible link between death and pancreatic cancer. The definite pancreatic cancer mortality cases yielded an SMR of 2.92 (95% Cl=1.17-6.01). Among all workers employed for 6 months (n=812) an SMR of 7.64 (3.29-15.06) was obtained, and among workers employed for 6 months in the transformer assembly department (n=308), an SMR of 12.9 (2.59-37.7) was calculated. The authors noted that considerably more exposure to mineral oils occurred than exposure to PCB-containing askarol transformer fluids. Wong (1995) identified other concerns about the positive pancreatic findings, including inclusion of cases that had neither sufficient duration of exposure nor sufficient latency to be related to PCB exposure at the plant. 

Statistically non-significant SMRs were obtained in separate analyses for non-Hodgkins lymphomas and leukemias in all workers employed for 6 months (n=812) and in transformer assembly workers employed for 6 months (n=308). The authors noted that considerably more exposure to mineral oils occurred than exposure to PCB-containing askarol transformer fluids. 

A molten metal alloy would normally be expected to crystallize into one or several phases. To form an amorphous, ie, glassy metal alloy from the Hquid state means that the crystallization step must be avoided during solidification. This can be understood by considering a time—temperature—transformation (TTT) diagram (Eig. 2). Nucleating phases require an iacubation time to assemble atoms through a statistical process iato the correct crystal stmcture... 

These assemblies are fitted with switching devices (breakers, switches, fuse switches and contactors etc.) and control and measuring instruments, indicating, regtilating and protective devices etc. to transform the assemblies into composite units, called control centres to perform a number of functions in the field of distribution and control of electrical power. Some of these functions may be one or more of the following ... 

During the test, one pole of the testing transformer should be connected to ground and the frame of the assembly. 

The same conditions would apply as for a switchgear assembly (Section 13.4.2). Unlike a controlgear or a switchgear assembly, a bus system may be required to be partly located outdoors. This is true for most installations, as the switchyard is normally located outdoors as is the feeding transformer, while, the switchgears are located indoors, to which the bus system is connected. 

Instrument transformers (CTs, class PS, CT, VTs and CVTs etc.) form important components of a switchgear assembly for measurement and protection. They are covered for their specifications, selection and application. 

Although development work on shellac in blends with other synthetic resins has been carried out over a period of time, the only current use in the plastics industry is in the manufacture of electrical insulators. At one time electrical insulators and like equipment were fabricated from mica but with increase in both the size and quantity of such equipment shellac was introduced as a binder for mica flake. For commutator work the amount of shellac used is only 3-5% of the mica but in hot moulding Micanite for V-rings, transformer rings etc., more than 10% may be used. The structures after assembly are pressed and cured, typically for two hours at 150-160°C under pressure. 

Metallurgists originally, and now materials scientists (as well as solid-state chemists) have used erystallographic methods, certainly, for the determination of the structures of intermetallic compounds, but also for such subsidiary parepistemes as the study of the orientation relationships involved in phase transformations, and the study of preferred orientations, alias texture (statistically preferential alignment of the crystal axes of the individual grains in a polycrystalline assembly) however, those who pursue such concerns are not members of the aristocracy The study of texture both by X-ray diffraction and by computer simulation has become a huge sub-subsidiary field, very recently marked by the publication of a major book (Kocks el al. 1998). 

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