BADRY TRANSFORMERS
DRY-TYPE TRANSFORMERS MANUFACTURE
DRY-TYPE TRANSFORMERS:
INTRODUCTION
Transformer is a static electromagnet device having two or more inductively coupled windings which are located on a magnet core and designed for conversion by electromagnetic induction of one or multiple AC systems (voltages) into one or multiple other systems (voltages), without frequency change.
Since the time of the discovery of electromagnetic induction, a plenty of researches and experiments were conducted, before transformers had become such as we are accustomed to, in terms of their design performance. The design of transformers was constantly becoming more and more perfect, including due to development of new insulation materials.
At present, the following standard designs of transformers are offered:
- cast coil dry-type transformers;
- air-barrier insulation dry-type transformers;
- oil-immersed transformers.
CAST COIL DRY-TYPE TRANSFORMERS
Dry-type transformers HV windings whereof are cast with a special compound are referred to as cast coil drytype transformers. Demonstrating good performance, this type of transformers is applied all over the world, and the specific number of cast coil transformers is constantly growing. Due to a large experience of practical application, this design is being constantly perfected.
A range of applied voltage and power values is being expanded as well.
AIR-BARRIER INSULATION
DRY-TYPE TRANSFORMERS
Air-barrier insulation was used in the first models of transformers, even before application of oil dielectric material. A typical design of windings of such transformer is conductors with an insulation of distance (in form of air barriers) left between them. The conductors are coated with film or paper insulation. Transformers of such type are used but to a limited extent, not over 10% of the total
number of dry-type power transformers.
To provide protection of conductors insulation, windings of such transformers should be impregnated in deep vacuum. As time passes, air gaps can be contaminated with dust which leads to deterioration of dielectric properties of insulation.
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Contrary to general ideas, windings with air barrier insulation made in industrial environment cannot receive high-quality repair on site.
OIL-IMMERSED TRANSFORMERS
Oil-immersed transformers are featured with use of transformer mineral oil as the main dielectric. In other aspects, the design of oil-immersed transformers is similar to that of air-barrier insulation transformers.
Oil acts as an electric insulation and cooling medium.
Due to temperature affect, oil can become contracted or expanded in its volume. To compensate this effect, corrugated-wall tanks are used, or the design can provide availability of an expansion tank which is installed over the general oil level.
Mineral oil under effect of internal and external factors can partially lose its dielectric properties, as time passes.
To maintain the standardized characteristics, one have to monitor the oil level, quality and hermeticity of tanks.
Inflammability of transformer oil can be regarded as its large disadvantage. Under a certain temperature or a flash, oil can be inflamed and burn by itself, regardless of the rate of elimination of factors of inflammation.
Rapid expansion of gases emitted with burning can lead to an explosion. In high-capacity power transformers these risk factors are struggled against on all levels:
from integration of extra monitoring systems in the design to regular inspections and evaluation of the
equipment condition.
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