Dry Type Transformer
Types of Dry Type Transformers
Cast Resin Dry Type Transformer (CRT)
This type of transformer has following advantages. They are-
Disadvantages of Dry Type Transformer
Application of Dry Type Transformer
Important Factors to Design a Dry Type Transformers
3. Selection of Core Material with Low Hysteresis Loss
The core of the transformer must have high permeability and less hysteresis loss in order to have better efficiency. The CRGO stell is used for the core material . The CRGO steel offers higher permeability and the minimum hysteresis loss.
The leakage reactance of the transformer must be as minimum as possible to get better voltage regulation of the transformer.The regulation of the transformer shows drop in the secondary voltage with increase of loading on transformer. The leakage reactance is generally kept within 2 % during transformer design.
The life of the transformer depends upon the useful life of the insulation. The life of the insulation is dependent on the temperature. The rise in temperature cause deterioration in the insulation value which may further cause breakdown of the insulation. Insulation class B, F and H is preferred for dry type transformer to withstand higher temperature. The temperature rise must be calculated during desin stage of the transformer to get higher life expectancy of the transformer.
The no load losses of the transformer depends on the eddy current and hysteresis loss. The no load losses can be minimized by use of the CRGO core and by keeping the leakage reactance as minimum as possible. The load losses depends on the resitance of the conductor. Thus, by keeping the winding resistance within moderate value losses, voltage regulation and the efficiency of the transformer can be improved.
If the load on the transformer increases above its rated kVA, the transformer is said to be overloaded. The overloading cause rise in temperature of the transformer which reduce the useful life of the transformer. The cooling system should be designed to cater the temporary overloading of transformer.
If the dry type transformer is to be used for supplying the current to non-linear loads the temperature rise takes place due to harmonics in the current waveform. The transformer for such application must be assigned K-factor.
9. Insulation Level
In transformer design, insulation level adjustment is an important factor. Generally insulation level is chosen as per basic impulse level and system over voltage. Strong insulation level increases the life of a transformer.