Generally transformer can be classified as;
- Based on the number of phases: single or 3 phase
- Based on the nature of the magnetic media: core or shell type construction
- Based on the loading condition: power or distribution types
Designing features of power Transformers and Distribution transformers
Loading on the transformer are going to be at or close to the full load throughout the retro of operation. Once the load is a smaller amount, the transformer which is in parallel with other transformers, is also place out of service.
Generally designed to realize maximum efficiency at or close to the full load. Thus iron loss is formed adequate to full load copper loss by employing a higher value of flux density. In alternative words, power transformers are usually designed for the higher value of flux density.
Requirement of voltage regulation doesn't arise .The voltage variation is obtained by the assistance of tap changers provided usually on the high voltage tap. Commonly Power transformers are deliberately designed for the higher value of discharge transformer, so the short-circuit current, impact of mechanical force and hence the damage is a smaller amount.
In distribution transformer load on the transformer doesn't stay constant however vary instant to instant throughout the entire day.
Generally designed for max efficiency at regarding 0.5 full load. So as that the all-day potency is high, iron loss is formed less by choosing a lesser value of flux density. In an alternative words distribution transformers are usually designed for a lesser value of concentration.
Since the distributed transformers are situated within the section of the load, voltage regulation is a crucial issue. Generally the distribution transformers aren't equipped with tap changers to keep up a continuous voltage because it will increase the value, maintenance charges etc., so the distribution transformers are designed to have low value of inherent regulation by keeping down the value of leakage reactance.
Note: % of regulation = [(I1Rp Cosø ± I1Xp Sinø)/V1)] x 100 value of leakage reactance is less when the value of leakage reactance Xp is less, as the primary current I1 is fixed & resistance of the transformer Rp is nearly tiny. Ideal value of regulation is zero.