Information about DDMT_170993109001

Published on October 15, 2019

Author: 722446

Source: slideshare.net

2. Window space factor of Transformer :- Window space factor is defined as the ratio of copper area in the window to the area of the window. For a given window area, as the voltage rating of the transformer increases, quantity of insulation in the window increases, area of copper reduces. Thus the window space factor reduces as the voltage increases.

3. It depends upon the relative amounts of insulation and copper provided, which in turn depends upon the voltage rating and output o transformers. The following empirical formulae may be used for estimating the value of window space factor Where kV is the voltage of h.v. winding in kilo-volt. The above formula is for transformers of rating between 50 to 200 kVA.

4. Space factor is larger for large outputs and smaller outputs. For a transformer of about 1000 kVA rating Kw = 12/(30+kV) and for transformers of about 20 kVA rating Kw = 8/(30 + kV). The values of space actor for intermediate rating can be interpolated.

5. For a given window area, as the voltage rating of the transformer increases, quantity of insulation in the window increases, area of copper reduces. Thus the window space factor reduces as the voltage increases. A value for Kw can be calculated by the following emparical formula.

6. where kVhv is the voltage of the high voltage winding expressed in kV. Overall dimensions The main dimensions of the transformer are, (i) Height of window(Hw) (ii) Width of the window(Ww)

7. The other important dimensions of the transformer are, (i) width of largest stamping(a) (ii) diameter of circumscribing circle As the iron area of the leg Ai and the window area Aw = (height of the window Hw x Width of the window Ww) increases the size of the transformer also increases. The size of the transformer increases as the output of the transformer increases.

8. 1. Output-kVA 2. Voltage-V1/V2 with or without tap changers and tapings 3. Frequency-f Hz 4. Number of phases – One or three

9. 5. Rating – Continuous or short time 6. Cooling – Natural or forced 7. Type – Core or shell, power or distribution 8. Type of winding connection in case of 3 phase transformers – star-star, star-delta, delta-delta, delta-star with or without grounded neutral 9. Efficiency, per unit impedance, location (i.e., indoor, pole or platform mounting etc.), temperature rise etc.,

10. Factors Affecting Window Space Factor :- From the definition it can seen that k(w) factor depends upon A(c) and A(w). Now A(c) i.e. area of copper depends upon the rating of transformer. Higher the rating of transformer, higher would be the current hence area of conductor required to carry the current will be larger. A(w) i.e. total window area contains copper area, insulation, air/oil spaces. The insulation used depends upon the voltage.

11. Thus k(w) is affected by voltage rating and KVA rating (output) of transformer k(w) is large large transformer and smaller for small transformer. Window space factor denotes how effectively area of windowis used in the transformer. Higher value of K(w) indicates effective (or efficient) use of window and vice versa.