Question

QUESTION 1 125 MARKS] The data in the Table 1 were obtained when open and short circuit test were performed on a single phase 50 kVA, 2400/240 V, 60 Hz transformer. Table 1 Voltage Current Power (V) (A) (Watt) 240 4.85 173 52 20.83 650 Test A Test B (a) Determine tests A, B and the sides the tests were done. Calculate the non-ideal transformer parameters referred to the low voltage side. Draw the equivalent circuit by labeling the parameters and their values. [15 MARKS (b) If the secondary side is connected to a half rated inductive load at 0.8 PF, calculate 15 MARKS (c) A second load is to be connected in parallel to the first load and then connected to the secondary side of the transformer. Determine is it possible to connect the second load if the second load is consuming half of the rated current at 0.85 power factor leading. 15 MARKS]

Answer 1

As short circuit test performed on HV side so refer the parameters of test B on LV side then draw the exact equivalent side

19) Test A – 240V, 4.85A , 173W 1 .' we know No load test is performed at sated low voltage side 80 Test A No load test (Lv side) TestB - 52V, 20.83A , 650W h As Apply voltage is low compare to rated voltage hence Test B Short Ciowit test (Hv side) Short circuit test performed on Hv side by keeping Lu -side short Circuit From test A-240V, 4.85, 173 4085 t 240_o Ro Хм Ic Im 173 240x 4.85 x COSQ = COSD = 1486 4.854 01486 Ic = Io cos Ic 07208A Ima Io sing a 4.7961A 240 240 Rc - Ic *7208 Rc = 332.96352 Lu side Xm 11 240 Im E 240 4.7916 Xm 50.0872 Lv side From test B-528, 20183A, 650W 20.834 Roe jxo 52V 52 12) Rosse + x2 20.83 12 2.496312 II 1² Rse 650 (given) (20183 )* Ree. 650 = 1. 498.9 → Hv side Rse. so X.ge = 2 z? Rose Xee = 1099685 & HV side .. a = 2400 240 so Refer Roel Хge on Lv side (Rselv Ree a2 1.498 014937 100 Xse (Xoelv - 019962 a2 Rse j Xse Ree/2 jkse/2 dia 2 Vo berere Rc og jxm Figure : - Exact Equimalent cirwit refer to Lv [61 Assume HV side is primary Refer to then approx equivalent circuit HV side is II 1.9985. Ip j 1-99621 :1 Is 1 p 14854-81045° NO Rc lalele i Xin 2400V Rc , xm Crefer to Hv side ) Ip = 1485/-31.45€ + 10.416/-36-37° - 3 X 104016 A .. 50Xlo 246 Iga 2 Is = 104.164-36.37 A Is 0.4166-36.370 so I, a A so Ip = 10.766-19.68A V upp Ip ( 1.498+)1,996) + 2400 40° 1) 2 Vp 26. 367/14.431 + 2400_o Vp = 2426.023/615311 80 Up alo ון 10 Vp 242.6023/01581 volt a (0) Is Iz I, = 104.464-36.37 A I,= 4.46/31.78A 80 I, +I2 Is = Is = 172-53-2.5iA ... Rated Is is 50x103 = 208.33 A 240 can yes then it is possible we Connect as overall Is is lower than rated. Scanned with CamScanner