Question

generator with a rated field current of 5 A was tested, and the following data were taken: a. VT,oc at rated Is was measured to be 500 V b. IL,sc at the rated It was found to be 250 A. When a dc voltage of 20 V was applied to two of the terminals, a current of 45 A was measured. c. Draw per phase equivalent circuit of the generator at rated condition.

A 200 - kVA, 480 V, 50 Hz, Y connected synchronous generator with a rated field current of 5 A was tested. The following data were taken

VT,oc at rated IF was measured to be 500 V

IL,sc at the rated IF was found to be 250 A

When a rated DC voltage of 20 V was applied to 2 of the terminals, a current of 45 A was measured.

Draw the per phase equivalent circuit of the generator at rated condition

Answer 1

For the given values of test results, the required equivalent circuit is drawn using the calculations as shown below :

200 KVA 480 V, 50 HZ, Y connection of synchoonous generator Rated field current 5A Data taken is : (Yos 500 V at rated IF = 5 A 6 Ilse = 250 A at rated IF © when De voltage of 200 is applied, I = 454 a De-voltage is applied As generator between its two phases generator is Y-connected SO Voc (RA+RA) - IDC Voc = 2ov w ARA Voc Ipc w 20 RA = 0.22 m 2 (45) R = 0.22 n no roltage Internal generated EA = (Voc at rated I (field current) is V V3 V3 500 - 288.675 Volts

Synchronous reactance at rated field current is Xo Ve BR - RA Asc (288.675) (250) - (0.222) - - 2 So, Хs = 1.133 n EA 288.675 ²1.15 h 250 If Xs (approximate method) - (I also Error ignoring RA is much smaller than error to core saturation. RA А IF = 5A w 0.222 1 jl. 1.334 EA = 288.675 V + VE LE Equivalent Circuit

So the equivalent circuit is as above for the given testing conditions.