Question

EE 488 HW 15 For the three-phase transformers shown, the individual windings are rated: primary "H" winding 7200v secondary "X" winding 480 V tertiary "M" winding 1.4 kv The primary winding is connected to a balanced 13.2 kV (ine-line) positive sequence three-phase source. a. Calculate the 3-phase turns ratio and phase shift from the primary to the secondary windings. b. Calculate the 3-phase turns ratio and phase shift from the primary to the tertiary windings HC ХВ nA XA HA

Answer 1

Given:

V_P-L-L=V_P-L-N =13.2KV

Rated Individual Windings Voltage

H = 7.2KV

X = 0.48KV

M = 1.4KV

Assumption:

Let us assume that the Voltage rating of the H windings are given as V _L-N

Proof:

a.

The turn ratio for Primary and H winding is V_P-L-N  / V _{S- L-N} = 13.2/7.2 = 1.833, Here the phase difference is 30^o because of different windings

Now for the Primary and X windings, the turns ration is V_P-L-N  / V _{S- L-N} = 13.2 / 0.48 = 27.5, Here the Phase shift is 0^o between primary and secondary because of similar windings.