A 100 kVA, 60 Hz, 7200/480 V, single-phase transformer has the following parameters (all expressed in ohms):
RHV = 3.06
RLV = 0.014
XHV = 6.05
XLV = 0.027
Xm,HV = 17,809
Re,HV = 71,400
The transformer supplies a load that draws rated current at 0.75 power factor lagging at 480 V at the load. Sketch the approximate equivalent circuit for this transformer, and determine:
a. the input voltage
b. the efficiency
c. the percent voltage regulation
1. Equivalent circuit for transformer:
Where: R1=RHV =3.06 Ohm, X1 = XHV = 6.05 Ohm
(Voltage Ratio k=E1/E2 = 7200/480= 15)
R2' = (k*k)*RLV = (15*15)* 0.014 = 3.15 Ohm
X2' = (k*k)*XLV = (15*15)* 0.027 = 6.075 Ohm
Re = Re,HV=71400 Ohm, Xm = Xm,HV=17809 Ohm
Since Re and Xm is so large, they can be ignored during the calculation. The equivalent circuit of transformer can be simplified as attached.
2. The input voltage
Since the transformer ...
The solution contains two sketches for part (a) and calculations and explanations. The solution is 325 words.