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A transformer has a primary voltage of 120 V rms and a secondary voltage of 25 V rms. If the secondary current is 1A rms, what is the primary current?
A
7.8 mA
B
208 mA
C
200 mA
D
300 mA
E
None of the above
Correct Answer:
208 mA
A step-down delta-star transformer, with per-phase turns ratio of 5 is fed from a 3-phase 1100 V source. The secondary of this transformer is connected through a 3-pulse type rectifier, which is feeding an R load. The power delivered to the load is 6839.3 Watts. The maximum value of the load current is √2 x 22 A. Fin, the rms value of output voltage Vo (rms)
A
257.3 V
B
220 V
C
261.52 V
D
248.32 V
An AC voltage of 220 V(rms) is applied to the primary of a 10 : 1 step-down transformer. The secondary of the transformer is centre tapped and connected to a full-wave rectifier with a load resistance. The DC voltage appearing the load is
A
$$\frac{{22}}{\pi }$$
B
$$\frac{{31}}{\pi }$$
C
$$\frac{{62}}{\pi }$$
D
$$\frac{{44}}{\pi }$$
A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, the transformer reactance referred to the low voltage side in ohms is __________
A
47.61 Ω
B
15.87 Ω
C
176.33 Ω
D
157.8 Ω
A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, the transformer reactance referred to the low voltage side in ohms is
A
0.1
B
0.2
C
0.198
D
0.4
Suppose a step-down transformer has a turns ration of 5:1. If the secondary current is 1A rms, what is the primary-current?
A
0.3 A
B
0.2 A
C
0.4 A
D
0.6 A
E
None of the above
A step-down transformer has turns ration of 5:1. If the primary voltage is 120 Vrms, what is the secondary voltage?
A
12 V
B
18 V
C
24 V
D
30 V
E
None of the above
The secondary voltage for a certain power transformer is twice the voltage applied to the primary. The current flowing in the secondary winding will be:
A
One-half the primary current
B
Same as the primary current
C
Twice the primary current
D
No more than 10% less than the primary current
E
None of the above
A three phase transformer has a nameplate rating of 30 MVA, 230Y/69Y kV with a leakage -reactance of 10% and the transformer connection is wye-wye. Choosing a base of 30MVA and 230 kV on high voltage side, the transformer reactance referred to the low voltage side will be _______(in ohms).
A
15.87 Ω
B
157.8 Ω
C
176.33 Ω
D
17.67 Ω
A three phase transformer has a nameplate rating of 30 MVA, 230Y/69Y kV with a leakage -reactance of 10% and the transformer connection is wye-wye. Choosing a base of 30MVA and 230 kV on high voltage side, the transformer reactance referred to the high voltage side will be _________(in ohms).
A
176.33 Ω
B
17.67 Ω
C
158.7 Ω
D
15.87 Ω
A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, the transformer reactance on the LV side is ___________
A
176.33 Ω
B
1763.3 Ω
C
47.6 Ω
D
15.87 Ω