Question

1. A 1 ?, 25kVA, 220/440, 60 Hz transformer gave the following test results: Open circuit test (440V side open): 220V, 9.5A, 650W Short circuit test (220 V side shorted): 37.5V, 55A, 950W a) Derive the approximate equivalent circuit (respect to either side) (10) b) Determine the voltage regulation at 90% load, 0.8 PF lagging. (10) c) Draw the phasor diagram for condition (b). (5) d) Efficiency of the transformer for condition (b). (10) e) (Bonus) What is the load KVA for maximum efficiency and the maximum efficiency at 0.9 power factor. (5)

          1. A 1 ?, 25kVA, 220/440, 60 Hz transformer gave the following test results:
Open circuit test (440V side open): 220V, 9.5A, 650W
Short circuit test (220 V side shorted): 37.5V, 55A, 950W
a) Derive the approximate equivalent circuit (respect to either side) (10)
b) Determine the voltage regulation at 90% load, 0.8 PF lagging. (10)
c) Draw the phasor diagram for condition (b). (5)
d) Efficiency of the transformer for condition (b). (10)
e) (Bonus) What is the load KVA for maximum efficiency and the maximum efficiency at
0.9 power factor. (5)

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1. A 1 ?, 25kVA, 220/440, 60 Hz transformer gave the following test results:
Open circuit test (440V side open): 220V, 9.5A, 650W
Short circuit test (220 V side shorted): 37.5V, 55A, 950W
a) Derive the approximate equivalent circuit (respect to either side) (10)
b) Determine the voltage regulation at 90% load, 0.8 PF lagging. (10)
c) Draw the phasor diagram for condition (b). (5)
d) Efficiency of the transformer for condition (b). (10)
e) (Bonus) What is the load KVA for maximum efficiency and the maximum efficiency at
0.9 power factor. (5)

Added by Veronica J.

University Physics with Modern Physics

Hugh D. Young 14th Edition

Instant Answer

Solved by Expert Supreeta N

08/25/2023

Step 1

- Equivalent resistance referred to primary side, R_eq = (V_oc/I_oc) = (220V/9.5A) = 23.16 ohms - Equivalent reactance referred to primary side, X_eq = sqrt((V_oc)^2 - (R_eq*I_oc)^2) = sqrt((220)^2 - (23.16*9.5)^2) = 213.6 ohms - Therefore, the approximate Show more…

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A 1phi ,25kVA,(220)/(440),60Hz transformer gave the following test results: Open circuit test ( 440V side open): 220V,9.5A,650W Short circuit test ( 220V side shorted): 37.5V,55A,950W a) Derive the approximate equivalent circuit (respect to either side) (10) b) Determine the voltage regulation at 90% load, 0.8 PF lagging. (10) c) Draw the phasor diagram for condition (b). (5) d) Efficiency of the transformer for condition (b). (10) e) (Bonus) What is the load KVA for maximum efficiency and the maximum efficiency at 0.9 power factor. (5) b)Determine the voltage regulation at 90% load, 0.8 PF lagging. (10) c)Draw the phasor diagram for condition (b). (5) d)Efficiency of the transformer for condition (b).(10) 0.9 power factor.(5)

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