Statement-wise Verification

• Statement 1 - Correct.
  The open-circuit test is conducted to determine core losses and magnetizing current at rated voltage conditions.
  In the OC test the secondary is open and rated voltage is applied to the energized side; input power is approximately core loss because current is small.
• Statement 2 - Correct.
  The short-circuit test is used to determine copper losses and equivalent impedance of the transformer.
  In the SC test a small applied voltage produces rated current; input power at rated current is approximately full-load copper loss and measured V/I gives equivalent impedance.
• Statement 3 - Incorrect.
  In the open-circuit test, rated current flows in the primary winding during the test.
  Open-circuit current is only a small percentage of rated current, not rated current.
• Statement 4 - Correct.
  In the short-circuit test, a reduced voltage is applied to circulate rated current in the windings.
  Only a reduced fraction of rated voltage is needed during the SC test to circulate rated current because transformer leakage impedance is small.

Core Concept

OC and SC tests separate transformer loss components without loading the transformer fully. OC emphasizes shunt/core behavior; SC emphasizes series/leakage behavior. This is why they can be used to predict regulation and efficiency economically.

Formula / Key Relationship

OC: P0 ≈ Pi(core). SC at rated current: Psc ≈ Pcu,FL; Zeq = Vsc/Isc; Req=Psc/Isc².

Step-by-Step Check

Test conditions, current magnitudes and power readings independently agree with statements 1, 2 and 4 and reject 3. Option A exactly matches.

Why the Other Options Are Wrong

Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.

Answer-Key Verification Note

The uploaded provisional key marks C . After independent technical verification, the defensible answer is A . This discrepancy is stated explicitly rather than silently copying the provisional key.

Exam Shortcut / Approach

OC → rated voltage, small current, core loss. SC → rated current, small voltage, copper loss.

Common Mistake

Confusing “rated voltage” in OC with “rated current”; the OC current is deliberately small.

Quick Revision

Open-Circuit and Short-Circuit Tests is linked with Transformer Tests, Transformers and Electrical Machines. OC → rated voltage, small current, core loss. SC → rated current, small voltage, copper loss.

Statement-wise Verification

• Statement 1 - Correct.
  The open-circuit test is conducted to determine core losses and magnetizing current at rated voltage conditions.
  In the OC test the secondary is open and rated voltage is applied to the energized side; input power is approximately core loss because current is small.
• Statement 2 - Correct.
  The short-circuit test is used to determine copper losses and equivalent impedance of the transformer.
  In the SC test a small applied voltage produces rated current; input power at rated current is approximately full-load copper loss and measured V/I gives equivalent impedance.
• Statement 3 - Incorrect.
  In the open-circuit test, rated current flows in the primary winding during the test.
  Open-circuit current is only a small percentage of rated current, not rated current.
• Statement 4 - Correct.
  In the short-circuit test, a reduced voltage is applied to circulate rated current in the windings.
  Only a reduced fraction of rated voltage is needed during the SC test to circulate rated current because transformer leakage impedance is small.

Core Concept

OC and SC tests separate transformer loss components without loading the transformer fully. OC emphasizes shunt/core behavior; SC emphasizes series/leakage behavior. This is why they can be used to predict regulation and efficiency economically.

Formula / Key Relationship

OC: P0 ≈ Pi(core). SC at rated current: Psc ≈ Pcu,FL; Zeq = Vsc/Isc; Req=Psc/Isc².

Step-by-Step Check

Test conditions, current magnitudes and power readings independently agree with statements 1, 2 and 4 and reject 3. Option A exactly matches.

Why the Other Options Are Wrong

Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.

Answer-Key Verification Note

The uploaded provisional key marks C . After independent technical verification, the defensible answer is A . This discrepancy is stated explicitly rather than silently copying the provisional key.

Exam Shortcut / Approach

OC → rated voltage, small current, core loss. SC → rated current, small voltage, copper loss.

Common Mistake

Confusing “rated voltage” in OC with “rated current”; the OC current is deliberately small.

Quick Revision

Open-Circuit and Short-Circuit Tests is linked with Transformer Tests, Transformers and Electrical Machines. OC → rated voltage, small current, core loss. SC → rated current, small voltage, copper loss.

Statement-wise Verification

• Statement 1 - Correct.
  The open-circuit test is conducted to determine core losses and magnetizing current at rated voltage conditions.
  In the OC test the secondary is open and rated voltage is applied to the energized side; input power is approximately core loss because current is small.
• Statement 2 - Correct.
  The short-circuit test is used to determine copper losses and equivalent impedance of the transformer.
  In the SC test a small applied voltage produces rated current; input power at rated current is approximately full-load copper loss and measured V/I gives equivalent impedance.
• Statement 3 - Incorrect.
  In the open-circuit test, rated current flows in the primary winding during the test.
  Open-circuit current is only a small percentage of rated current, not rated current.
• Statement 4 - Correct.
  In the short-circuit test, a reduced voltage is applied to circulate rated current in the windings.
  Only a reduced fraction of rated voltage is needed during the SC test to circulate rated current because transformer leakage impedance is small.

Core Concept

OC and SC tests separate transformer loss components without loading the transformer fully. OC emphasizes shunt/core behavior; SC emphasizes series/leakage behavior. This is why they can be used to predict regulation and efficiency economically.

Formula / Key Relationship

OC: P0 ≈ Pi(core). SC at rated current: Psc ≈ Pcu,FL; Zeq = Vsc/Isc; Req=Psc/Isc².

Step-by-Step Check

Test conditions, current magnitudes and power readings independently agree with statements 1, 2 and 4 and reject 3. Option A exactly matches.

Why the Other Options Are Wrong

Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.

Answer-Key Verification Note

The uploaded provisional key marks C . After independent technical verification, the defensible answer is A . This discrepancy is stated explicitly rather than silently copying the provisional key.

Exam Shortcut / Approach

OC → rated voltage, small current, core loss. SC → rated current, small voltage, copper loss.

Common Mistake

Confusing “rated voltage” in OC with “rated current”; the OC current is deliberately small.

Quick Revision

Open-Circuit and Short-Circuit Tests is linked with Transformer Tests, Transformers and Electrical Machines. OC → rated voltage, small current, core loss. SC → rated current, small voltage, copper loss.