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Examoogle • User • info@examoogle.com • EE-2024-8821
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Which special tests performed on transform?
Voltage ratio
Slip
Voltage vector
A and C
A and C
Quick Summary: Special tests for transformers are conducted to verify design parameters and ensure compliance with site standards during installation and commissioning. Both Voltage Ratio and Voltage Vector Group tests are mandatory routine and special tests to ensure the transformer operates correctly within the power system network.
Special tests for transformers are conducted to verify design parameters and ensure compliance with site standards during installation and commissioning. Both Voltage Ratio and Voltage Vector Group tests are mandatory routine and special tests to ensure the transformer operates correctly within the power system network.
K=VsecondaryVprimary=NsecondaryNprimary — Voltage Ratio formula
Δϕ=∠VH−∠VL — Vector Group displacement formula
The Voltage Ratio test confirms the turn ratio K=N2N1=E2E1 to ensure the secondary output aligns with specifications. The Vector Group test uses phase-angle measurement to verify the relative phase displacement between high-voltage and low-voltage windings, which is critical for successful parallel operation of transformers.
Voltage ratio test ensures no internal short-circuited turns exist in the windings.
Vector group test is vital when transformers need to be connected in parallel.
These tests are performed during pre-commissioning to ensure the health of the insulation and winding structure.
Slip is a parameter associated with induction motors, not transformers, making it a distractor.
Prevents phase mismatches during grid synchronization
Ensures accurate secondary voltage output for sensitive loads
Requires high-precision bridge instruments
Time-consuming during field site installation
Power transformer factory acceptance testing
Post-repair maintenance verification
The Slip parameter is calculated as s=NsNs−Nr, which is specific to rotating induction machinery and irrelevant to static transformer devices.
Vector group nomenclature (e.g., Dyn11) describes the phase shift; testing confirms the winding arrangement matches the nameplate.
D is correct — Both the voltage ratio and the voltage vector group are critical verification tests for transformer commissioning.
Always remember that transformer tests are static (DC resistance, ratio, ratio, vector), while motor tests involve dynamic parameters like slip and torque.