Indepth Electrical engineering

Short-Circuit Test on Transformer 1. Purpose of Short-Circuit Test To determine copper (I²R) losses of the transformer at full load. To calculate the equivalent resistance and impedance of the transformer. Performed on High-Voltage (HT) side (not LT) since rated current is much lower and easy to achieve. 2. Why Conduct Test on HT Side? Rated current on HT side is lower than LT side. Applying small test voltage (~5–6% of rated voltage) on HT winding produces rated current. If performed on LT side, the HT winding would short to zero volts, causing dangerous high current and risk of winding damage. 3. Principle of the Test Core losses are negligible (since applied test voltage is very small). Wattmeter reading = copper losses at rated current. 4. Connection Diagram Ammeter, Voltmeter, and Wattmeter connected on HT winding . LT side short-circuited . Variac (auto-transformer) used to gradually increase applied voltage until rated current ...

Open Circuit (No Load) Test on Transformer The Open Circuit Test , also known as the No Load Test , is performed on a transformer to determine its core losses (iron losses) under no load conditions. Purpose of the Test To measure core losses (hysteresis and eddy current losses) in the transformer. To calculate parameters of the equivalent circuit (shunt branch) . To determine the magnetizing current . Why High Voltage Side is Kept Open? In the open-circuit test, one winding of the transformer is left open . The high-voltage (HV) winding is kept open , and the test is performed from the low-voltage (LV) side . This is because: At rated HV, the current is very small (hard to measure accurately). Instruments required for HV would need higher insulation and safety. So, LV side is used for practical measurement. Test Connections A Voltmeter , Ammeter , and Wattmeter are connected on the LV side . The HV side is left open . Supply is app...