EXPERIMENTS ON TRANSFORMER SINGLE PHASE TRANSFORMER (OPEN CIRCUIT AND SHORT CIRCUIT TEST)

Transformer is the very first electrical that is required in making any electrical equipment. This component in turn provides the overall power required, for any system to operate successfully, after necessary isolation, step/up or step/down conditions, as required in the final system. Hence this is the most critical and useful part of any electrical equipment. Therefore it is important to study, understand and experiment, a process, for evaluating its operating characteristics. This knowledge will be utilized, when an engineer is required to design, troubleshot and maintain any electrical system.

Suitable HRC fuses are provided at AC input and DC output stages for protection. The rating of the mains transformer is designed to provide upto 200V DC, while the series transformer provides 40V DC, suitably arranged to provide the correction required. The series transformer is controlled by a three phase motorized dimmerstat. The rectifier circuit is generously rated with suitable heat sink and hole storage suppression.

Objective: Determine the parameters of the equivalent circuit of a single-phase transformer, and to predetermine the performance characteristics and verify the specifications by open circuit and short circuit tests.

1. Study of nameplate ratings of the transformer under test.
2. Determination of Voltage ratio (Turns ratio) test
3. Performing an Open Circuit (OC) Test
4. Performing Short Circuit (SC) Test
5. Determination of Efficiency of the transformer.
6. Draw a graph of performance at UPF and at 0.8p.f.lag.
7. Predetermination of Regulation of Transformer

Scope for inference
As the transformer is inductive load, it takes large in rush current. Select proper fuse rating. Prefer OC test on LV side and SC test on HV side for personnel safety and meter range. On No load, the p.f. of the transformer will be very low. Hence for better results choose LPF wattmeter. During SC test, low voltage is applied, the LV side is shorted by an insulated wire, use proper connection and proper wire. Always switch OFF the supply after taking readings and then start calculations. Do not increase the input voltage beyond the voltage rating of the transformer.