Transformer Efficiency and Regulation - Lab Report Example

LAB EXPERIMENT 2: TRANSFORMER EFFICIENCY AND REGULATTION Name: Course: Instructor: Institution: City: Date: Table of Contents Introduction 3 Apparatus 3 Procedure 4 Results 5 Discussion 6 Conclusion 9 References 9 Introduction A transformer may be defined as an electrical component that employs the principle of electromagnetic induction through mutual induction to “transform” electrical energy from one electrical circuit to another. Usually, the primary winding contains an alternating ac current which produces an equally alternating magnetic flux in the magnetic core of the transformer. Consequently, this alternating magnetic flux generates an alternating voltage in the secondary winding. Essentially, therefore, any load connected to the secondary will receive electrical energy induced to the secondary from the magnetic flux in the primary. This can be illustrated diagrammatically as follows: Figure 1: Illustration of basic transformer operation This experiment, therefore, sought to provide a basic understanding on the operation of a single-phase transformer. This was achieved by validating the interaction between current and voltage in a transformer, and then performing calculations on transformer efficiency and regulation. Apparatus The main distribution board Bench 3-Phase Power Supply (0-240/415V 3-Φ) Connection Leads and Cables Resistive load bank Single-phase transformer AC Bench top Voltmeter 2 × Elcontrol Digital Multimeter One double-pole switch Procedure The experiment circuit was set up as illustrated below: Figure 2: The experimental set up This was achieved by first connecting up the experimental circuit starting with the connections from the load bank to the switch (). The secondary side of the switch was connected to the secondary side of the transformer. This was followed by connecting the primary side of the transformer to the multi-pole switch () available on the bench. The secondary side of the was also connected to terminals 1 and 4 as required. The voltmeter was to be connected in parallel with terminals 1 and 4. Leaving the switch off, the supply voltage was increased to 230 Volts using the raise button on the bench. In order to connect the supply to the primary side of the transformer, the switch was then closed, and the no-load voltages and currents recorded in Table 1. The switch was closed to connect the secondary side of the transformer to the load bank. Slowly, the load was increased until reached its rated current. At each step, the voltage, current, and power measurements were then recorded in Table 2. After all the measurements were taken, the power was procedurally shut down and the circuit disconnected. Results Primary Side Secondary Side 241 134 0 mA 0 mA 0 W 0 W Table 1: The no-load voltages and currents Measurements Quantity Value Load 100 W V1 245 V I1 331 mA P1 56.7 W V2 133 V I2 244 mA P2 27.4 W Load 200 W V1 245 V I1 441 Ma P1 90.7 W V2 133 V I2 495 Ma P2 62 W Load 300 W V1 245 V I1 555 Ma P1 123 W V2 133 V I2 740 Ma P2 94.8 W Load 3000 W V1 245 V I1 3.94 A P1 958 W V2 129 V I2 6.65 A P2 957 W Table 2: Load increase and their corresponding values of voltage, current, and power Discussion In a transformer set up, the parameters in the primary side i.e. current, voltage, and number of coil turns relate to similar parameters in the secondary side. These parameters interact as illustrated by equation 1 below: Equation (i) above is commonly referred to as the transformer’s turns ratio, which essentially is the ratio of the number of turns in the primary winding to the number of turns in the secondary winding. The turns ratio is what determines whether a transformer is either a step-down transformer or a step-up transformer, and to what extent can the transformer can either step down or step up the primary voltage. From this experiment, it was found that the values of P1and P2 were actually different. To be specific, the values of P2 were always smaller than those of P2. Based on the understanding of the operation of step-down and step-up transformers, this difference may be explained by the conclusion that the transformer used in this experiment was a step-down transformer. The full load voltage of the transformer was found to be lower than its rated voltage. This can be attributed to the fact that in a step-down transformer, some voltage is dropped across the resistive and reactive components of the primary side of the transformer courtesy of the primary current. Similarly, there occurs some voltage drop across the resistive and reactive components of the secondary side of the transformer due to the secondary current. It can, therefore, be seen that the full load voltage must just be lower than the rated transformer voltage. From the experiment, and using the formula for the turns ratio shown in Equation (i) above, the following values of the turns ratio can be obtained: Considering the aforementioned values of current/voltage/turns ratio, it can be seen that there were some minor variations with respect to Equation (i). These variations may be due to minor experimental errors, hysteresis losses, and eddy currents losses. It is also notable that the secondary current was higher than the primary current all through for this transformer. Since voltage is inversely proportional to current, a higher voltage implies a lower current and a lower voltage implies a higher current. For a step-down transformer, the primary voltage is higher than the secondary voltage, implying that the primary current is smaller than the secondary current for this transformer. The efficiency of the transformer used in this experiment may be calculated as follows: Similarly, the voltage regulation of the transformer in question may be calculated as follows: Conclusion In conclusion, therefore, it is evident that a transformer is ideally a set of electrical circuits interconnected only through mutual induction. As a result, the primary voltage is transferred to the secondary voltage. It suffices to say, hence, that mutual induction is the foundation of the principle of operation of a transformer. Important to note also is the fact that the transformer efficiency is never 100% due to copper losses and eddy current losses as well. References Bakshi, U. A., & Bakshi, V. U. (2008). Basics for electrical engineering. Pune, India: Technical Publications. Begamudre, R. D. (1998). Electro-mechanical energy conversion with dynamics of machines. New Delhi: New Age International. Blume, S. W. (2007). Electric power system basics: For the nonelectrical professional. Hoboken, N.J: Wiley-Interscience. Dhogal, P. S. (1998). Basic electrical engineering with numerical problems. New Delhi: Tata McGraw-Hill. Herman, S. L. (2011). Electrical transformers and rotating machines. Clifton Park: Delmar Cengage Learning. Read More