Lab Test Of Single-phase Induction Generator – Lab Report Example
Lab Test of the Single-phase Induction Generator Lab Test Single phase induction generator with load only has one excitation capacitor with auxiliary Winding
The experiment involved carrying out tests on single phase induction generator with load (speed is kept constant) with one excitation capacitor. The induced voltage after starting the induction generator and after increasing the load to the maximum was observed. The differences between the current in the main windings and the current in the auxiliary winding were also observed. The results indicated that induced voltage gradually began to decrease with the increasing load. In this regard, it can be concluded that in a single phase induction motor, any increase in the load causes a reduction in the induced voltage (Bansal 293).
According to many experts, the decreasing induced voltage with the rising load is particularly attributed to the fact that induced voltage is primarily a function of excitation current and speed. For example, the increasing load causes dropping induced voltages as the additional load increases the current. Lastly, with regard to the generator load and output characteristics under different excitation capacitors (constant speed), the tests revealed that the greater the capacitance used, the higher the induced voltage. This is largely based on the fact that single phase induction motors normally depend on the excitation current from the excitation capacitors for the initial voltages. Generally, excitation capacitors are often connected across the auxiliary winding while the external load should be connected to the main winding.
2. Lab Test 2: Single phase Induction Generator with load has two Excitation Capacitor with Auxiliary Winding
In the second experiment, the output characteristics of the induction generator were investigated with load under two different capacitors. For example, the excitation capacitors were connected to the main winding in series and the induced voltage with increasing load as well as the current on the main winding and the auxiliary winding. First and foremost, it was observed that under each excitation capacitor, the induced voltage gradually decreased with the increasing current up to a certain limit (75%) of the speed when the starting winding is finally disconnected thereby leading to a rapid and drastic drop in the induced voltage.
Theoretically, the sudden drop in the induced voltage with further increase in currents is primarily explained by the fact that unlike the case of using one single excitation capacitor with an auxiliary winding, the use of two excitation capacitors involved achieving two phases using a process known as phase splitting. This is particularly achieved by connecting the two non symmetrical phase motors with a main winding as well as with an auxiliary winding. However, the start winding is only used when starting the motor. At the beginning when power is first applied, both windings are usually energized and this results in high induced voltage. However, after when the motor reaches near its operating speed, the start winding is switched off leading to the sudden reduction in induced voltage as observed in the curve of induce voltage versus current for increasing the load.
Comparative Analysis of the Experimental Results
There are a number of similarities as well as differences between the results obtained in Lab test 1 and Lab test 2. For example, with regard to their similarities, both the single phase induction generator with only one excitation capacitor with auxiliary winding as well as the generator with two excitation capacitor with auxiliary winding(split-phase motor) have their induced voltage decreasing with the increasing current. Additionally, both the two motors vibrate mechanically at approximately twice the power line frequency. Lastly, it has also been observed that in both cases, the greater the capacitance used, the higher the induced voltage.
On the other hand, one of the major differences between a single phase induction generator with only one excitation capacitor and the split-phase motor is that the split-phase motor has a significantly high starting current which not only results in excess motor heat during start up but may also cause a serious voltage drop. According to Bansal(296), unlike when only one excitation capacitor, use of two excitation capacitors may require shorter starting periods to help prevent any potential overheating of the windings.
In conclusion, single phase induction motors can effectively work as good generators for a number of household applications some of which include fans, hair dryers and electric kitchen implements among others. This is largely attributed to due to its design simplicity, cost effectiveness and efficiency. However, a major limitation is that their speed is not easy to control and the starting current may sometimes be many times higher than the full load current as is the case with generators with two excitation capacitor auxiliary windings.
Bansal, Ravi. C., “Single-Phase Self-Excited Induction Generators: An Overview,” IEEE Transactions on Energy Conversion, 20.2(2005): 292-299.Print.