Experiment No. 1

Open-Circuit Saturation Curve of an Alternator

Group No: 7

Leader: Angeles, Vince Aedrian

Group Members: Caliwag, Angela C.

Zaldivar, Nathaniel G.

Grades

Date Submitted: January 20, 2015

Open-Circuit Saturation Curve of an AlternatorAngeles, Vince Aedrian.#1, Caliwag, Angela C.#2,

Zaldivar, Nathaniel G.#3, #Department of Electrical Engineering, Mapua Institute of Technology

Muralla St., Intramuros, Manila, Philippines1vaangeles@mymail.mapua.edu.ph2accaliwag@mymail.mapua.edu.ph3ngzaldivar@mymail.mapua.edu.ph

Abstract—an alternator is an AC generator. In this documentation, the open-circuit curve of an alternator will be shown and observed. The main objective is to observe the relationship between the average voltage and the field current and to record the necessary data for the saturated curve of open-circuit. Still keeping in mind the hysteresis, we expect that the graph shows a curve that has a different increasing and decreasing graph. And as the experiment was done, it was found out that the field current is directly proportional to the average voltage. And that there is a hysteresis in the field.

I. METHODOLOGY

Our first experiment in EE108L aims to obtain the necessary data for the open-circuit saturation curve of an alternator.

We used the following equipment for this experiment:

FH2 MkIV Test Bed FH50 FH100 DMM DC Ammeter R1 V3 Connecting Wires

To be able to perform the experiment we connected the circuit given by our instructor as shown in figures 1 and 2.

Figure 1 Circuit for Stator

Figure 2 Circuit for Rotor

The circuit consists of two parts, one for the stator and the other for the rotor. For the stator, the windings are connected in delta where a voltmeter is connected in each phase. For the rotor, the poles are connected in wye where R and Y are shorter and is connected in series with a DC ammeter. To be able to measure the line voltage, a voltmeter is placed in parallel with line BY The circuit is connected to a 110 V source.

Figure 3 Set up

The additional connection in the circuit is the constant connections for the supply of the prime mover.

After connecting the circuit, we considered the initial setting wherein we must set the speed to 1800 rpm. However, the maximum in speed in our Test Bed is 1500 rpm. The resistance is also initially set to infinity.

To be able to obtain and measure the data required we vary the value of the resistance. As we very the resistance, the values of the field current and line voltages changes. From 0V we slowly increase the resistance up to 20 V. The parameters are measured from 0V then 20V to 100V with an increment of 10V.

After reaching the maximum voltage we reverse the process by measuring from the maximum voltage to 0V.

II. RESULTS AND DATA ANALYSIS

Ef If Vab Vbc Vca Vave

0 0 2.7 2.7 2.7 0

20 80 60 60 60 60

30 140 85 85 85 85

40 180 110 110 110 110

50 230 135 135 135 135

60 270 155 155 155 155

70 310 170 170 170 170

80 360 180 180 180 180

90 400 190 190 190 190

100 430 195 195 195 195

90 380 188 188 188 188

80 340 185 185 185 185

70 300 165 165 165 165

60 260 150 150 150 150

50 220 135 135 135 135

40 160 110 110 110 110

30 130 85 85 85 85

20 80 55 55 55 55

0 0 5 5 5 5

Table 1 Relationship between Parameters

0 50 100 150 200 250 300 350 400 450 5000

50

100

150

200

250

Graph 1 If vs. Vave

From the experiment, as the value of series resistance(R1) was varied, the value of Ef changed from minimum to maximum.

At R1 equal to infinity, Ef was zero(minimum) while at R1 close to 0V, Ef was 100V(maximum). As the values for Ef from 0V to 100V was recorded, it was observed that the value for If was increasing from 0mA to 430mA.

When the Ef was decreased from max to min it was observed that the relationship of it to If is different as to when it was increasing. The trend of the graph when it was increasing is different when it was decreasing.

Regarding the values of Vab, Vbc and Vca, they are all equal in magnitude to each other. Furthermore, it increases/decreases as Ef increases/decreases. For the Vave, it is just the same to the three voltages since those three are simply equal.

III. CONCLUSION

After analyzing the results, it was found out that the average voltage increases as the field current increases. This to say, the average voltage is directly proportional to the field current. Also, when the voltage reached the maximum voltage, another set of trials was done wherein the field current will be decreased, it was found out that the values when the field current is decreasing is different from that when increasing. Thus, it can be therefore concluded that there is hysteresis. It was also found out that the magnitude for the three phases are all equal.

Therefore, in an open-circuit alternator, the curve does not follow back the path.

IV. SCANNED PICTURES OF PDS