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Data and Results :

Table 5-1

Step Up TransformerEp Es Ip Is EpIp EsIs

109 V 214 V 1.1 A 0.5 A 117.7 VA 107 VA*Using 25 Watt-Bulb

Table 5-2

Step Down TransformerEp Es Ip Is EpIp EsIs

108 V 109 V 0.39 A 0.31 A 42.12 VA 33.39 VA*Using 25 Watt-Bulb

Reactions :

At the end of the experiment, we observed that using VARIAC Transformer is analternative equipment for an autotransformer and we may create Ste Up and Step DownTransformer by following the circuit diagrams illustrated in the laboratory manual. It was

quite delicate for the connections and so extra care is strictly observed. For the set of equipment we have used, we noticed that some has an inaccurate reading, for example, theVARIACs turned in 220 volts, when measured in multimeter measures 224 volts. As asolution, we set correctly the VARIACS according to the multimeter. The members learnedthe relationship between the voltage and the current, especially in getting their values. For the Step Up Transformer with a final voltage of 220 volts, the lamps connected in parallel are

brighter compare to a dimmer light in Step Up Transformer because it has stepped voltage of 110 volts (having small currents, not enough brighten the lamps). It clearly shows how tocreate an improvised Step -up Transformer and Step-down Transformer through theapplication of the VARIAC

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Conclusion :

Autotransformer is a special type of transformer which typically has only onewinding. It is often used to step up or step down voltages in the 110-115-120 volt range andvoltages in the 220-230-240 volt range. The autotransformer can slightly increase the voltage,moreover, it can also slightly decrease the voltage based on the required output voltage. Thereis a single winding that is common to both secondary and primary windings. In an autotransformer, the primary and secondary windings are both electromagnetically and electricallycoupled.

The experiment composes of two parts: the Step Up transformer and the StepDown Transformer. We used two VARIAC Transformer (Variable AC Transformer) as anautotransformer for the Step Up and Step Down Transformer, with a both source of 220 volts.

For the Step Up Transformer (110 to 220 volts), with 110 volts reading both for the first andsecond VARIAC. Meanwhile for the Step Down transformer (220 to 110 volts), the first andsecond VARIACS, read 110 and 220 volts, respectively. The VARIACS for the twotransformers are connected the same, the output of the first is connected to the output of thesecond VARIAC to deliver 220 volts for the Step Up, and 110 volts for the Step Downtransformer. Each transformer is connected in one of the lamps which are connected in

parallel.

On the other hand, the voltage and current relationship for this experiment iscommon for a usual experiment. The voltmeter is parallel-connected in the output of thesecond VARIAC to get the Primary voltage (E p), and for the Secondary Voltage (E s) in one of the lamps, separately measured. For the current, the ammeter is series-connected between thefirst and second VARIAC to measure the Primary Current (I p), and between the secondVARIAC and one of the lamps to measure the Secondary Current (I s).

Therefore, an autotransformer may achieve through the presence of the VARIACTransformer. This experiment needs extra care because of the AC source. The connectionsmust be strictly observed, especially in measuring the voltages and currents.