Autotransformer application pdf

That is why an auto transformer is used for only making small variations in output voltage while using as a step-down transformer. One another major disadvantage of an autotransformer is that the secondary is not isolated electrically from its primary. When we are using it as a step-down transformer , the secondary may cause severe electrical shock, even if it making a very small voltage say 25 V. Because it is electrically not isolated from mains i.

To understand these concepts more clearly, suppose we want to get a 30 AC supply form the V mains. But the latter option is generally avoided because:. Whereas when we use a step-down transformer , we can easily touch the secondary terminal of the operating transformer because its voltage level is very low 30 V and its primary and secondary is completely isolated electrically from each other.

That is, there is no electrical connection between the primary and the secondary. The power is transferred from one circuit to the second circuit only by magnetic flux. Applications of an Auto transformer The auto transformers are used. Your email address will not be published.

Working Principle of Autotransformer The circuit diagram of an auto transformer is shown in Figure. Electrically Transformed Energy in Autotransformer In an autotransformer, energy is transformed into the load by two means, electrically as well as magnetically or inductively. Copper weight of secondary winding;.

The total copper weight of two-winding transformer;. Now, the copper weight ratio of autotransformer to the two-winding transformer;. So the copper saving in autotransformer depends on its turn ratio. As the turn ratio of autotransformer remains less than unity, the copper saving increases when the turn ratio reaches near unity.

The percentage copper saving of an autotransformer can be easily found by taking the ratio of low voltage side to high voltage side. Such as. As the voltage corresponds the turns in the winding, so the percentage copper saving can also be calculated as;. Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. Electrical Technology 0 7 minutes read. Show More.

Related Articles. Leave a Reply Cancel reply Your email address will not be published. Check Also. Close Search for. Further speed increases and the motor achieves its complete rated speed. This motor can be supplied directly from the 3-phase network.

So, to deactivate the motor, switch 3 is released. The auto-transformer starter can be used with any kind of squirrel cage induction motor, which supplies throughout taps of 3-phase autotransformer starter. In this starter, the motor can be connected directly to the secondary winding of the transformer. This transformer is used for starting purpose and the line current is low always as compared to motor nominal current throughout the start, due to the motor connected toward the secondary winding of the transformer starter throughout acceleration.

The variation among motor current and line current will be because of the autotransformer within the circuit. Because of the lower line, the existing autotransformer starter is used to decrease the voltage starter. As the motor starting current is higher as compared to the line current through an autotransformer starter, then the starter will generate more torque for each ampere of line current as compared to any other kind of voltage starter.

Thus, this is all about an overview of autotransformer starter. These transformer ratings are low as compared to the usual motor starter ratings for the higher kW motors.