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October 31, 2016

Why is it preferable to generate alternating current rather than direct current?

Alternating current can be changed in voltage by means of transformers. This is necessary because to transmit power over any distance it must be at high voltage. Too much power is lost when transmitting at low voltage. Direct current cannot be changed in voltage without first changing it to alternating current and then raising the voltage; the operation must then be reversed at the receiving end.

On an alternator, does the dc part (the poles) or the ac part (the conductors) rotate?

It is immaterial which part rotates. However, the dc field is usually made the rotating part, and the stator is usually the ac part of the device. This is because the dc field excitation can be of relatively low voltage, and it is easier to insulate a rotating part for low voltage than for high voltage. The ac output is usually a much higher voltage, and it is much more practical to insulate the stator for the high voltage. Also, with this arrangement there are
no brushes required on the output side.

If transformers with different electrical characteristics are connected in parallel, what will happen?

They won’t distribute the load equally; one transformer will tend to assume more of the load than the other. This leads to overheating and, in severe cases, the destruction of the transformer(s).

What is an induction regulator?

This device is similar to a booster transformer. It has a primary and a secondary winding, which are wound on separate cores. The primary can be moved in either direction; this is usually done by an electric motor. In turning, the primary bucks or boosts the line voltage, as required. The amount of bucking or boosting is anticipated by the current being drawn by the line.

What is the relationship between the current and voltage in the high side of a transformer and the current and voltage in the low side of a transformer? Draw a diagram showing this relationship.

With respect to the turns ratio, the current in one side of a transformer is inversely proportional to the current in the other side, whereas the voltage across one side of a transformer is directly proportional to the voltage across the other side. These are illustrated in Figure-1.

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