Autotransformer start

The electric motor is powered at reduced voltage through an autotransformer, which is disconnected from the circuit at the end of the match. The start is made in three times: in the first time, the autotranformador is connected first in star and soon the motor is connected to the network, 1 hp 56c motors through a part of the windings of the autotransformer. The match is made with a decreased tension, which is a function of the transformation ratio. The autotransformer is usually equipped with leads, which allow to choose the ratio of transformation and, therefore, the value of the most appropriate reduced voltage.

Before switching to full voltage, the star connection is opened and the fraction of the winding connected to the network then makes a series-connected inductance such as the motor. This operation is reached when the equilibrium velocity is reached at the end of the first time. The connection to the full voltage is made after the second time, which is morally very short (a fraction of a second). The inductors connected in series with the motor are short circuited and then the autotransformer is disconnected from the circuit.

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