A three-winding transformer is connected to an AC source with 50V RMS as shown in the following figure. Voltages induced in the secondary windings are 2V RMS and 8V RMS. The output RMS voltage Vo is
Right Answer is:
The dot marked in the transformer indicates a rise in voltage from the unmarked to the marked terminal on each coil. Under this convention, the current into the dot on the primary side is labeled as having positive polarity, whereas the current out of the dotted terminal on the other side is assigned positive polarity. This means that the power flow must be into the transformer on one side and out of the transformer on the other side.
Applying KVL on the secondary side of the transformer in the given figure.
Vο + 8 − 2 = 0
Vο = −6 V