Autotransformer An autotransformer is a special type of transformer used in control systems where the input and output are alternating current (AC) volta...
An autotransformer is a special type of transformer used in control systems where the input and output are alternating current (AC) voltages with the same frequency. It serves as a current-balance device for the closed-loop control system and helps to achieve precise control of the output voltage regardless of changes in the input voltage.
Key features:
The autotransformer has two windings connected in series, each with its own separate DC current.
The two windings are connected at their star points and share a common ground connection.
Both windings are fed by the same alternating current source, and the turns ratio determines the ratio of the output voltage to the input voltage.
The autotransformer acts as a voltage divider and a current transformer, simultaneously.
Operation:
When the input voltage is applied, it is divided equally between the two windings through the turns ratio.
This means that the output voltage is also divided by the turns ratio.
If the input voltage is higher than the output voltage, the autotransformer acts as a voltage divider, reducing the output voltage to match the input voltage.
If the input voltage is lower than the output voltage, the autotransformer acts as a current transformer, increasing the output voltage to match the input voltage.
Benefits:
The autotransformer simplifies the control system by eliminating the need for a separate voltage source and transformer.
It ensures constant output voltage regardless of changes in the input voltage, maintaining system stability.
This makes it particularly useful in applications where precise voltage control is crucial, such as in power supplies, medical equipment, and industrial control systems.
Additional points:
The autotransformer is a highly efficient device, with high efficiency usually exceeding 99%.
It is typically used in conjunction with control loops to achieve precise and robust control of the output voltage.
The turns ratio of the autotransformer is typically set using a variable transformer or a potentiometer