We know that in ordinary transformers primary and secondary windings are magnetically connected while in autotransformers a winding is used which is tapped from the centre and electrically connected. An ordinary transformer has no magnetic coupling and mutually induced current and the autotransformer has a self. Inspired EMF. We can use this transformer step as well as captain, but generally, we use this transformer below.
V1 = primary applied voltage
V2 = secondary voltage across the load
i1 = primary current
i2 = nordcurrent
N1 = number pattern between a and b
N2 = the number of trains between C and B.
Image Source- Google
In the diagram terminal, a and b are called primary windings and terminals c and b are called secondary windings. The secondary winding has less number of tan as compared to primary winding as we are using this transformer as a step-down transformer. Current flow in the primary winding is I1 and current flow in the secondary winding is I2
The number between A and c is N1 – N2. And the secondary winding has the number of turns and N2-N1. And the law is connected between C and B which is the secondary winding. And terminal c can be called a rotary switch. With the rotary switch, we can adjust the voltage. Here is the picture of the rotary switch.
It is a 1 kVA autotransformer that supplies single phase 50 Hz. And there is the rotary switch which you can see in the picture black knob associated with terminal C in the internal circuit.
Always remember -
• If the number of turns in the primary is more than the secondary, it is called step down transformer.
• And if the number of windings in the secondary winding exceeds the primary winding, it is called a step-up transformer.
Change ratio
K = V2 / V1 = E2 / E1 = i1 / i2
K <1 always
Benefit
The autotransformer has only one winding so the copper consumption is less.
Less expensive.
Less loss than two winding transformers.
Low leakage flow.
loss
The main disadvantage of autotransformer by secondary winding is not insulated from primary winding if we use the transformer as a step-down transformer and if the secondary winding is broken then all the full load primary voltages fall into the secondary winding which is hazardous to the operator. As well as devices. Your equipment will be damaged.
Applications
Used as a voltage regulator.
Use the stator of the square full cage induction motor as a starter to deliver 50 to 60% of the absolute full voltage.
Used in power transmission and distribution.
