At no load, circulating current is given by the electrical phenomenon in which an alternating current (AC) flows through a transformer's primary winding and secondary winding, even when there is no external load connected to the secondary winding.
The Cause of Circulating Current
The main cause of circulating current is the leakage inductance of the transformer's windings. Leakage inductance occurs due to the magnetic flux that links the primary winding but does not link the secondary winding. This results in a voltage being induced in the secondary winding, even when there is no load connected.
How Circulating Current Affects Transformers
Circulating current can have a damaging effect on transformers. The current can generate heat, which can cause the transformer's insulation to deteriorate and eventually fail. The heat generated by the circulating current can also cause the windings to expand and contract, leading to mechanical stress and potential damage to the transformer.
Measuring Circulating Current
Measuring circulating current can be done by using a clamp-on ammeter. The ammeter is placed around one of the transformer's windings, and the current flowing through that winding can be measured. This method can be used to determine the amount of circulating current flowing through the transformer.
Reducing Circulating Current
Reducing circulating current is essential to prevent damage to transformers. One solution is to use a transformer with a lower leakage inductance. Another option is to use a transformer with a tertiary winding, which can help to divert the circulating current and reduce the amount that flows through the primary and secondary windings.
Conclusion
Circulating current is a common problem in transformers that can cause damage and reduce efficiency. Understanding the causes of circulating current and how to measure and reduce it can help to prolong the life of transformers and improve their performance.
