Harmonics can have several effects on transformer efficiency, both in power transformers and distribution transformers. Harmonics are non-sinusoidal waveforms that have frequencies that are multiples of the fundamental frequency. They can be introduced into the electrical system by non-linear loads such as power electronic devices (e.g., computers, variable speed drives, rectifiers, etc.).
Increased Copper Losses: Harmonics result in additional copper losses in the transformer windings. Copper losses are primarily due to the resistance of the transformer windings. The presence of harmonics increases the effective RMS current flowing through the windings, leading to higher copper losses.
Increased Core Losses: Harmonics can also cause higher core losses in the transformer's magnetic core. The core losses are related to the reversal of magnetic domains within the core material. Higher-frequency harmonics cause increased eddy current losses and hysteresis losses, reducing the transformer's overall efficiency.
Reduced Power Factor: Harmonics cause the displacement of voltage and current waveforms, leading to a distorted power factor. A lower power factor can result in increased apparent power in the transformer, requiring larger currents to deliver the same real power. This leads to higher losses in the transformer.
Overheating: Due to the increased losses caused by harmonics, the transformer may experience higher operating temperatures. This can result in accelerated aging of insulation materials and ultimately lead to a shorter transformer lifespan.
Voltage Distortion and Unbalanced Loading: Harmonics can cause voltage distortion in the supply system, affecting not only the transformer but also other connected equipment. Additionally, they may lead to unbalanced loading on the transformer and other parts of the electrical distribution system, further reducing the overall efficiency.
Resonance Issues: Harmonics can interact with the transformer's inherent impedance and capacitance to cause resonant conditions in the system. These resonance issues can lead to excessive currents, voltage fluctuations, and additional losses.
To mitigate the negative effects of harmonics on transformer efficiency, various measures can be taken, such as:
Installing harmonic filters to suppress specific harmonics and reduce their impact on the transformer and the electrical system.
Using low-harmonic or harmonic-free equipment to reduce the generation of harmonics at the source.
Designing transformers with special construction techniques and materials to handle harmonics more effectively.
Implementing proper power factor correction to reduce the impact of harmonics on the transformer's loading.
Overall, it's crucial to consider the presence of harmonics and their potential effects when designing, operating, and maintaining transformers to ensure optimal efficiency and reliability.