Transformers should not be connected to circuits exceeding what percentage above the nameplate rating?

Transformers are designed with specific voltage and current ratings, known as nameplate ratings, that indicate their optimal operating conditions. Operating a transformer beyond its rated capacity can lead to overheating, reduced efficiency, and potential failure.

The correct percentage limit for connecting transformers to circuits is 5% above the nameplate rating. This strict limit helps ensure that the transformer does not exceed its thermal limits. Operating at or below this threshold allows the transformer to maintain its performance and reliability, thereby prolonging its service life and ensuring safety. Exceeding this limit can cause insulation breakdown and other issues that compromise the device's functionality.

In contrast, higher percentage limits like 10%, 15%, or 20% increase the risk of damage and operational inefficiency, making them unsuitable options. Therefore, maintaining a strict adherence to the 5% guideline is vital for the safe and reliable operation of transformers in electrical systems.