What needs to be checked before paralleling two transformers?

When paralleling two transformers, it is crucial that their impedances are within a certain tolerance, typically + or - 10%. This is important because if the impedances of the transformers are too far apart, one transformer may take a disproportionate amount of the load, leading to inefficient operation and potential damage. Uniform impedance ensures that the load is shared evenly between the transformers, minimizing the risk of overheating and extending their lifespan.

While checking voltage ratings, polarity, and adhering to manufacturer's specifications are all important steps in the process, the requirement for impedance matching is particularly critical for the operational stability and safety of the parallel system. If the impedance values are not similar, even if other conditions such as voltage and polarity are suitable, the performance can be adversely affected.