Which transformer is most appropriate for series street lighting applications?

In series street lighting applications, a constant-current transformer is most appropriate because it is designed to deliver a fixed amount of current to the connected load. This is essential for street lighting because it ensures that all lamps receive the same current, which is crucial for maintaining consistent brightness and performance across multiple lights that are wired in series.

With street lighting, where several fixtures might be connected in a single run, variations in voltage can occur due to differences in the fixture load or the length of the wiring. A constant-current transformer automatically adjusts the output voltage to maintain the desired current level, even when the total load changes. This ensures that lamps operate effectively without being underpowered or overpowered, which can lead to premature failure.

Other transformer types are less suited for this specific application. For instance, step-up and step-down transformers are used primarily for voltage adjustment rather than maintaining current, which is a critical factor in the operation of series lighting. Isolation transformers serve to separate different parts of an electrical system and reduce noise or provide safety, but they do not specifically maintain a consistent current for the connected loads in the way that constant-current transformers do.