What device compares the input voltage for phase angle, voltage magnitude, and frequency?

The device that compares input voltage for phase angle, voltage magnitude, and frequency is the synchronizing monitor. This tool is instrumental when it comes to ensuring that two or more electrical sources are in alignment before they are connected to a common bus or electrical network.

The synchronizing monitor evaluates phase displacement, voltage levels, and frequency, providing visual and auditory signals to indicate when the conditions for synchronization are met. This is critical in power systems, as synchronization helps prevent damage to equipment and ensures the stability of the electrical grid.

In contrast, other devices listed do not serve the same comprehensive purpose. While a voltage relay might protect circuits by disconnecting them under certain conditions or voltage levels, it does not analyze phase angle or frequency in the same way. A power analyzer primarily measures and records various electrical parameters but does not focus on synchronization. The phase comparator, while it can compare phases between signals, is generally more limited in scope compared to the functionalities of a synchronizing monitor.