The GE IAC66K57A Time-overcurrent relay is a protective device used in electrical power systems.

It’s designed to detect excessive current and initiate a trip signal to a circuit breaker or other protective equipment.

Key features and characteristics:

1. Time-overcurrent protection: The relay operates based on the magnitude and duration of the current flowing through it. If the current exceeds a preset threshold for a specified time, the relay trips.

2. Inverse time characteristic: This means that the relay’s operating time decreases as the current increases. This allows for faster protection against short circuits while providing a delay for normal load variations.  

3. Adjustable settings: The relay’s current threshold and time delay can be adjusted to suit the specific requirements of the application.

4. Instantaneous overcurrent unit: Some models of the IAC66K57A relay also include an instantaneous overcurrent unit that provides immediate tripping for extremely high currents.  

5. Applications: The relay is commonly used for the protection of motors, feeders, transformers, and other electrical equipment.

Typical applications:

1. Motor protection: The relay can be used to protect motors from overload and short circuit conditions.

2. Feeder protection: It can be used to protect feeders against excessive current caused by faults or overloading.

3. Transformer protection: The relay can be used to protect transformers from overheating due to excessive current.