The Emerson CT SKC3400200 is a 3-phase AC Line Reactor (Mains Choke) designed for use with Control Techniques Unidrive, Commander, and Mentor MP drive systems. It is installed in the AC input line (or between the drive and motor) to protect the drive from power line disturbances, smooth current spikes, and reduce harmonic distortion. This reactor is crucial for applications with weak supply networks, long motor cable lengths, or multiple drives connected to the same bus.