What is meant by motors in synchronous tie?
When the two slip-ring motors are required to run at the same speed, it is possible to do this by connecting their rotors together through the slip rings in conjunction with a single slip resistance. The starter for such a scheme includes a single rotor resistance, the last step of which is the continuously-rated slip resistance, and two-stator contactors, one for each motor. In order to limit the circulating current in the event of the motors being out of phase when started, a reactance is usually inserted in the interconnecting tie. The reactor is wound in two sections, and connected so that it is non-inductive to currents flowing through each half into the slip resistance but inductive to circulating currents between rotors. This reactance also assists load sharing when the two motors are driving a common load, as for example travel motors at opposite ends of an overhead crane. Fig. 36 – Connections of reversing-drum controller and three-phase slip-ring motor. The controller gives s
