Rotation direction indicator for enclosed 3 phase motors - has star connected inductive pickup near motor stator winding

摘要

The rotational direction indicator circuit for three-phase motors is esp. useful in determining direction of rotation of totally-enclosed motors installed in appts. employed in unfavourable environments. A star-connected inductive pick-up coil (5) is placed in the vicinity of the motor stator windings. One phase of the pick-up coil is connected to earth. An adjustable arrangement of capacitors is connected in parallel across the phases for selection of resonant frequency of 1 kHz or 100 Hz. Each of the two-phase outputs are amplified in operational amplifiers, a transistor stage and output drive transformers. The transformers operate an indicator (7).