Motor Turn Stall Detector

In single segment AC induction motors, incessantly used in fridges and washers, a begin winding is used throughout the starting section. When the motor has reached a undeniable pace, this winding is fliped off once more. The begin winding is moderately out of segment to the run winding. The motor will best start turning when the present via this winding is out of section to that of the run winding. The phase distinction is in most cases provided with the aid of putting a capacitor of a couple of µF in series with the beginning winding. When the motor reaches a minimal pace, a centrifugal swap turns off the beginning winding. 

The circuit diagram doesn’t show a centrifugal switch; as an alternative it has a triac that's fliped on throughout the staring segment. For clarity, the sequence capacitor isn’t shown within the diagram. Once the motor flips it's going to proceed to do so so lengthy as it isn’t loaded an extreme amount of. When it has to force too heavy a load it'll virtually indisputably stall. A large current starts to waft (as the motor not generates a again EMF), which is restricted only by the resistance of the winding. This lead tos the motor to overheat after a undeniable time and result ins permanent damage. It is due to this reality essential to give you the option to observe when the motor turns, which happens to be extraordinarily easy. When the motor is popping and the start winding will no lengthyer be used, the rotation set offs a voltage on this winding.

Circuit diagram:

Motor Turn Stall Detector Circuit Diagram

This voltage will likely be out of phase since the winding is in a unique position to the run winding. When the motor ceases fliping this voltage is no longer affected and shall be in phase with the principles voltage. The graph presentations one of the relevant waveforms. More data may additionally be discovered within the utility no lengthyere for the AN2149 made through Motorola, which can additionally be downloaded from their site at www.motorola.com. We assume this accommodates some useful ideas, however keep in mind that the circuit exhibitn is only partially completed. As it stands, it for sure can’t be put straight to use. We should also draw your attention to the truth that primarys voltages can be lethal, so take great care when the primarys is connected!

Author: Karel Walraven - Copyright: Elektor July-August 2004