inductance problem ???

Question

Hello everyone.I am an electrician in Ireland, and came across a problem a few daysago.I was investigating why a motor of a washing machine in a commerciallaundry would not spin correctly and found the cables going from thetacho generator to the control electronic were causing the problem, Irerouted the cables and found all worked ok.I suspect some form of mutual inductance, the tacho cables only carrya small voltage, but was in a loom with many main voltage cables, Didanyone ever come across a similar problem ? If so what is the best wayof identifying the problem, would an oscilloscope be required. Eventhough I know I sorted out the problem I would like to know the bestway of testing for this problem .Thank you for all your helpSeamus

C What I Mean · Accepted Answer

You were most likely picking up induced noise from the higher voltagecables.  That noise is coupled into the tach signal and can make thefeedback signal erratic. To See it you would indeed need a scope.  You maybe able to read it on a meter as AC voltage.

Harry Bloomfield · Answer

| I strongly suspect it is not a mutual inductance problem. | It is a lot more likely that rerouting the cables either | cleared a short or disturbed a loose connection, allowing | the thing to work - for a while. |  | If it was a mutual inductance problem, it most likely | would have failed from day 1, and would be indicative of | a design defect.  On the other hand, vibration over time  | may have chafed the cable, creating a short, or  | loosened a connection somewhere. |  | I'll agree with that, except to add that assuming there were a mutual inductance problem....It would help if the two wires for the tacho generator could be made less susceptible to pickup, by twisting them together along their length.

inductance problem ???

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