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speed measurement of AC motors

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pandi_2u

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is there any sensors or other methods available to monitor the speed of AC motors.
i would like to control the speed of induction motors and universal motors in closed loop fashion. can anyone suggest some useful tips.

thanks in advance
 

BradtheRad

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A coil placed near the motor might pick up a sinewave by induction.

You might have to experiment with different types of coils (low vs. high inductance, containing iron vs. containing none, etc.).

You might have to try it in different locations (near windings, near an opening in the housing, etc.).
 

kak111

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Couple small dc-motor or spepper motor to measured motor axle
(now you have tachometer) and measure generated voltage .
It is function of rpm.

Fix screw in radial direction to axle, measure with proximity sensor
or with small , coil magnet inside , how many pulses it generate in 1 min. = rpm.

Clue small white or reflective piece radial in axle, and count pulses with reflective sensor.

Make a encoder plate with holes fix it to axle and count pulses with optical cap sensor

etc....etc...
 

andre_teprom

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Tachometer is only suitable when is possible to take measurement directily inside motor mechanism.
However, many times it is not accessible.

In this case, if motor have coupled reducer, an rottary shaft encoder must be used, due to low RPM property, wich could derail the cloed loop control.

+++
 

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