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Determine motor run capacitor value

Determine motor run capacitor value

Determine motor run capacitor value

(OP)
Mechanical engineer needs some help please.
I have a nice old iron centrifugal blower (circa 1958) and do not know what value run cap to use (no start cap). I have tryed a 2uF and the motor is very-very slow to run up to speed although as speed gets close to rated rpm the torque realy picks up. Trying an 8uF cap the motor runs up to speed in a few seconds but the motor sounds noisier compared to the 2uF run.
Spec.
230/250v 50Hz 1phase (same as my UK mains supply)
0.8 amp. Continuous rated. 2850rpm.
Type T.E (T.E ? I ask)
There are 3 terminals A B S (no others). The winding resistance over the terminals are AB=71.8   BS=74.3   SA=36.3 ohms.
I have connected cap across AB, Live to B, Neutral to S, to get it to start and run in the correct direction.

Is there a reasonably simple way to derermine the correct run cap value.
Dom.

 

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