The reason for the start cap is to create a close as possible 90° phase shift (L - C) in the start winding, if just a start winding, I doubt it is close to 90° but probably enough to get the initial spin & direction.. Sure a start capacitor increases starting torque, but may increase initial amp draw, makes sense as the cap needs to charge up, so maybe just making a bigger electrical hole to dump current into.
Do you think adding any value of start capacitor would lower current inrush?The reason for the start cap is to create a close as possible 90° phase shift (L - C) in the start winding, if just a start winding, I doubt it is close to 90° but probably enough to get the initial spin & direction.
Pump maker left it off to save money, as it is not really needed, but it was not optimal for every situation, like running off an inverter, I mean who does that, hah! Me.The reason is the sooner it comes up to speed, the lower the current, so the closer the phase shift angle in the start winding is to 90° the more efficient the start cycle/period.
The LC combination of the start winding and the cap value provides this phase angle difference.
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by Lianne Frith