A single-phase capacitor-start motor — an improved split-phase design. A capacitor in series with the start winding shifts its current almost 90° relative to the main winding's. The result is a nearly circular rotating field, so the starting torque is much higher than in a plain split-phase motor. Once up to speed a centrifugal switch drops the capacitor branch (in the capacitor-run variant it stays connected permanently, improving the power factor). Used where a high starting torque is needed: compressors, pumps, machine tools. The model shows the torque M, the capacitor voltage and the state of the start branch.
This page is a utility for simulating single-phase capacitor-start motor online with specified initial values.
Using the model. Close the switch to apply power — thanks to the capacitor the motor develops a high starting torque and runs up quickly, after which the centrifugal contact drops the start winding. Use the "supply voltage" slider and the series rheostat to set the supply and the inrush. The "load torque" slider sets the shaft load. The scopes show the voltage U(motor) and the current I(motor); compare the inrush with the split-phase motor — it is smoother here.
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