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Two-value Capacitor Induction Motor

  • Refer Figs. 6 and 7. The two-value capacitor motor combines the quiet operation and limited speed control advantages of a running permanent split capacitor with high starting torque of the capacitor start motor.

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  • Two capacitors (Fig. 6) are employed during the starting period. One of these, an electrolytic starting capacitor, similar to that used for the intermittent duty of the capacitor-start split-phase motor, is of fairly high capacity (about 10 to 15 times the value of the running capacitor) and is cut out of the circuit by a centrifugal switch when slip reaches about 25 per cent.
  • The major advantage of the two value capacitor motor is its high starting torque, coupler] with quiet operation and good running torque, Still classed as a reversing motor, when
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  • the line leads of one winding are reversed, it is reversed in the usual manner. When the speed drops below 25% slip during reversing, the centrifugal switch closes its starting contact, providing the maximum torque as the motor slows down and reverses. The contacts open again when the motor is up to 15% synchronous speed in the reverse direction. Frequent reversals, therefore will reduce the life of the centrifugal switch. For this reason, where frequent reversals are accomplished, permanent-split, single-value capacitor, using no centrifugal switch whatever, is preferable.

    Uses. This two-value capacitor motor finds use in smaller home air-conditioning units which use this motor in its compressor and operates on a 15 amp. branch circuit. The lower starting current and lower running current (7.5 amp. maximum) at an improved power factor over the capacitor-start motor, are obtained through the precise selection of starting and running capacitors for the fixed compressor load.