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The capacitors used in single-phase capacitor motors have no
Dielectric medium
Polarity Marking
Voltage Rating
All of these
Polarity Marking
Capacitors used in single-phase induction motors operate on alternating current (AC) supplies. Since AC continuously reverses polarity every half-cycle, non-polarized capacitors (such as paper, polypropylene, or non-polar AC electrolytic capacitors) are required. Consequently, these capacitors have no polarity markings because they can be connected in either direction in the AC circuit.
Capacitors used in single-phase induction motors operate on alternating current (AC) supplies. Since AC continuously reverses polarity every half-cycle, non-polarized capacitors (such as paper, polypropylene, or non-polar AC electrolytic capacitors) are required. Consequently, these capacitors have no polarity markings because they can be connected in either direction in the AC circuit.
I_{aux} = \frac{V}{Z_{aux} - jXcтАЛ} тАФ current in auxiliary winding with series capacitor
\theta =$$\phi{main} - ╧Х{aux} тЙИ90┬░тАФ phase difference between winding currents
In a single-phase induction motor, a capacitor is connected in series with the auxiliary (starting) winding to create a phase shift (ideally near 90┬░) between the main winding current and the auxiliary winding current. This creates a rotating magnetic field necessary for developing starting torque. Because the supply voltage v(t)=VmтАЛsin(╧Йt) alternates polarity at mains frequency (50 Hz / 60 Hz), a polarized capacitor would suffer dielectric breakdown and potential explosion if used.
Motor capacitors must withstand bi-directional AC voltage variations, requiring non-polar construction.
Polarized capacitors (like standard DC electrolytic capacitors) short-circuit or explode when subjected to reverse voltage in an AC circuit.
All motor capacitors have dielectric media (e.g., paper, polypropylene, or oil) and explicit AC voltage ratings (e.g., 250V AC, 440V AC).
Can be connected in an AC circuit without concern for terminal orientation.
Provides high reliability and continuous AC voltage endurance without dielectric degradation.
Physically larger and more expensive per microfarad than DC polarized electrolytic capacitors.
Capacitor-start induction motors (e.g., pumps, compressors).
Capacitor-run motors (e.g., ceiling fans, air conditioners).
Option A is incorrect because every capacitor must have a dielectric medium (air, paper, polypropylene, etc.) to store energy electrostatically.
Option C is incorrect because all capacitors must have a defined AC Voltage Rating (WVAC) to prevent dielectric breakdown.
Option D is incorrect because options A and C are essential attributes of motor capacitors, whereas option B is correct.
B is correct тАФ Capacitors used in single-phase AC motors are non-polarized to handle alternating currents, so they do not feature polarity markings.
Always verify whether a capacitor is used in an AC or DC circuit: AC applications (like motor starting/running or power factor correction) exclusively require non-polarized capacitors with an AC RMS voltage rating.