Asynchronous Capacitor Motor

(1) An asynchronous electric motor with single-phase mains, having two windings on its stator; one winding is connected directly to the power supply, and the other is connected in series with a capacitor to generate a rotating magnetic field. The capacitors cause a phase shift between the currents flowing through windings A and B (Figure 1), whose axes are spatially displaced. Maximum torque is developed when the phase shift between the two currents is 90° and the amplitude of the currents is selected such that the rotating field becomes circular.

To start an asychronous capacitor motor both capacitors (C₁ and C₂) are connected to the circuit; after the run-up, one capacitor (for example, C₁) is disconnected, since operation at rated speed requires considerably less capacitance than the startup. The start-up and operating characteristics of an asynchronous capacitor motor are close to those of a three-phase asychronous motor. Asynchronous capacitor motors are used in low-power electric drives; if the power rating exceeds 1 kilowatt

Figure 1. Circuit (a) and vector diagram (b) of an asynchronous capacitor motor:(U), (U_B), and (U_C) voltages; (I_A) and (I_B) currents; (A) and (B) stator windings; (S) centrifugal switch that disconnects capacitor C₁, after run-up of the motor; (C₁) and (C₂) capacitors

Figure 2. Diagram of connection of a three-phase asynchronous motor to a single-phase network: (a) star-connected stator windings, (b) delta-connected stator windings; (S₁) and (S₂) switches, (C_op) operating capacitor, (C_s) starting capacitor, (M) asynchronous electric motor

they are seldom used, because of the cost and size of the capacitors.

(2) A three-phase asynchronous electric motor, connected through a capacitor to single-phase mains. The operating capacitance of the capacitor for a three-phase motor is determined from the formula C_op= 2,800 (I/U) (microfarads) if the windings are star-connected and from the formula C_op = 4,800 (I/U) (microfarads) if the windings are delta-connected (Figure 2). The capacitance of the starting capacitor C_s is (2.5–3.0)C_op. The operating voltage of the capacitors must be 1.5 times that of the mains voltage; paper capacitors must be used.

单词	asynchronous capacitor motor
释义	Asynchronous Capacitor Motor Asynchronous Capacitor Motor (1) An asynchronous electric motor with single-phase mains, having two windings on its stator; one winding is connected directly to the power supply, and the other is connected in series with a capacitor to generate a rotating magnetic field. The capacitors cause a phase shift between the currents flowing through windings A and B (Figure 1), whose axes are spatially displaced. Maximum torque is developed when the phase shift between the two currents is 90° and the amplitude of the currents is selected such that the rotating field becomes circular. To start an asychronous capacitor motor both capacitors (C₁ and C₂) are connected to the circuit; after the run-up, one capacitor (for example, C₁) is disconnected, since operation at rated speed requires considerably less capacitance than the startup. The start-up and operating characteristics of an asynchronous capacitor motor are close to those of a three-phase asychronous motor. Asynchronous capacitor motors are used in low-power electric drives; if the power rating exceeds 1 kilowatt Figure 1. Circuit (a) and vector diagram (b) of an asynchronous capacitor motor:(U), (U_B), and (U_C) voltages; (I_A) and (I_B) currents; (A) and (B) stator windings; (S) centrifugal switch that disconnects capacitor C₁, after run-up of the motor; (C₁) and (C₂) capacitors Figure 2. Diagram of connection of a three-phase asynchronous motor to a single-phase network: (a) star-connected stator windings, (b) delta-connected stator windings; (S₁) and (S₂) switches, (C_op) operating capacitor, (C_s) starting capacitor, (M) asynchronous electric motor they are seldom used, because of the cost and size of the capacitors. (2) A three-phase asynchronous electric motor, connected through a capacitor to single-phase mains. The operating capacitance of the capacitor for a three-phase motor is determined from the formula C_op= 2,800 (I/U) (microfarads) if the windings are star-connected and from the formula C_op = 4,800 (I/U) (microfarads) if the windings are delta-connected (Figure 2). The capacitance of the starting capacitor C_s is (2.5–3.0)C_op. The operating voltage of the capacitors must be 1.5 times that of the mains voltage; paper capacitors must be used.
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