The Three-Phase Asynchronous Motor #
The most widely used motor in industry. A rotating magnetic field in the stator induces currents in the rotor, producing torque.
Synchronous Speed #
$$n_s = \frac{60 \cdot f}{p}$$At 50 Hz: 3000 rpm (1 pole pair), 1500 rpm (2 pole pairs), 1000 rpm (3 pole pairs).
Slip #
The rotor always turns slightly slower than the field: \(s = \frac{n_s - n}{n_s}\). Typical: 2-5%.
Key Specs #
Efficiency: 85-97%. Power factor: 0.7-0.9. Starting current: 5-8× nominal. Starting methods: star-delta, soft starter, inverter (variable frequency drive for speed control).
Applications #
Pumps, fans, conveyors, compressors, elevators, machine tools.
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