The capacitor in the electric fan is not used for speed regulation but used to start the fan, called the starting capacitor.
Electric fans usually have only one capacitor, which is a pneumatic capacitor, because most fans are single-phase, and direct use of single-phase electricity can not generate a sufficient aerodynamic magnetic field, and can not maintain good operation, so this type of motor generally has two The windings are the main winding and the auxiliary winding.
The main winding is directly merged into the circuit, and the auxiliary winding is connected in series after the capacitor so that the auxiliary winding will have an angle difference.
The capacitor will play the role of shifting the phase to make the phase deviate. This is equivalent to obtaining two-phase electricity, and the phase is different, the rotor can be started, and then the main winding maintains the magnetic field to let it run, and the auxiliary winding continues to Push so that it does not stop due to external forces.
Generally speaking, household fans use unidirectional alternating current, which cannot generate a rotating magnetic field in the stator windings. In the two perpendicular pole windings, there is a set of capacitors connected in series to make the current lag 90 degrees, so that the two sets of stators The direction of the combined magnetic field of the coil begins to rotate, driving the rotor to rotate.
Magnetic field: After the stator conductor is energized, the alternating current forms a magnetic field in the stator due to the winding relationship. The magnetic field changes in height and position due to time.
Rotating magnetic field: The minimum need to have two sets of windings on the stator, they are 180 degrees different in position, one set is in the up and down position, and the other is in the left and right positions. If the two groups are supplied with alternating current, there is a phase difference between the alternating currents, and the rotating magnetic field It happened.
Rotating the conductor that cuts the rotor this time produces a conductor current, which has magnetism and electricity perpendicular to each other, then the rotor rotates according to the right-hand law.
Once the rotor is started, the rotating magnetic field is not so important, because the rotor is rotating due to inertia, the rotor conductor will also cut the magnetic field, there is a magnetic force, a bit of mutual hammer, the rotor continues to rotate according to the right-hand law.
Therefore, the rotation of the electric fan comes from the rotating magnetic field, and the rotating magnetic field comes from the power supply with a phase difference, but where does the power supply with phase difference come from? It is the function of the capacitor, which is important at startup and can be removed after startup. When the capacitor is not removed, the capacitor is used to optimize the power factor.
Next: What is a capacitor？