Most electrical appliances used in DIY or gardening work are powered by a universal motor, while the induction motor is only used for appliances requiring only moderate torque. Devices requiring rapid small-scale and low-power reciprocating movement (essentially pumps) often employ vibrators, derived from the principle of the electric bell. (Non-contractual photo, does not necessarily reflect the drawing)
It is a motor operating in both direct current and alternating current. It is characterized by a rotor and one stator made by stacking sheets of magnetic alloy, so as to eliminate the heating and vibrations that would cause the alternating current in homogeneous magnetic masses (induction of eddy currents).
The rotor and the stator comprise notches, in which there are windings. The protruding parts between the coils constitute the poles of the magnets created when the current flows through these coils.
The rotor has several coils, fed successively by the commutator blades which are in contact with the brushes.
The winding of the stator is connected in series with the rotor windings. On power-up, the brushes feed a pair of collector blades, which provide power to a rotor winding. This creates a magnet whose negative pole is attracted by the positive pole of the stator; the engine starts to spin. Turning, the collector causes a succession of feeds and cuts of the rotor windings, giving a rapid succession of attractions-repulsions between the poles of the rotor and those of the stator (several times per second).
It ensures, several times per second, the cut of the current arriving by the brushes. This results in the appearance of a spark between the "trailing" lip (that which is at the rear, in the direction of rotation) of each blade of the collector and the broom.
These sparks have two disadvantages: they induce electromagnetic waves that create noise for radio and television receivers; Moreover, they cause wear of the brushes and collector blades, resulting in a carbonaceous residue that can, in the long run, clog the insulating gap between two blades.
All commutator motors and brushes must therefore be suppressed, using a circuit having a small inductor and a capacitor; the latter can deteriorate and must be replaced as soon as the use of the motor causes parasites in the various receivers.
Attention, the suppression is obligatory.Be aware that if the motor used causes noise, you may be the subject of a complaint. In case of malfunction, it is usually sufficient to change the suppression capacitor.
It consists of a wound stator, but its rotor has no winding. This last element consists of a metal cylinder on the periphery of which the conductive rods are inserted into notches: it is a rotor "cage squirrel".
The conductive rods are inclined relative to the generatrices of the rotor, to reduce vibrations and noise.
This type of engine does not have a collector. Its operation is relatively silent and practically free of parasites. Furthermore, it does not require any maintenance, except for dust removal from time to time.
However, the induction motor has the disadvantage of providing only low torque and easily stall when the load on its axis increases abruptly. This is why it is never used in appliances that require a large torque (drills or clippers, for example).
It comprises an M-shaped laminar frame, surrounded by a coil, which attracts and pushes at the frequency of the current (that is to say 100 times per second) a movable magnet biased by a spring. This type of motor is only used for small pumps.
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