Induction MotorAn induction motor is an alternating current-based electric motor, where the rotor's rotation frequency does not equal to the rotation frequency of the magnetic field generated by the stator's winding. The induction motor is in fact the most common type of electric motors. The induction motor has a stator and a rotor divided by air space. Its active elements are the winding and the magnetic core; the rest of the parts are structural designed to ensure the required hardness, rigidity, cooling and rotation capability. The motors used in household appliances are usually built with the help of a phase rotor and stator. But there also exist motors with a square-cage rotor, where the current at launch exceeds the rated current by 4-7 times. That's why only motors of 200 kWt and below can be directly connected to power supply.Today we will briefly cover some of such induction motors found in household appliances.A capacitor motor is an induction motor built to run on single-phase power. Its stator has two windings, one of which is connected directly to power supply, and the other - in series with an electric capacitor to generate a rotating magnetic field.Motors with starting elements are another type of induction motors. Here, the starting elements are represented by an increased resistance starting winding and a starting capacitor. Motors with increased resistance starting winding are simple in their construction and rather cheap. They come without an additional phase-shifting element. Motors with a starting capacitor are also very common. Here a starting capacitor is connected in series with a starting winding in order to improve the starting characteristics. Since the capacitor gets disconnected after start-up, the rest of the motor characteristics remain the same as those of the motor with an increased resistance starting winding. The connection of windings is peculiar in that the start-up uses a part of the main (operating) winding divided into two phases that are connected in series so, that the spatial shift angle of phase axes would constitute within 105-120°.During start-up one of the windings is bridged by the capacitor, which facilitates the required shift angle for current phases in the parts of the winding. After start-up the capacitor is disconnected by the same device, as the increased resistance starting winding. Under normal operation mode the motor operates as a regular single-phase motor with a pulsating field in the gap.The household induction motors often come with stator and rotor plates made of hot-rolled low-alloy steel and strip (coiled) cold-rolled low-texture steel. The motor shaft with frictionless bearings is regular (stepped) with shoulders for bearings. For friction bearings the shaft is made smooth.The type of bearings depends on the machine's operation mode, its durability and noise level requirements.The large number of various induction motors used in household appliances is a proof if their quality and operability in long cycles until complete wear. And this is proven by years of experience!
Loading...
3:48
quim barreirosby anfalz25,017,606 views
Link to this comment:
All Comments (0)