2, of single-phase AC motor rotate principle
Single-phase AC motor has a winding only, rotor is squirrel-cage. When single-phase sine electric current passes stator winding, electromotor is handed in with respect to meeting generation change magnetic field, the rule of sine of the intercrop when losing by force to be followed with direction of this magnetic field changes, but be fixed on dimensional azimuth, weighing this magnetic field again so is to hand in become pulsatile magnetic field. This is handed in become pulsatile magnetic field is dissoluble it is two to be contrary whirl with each other of identical rotate speed, direction of rotation magnetic field, when rotor is dormant, these two rotate magnetic field generates two volume in rotor the torsion with equal, opposite way, make synthetic torsion is 0, so electromotor cannot rotate. When making with outside force when us electromotor rotates to some direction (rotate like the clockwise) , at this moment rotor and the whirl that arrange hour hand direction of rotation the decrescent of motion of cut lines of force between magnetic field; The whirl of rotor and anticlockwise direction of rotation the motion of cut lines of force between magnetic field greatens. Such balances were broken, the total electromagnetism torsion that rotor place produces will be no longer 0, rotor general down drive direction to rotate.

3. The principle of synchronous electromotor

Synchronous electromotor is to belong to alternating current machine, stator winding and asynchronous electromotor are identical. Rotate speed coming back spends its rotor to arise with stator winding place rotate the speed of magnetic field is same, call synchronous electromotor so. as a result of such, the electric current of synchronous electromotor is in phasic going up is lead at voltage, namely synchronous electromotor is a load that allow a gender. For this, in a lot of moment, synchronous electromotor is the power element that in order to improves power supply system.
Synchronous electromotor has two kinds roughly on the structure:
1, rotor undertakes excitation with dc. The rotor of this kind of electromotor is shown 1 times like the graph, can see from inside the graph, its rotor make it is shown extremely of type, installation is in the magnetic field coil above magnetic pole core is mutual series connection, receive have alternant and contrary polarity, two down-lead join outfit above two slip ring on the axis. Magnetic field coil is by small-sized dc dynamo or accumulator come incentive, in most synchronous electromotor, dc dynamo is to install what go up in electromotor axis, in order to supplies the excitation electricity of coil of rotor magnetic pole.
Because this kind of synchronous electromotor cannot be started automatically, still serve as what electromotor starts of squirrel-cage winding to use on rotor so. Squirrel cage winding puts in rotor all round, structure and asynchronous electromotor are similar.
Should connect in stator winding on when three-phase alternating current source, one arose to rotate inside electromotor magnetic field, lines of force of cut of squirrel cage winding and generation is faradic, make electromotor rotates thereby. After electromotor rotates, its speed slowly heighten arrives a bit under rotate the rotate speed of magnetic field, right now dc of by of coil of rotor magnetic field comes incentive, make certain magnetic pole is formed above rotor, these magnetic pole dog with respect to the purpose the whirl on stator magnetic pole, the rate that raises electromotor rotor so till with rotate till magnetic field synchronism rotates.
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