Motor Principle
Stator rotating magnetic field generated by the principle of
Rotating magnetic field: magnetic field refers to the location of the axis of rotation with time of the magnetic field.
At three-phase asynchronous motor stator iron hearts of three groups to place the structure of identical windings U1U2, V1V2, W1W2, each phase winding at each worse Spaces 120 ° electric angle, to the three-phase windings in the access to symmetrical three-phase alternating current, stator and rotor in the air gap to produce a rotating magnetic field.
To the bipolar motor that 2p = 2 as an example, symmetrical three-phase windings U1U2, V1V2, W1W2 assumed to be concentrated winding, three-phase windings into a star then, and pass to three-phase symmetrical currents iA, iB, iC. Such as shown in Animation. Assumed that the current instantaneous value is positive when the windings are the first from the inflow side, the end of the outflow. Current inflow end with "×" that the current outflow end with "" express.
wt = 0 when, iA = 0;
iB is negative, that is, iB inflow from the end of V2, the first outflow of client V1;
iC is positive, that is, iC from the first side W1 inflow, outflow of the end of W2.
Current inflow end with "×" that the current outflow end with "" express.
The use of right-handed helix can be set to determine at wt = 0 instantaneous three-phase current generated by the synthesis of the magnetic field direction, such as animated demo shown.
Synthesis of the magnetic field can be seen are a pair of magnetic poles, magnetic field direction and the vertical axis line direction, the top is the Arctic, the Antarctic are below.
wt = π / 2 when, iA is positive maximum, that is, iA flows from the first end of U1, U2 outflow end;
iB is negative, that is, iB inflow from the end of V2, the first outflow of client V1;
iC is negative, that is, iC from W2 inflow, W1 outflow.
Synthesis of the magnetic field direction can be seen more time wt = 0 when the direction of the needle turned 90o.
Empathy can draw wt = π, wt = 3π / 2, wt = 2π when the synthetic magnetic field, we can see the magnetic field direction by clockwise rotation, a total turn 360o, that is, rotating the week.
To sum up, in the three-phase AC motor stator has the structure of the layout at the same spatial location of the difference between the angle of 120o electric three-phase windings, respectively, access to three-phase alternating current, the stator and rotor in the air generated by the synthesis stator magnetic field is along the inner circle of rotation, it said rotating magnetic field.
Of induction motor working principle said that it should be easy:
When the three stator windings to the symmetry through the three AC, it produced a synchronous speed n1 along the stator and rotor space for inner circle clockwise rotation of the rotating magnetic field. N1 because of rotating magnetic field in order to speed rotation, the start of the rotor conductors are stationary, it will be cutting the rotor conductors in the stator rotating magnetic field generated inductive electromotive force (EMF sensing the direction of right-hand rule used to determine). Derivation because of the conductors at both ends by a short circuit shorted ring, at the role of inductive electromotive force, the rotor conductors and inductive electromotive force will produce basically the same as the direction of the induced current. Rotor current-carrying conductor in the stator magnetic field by the electromagnetic force (the direction of force is determined to use his left hand set). Electromagnetic force on the rotor axis electromagnetic torque, rotor-driven rotating magnetic field along the direction of rotation.
Through the above analysis can be concluded from the motor working principle is: when the motor of the three stator windings (the difference between the 120 degrees angle of electricity), access to the three alternating current will produce a rotating magnetic field, the rotating magnetic field cutting rotor windings, which at the rotor Winding generated induced current (rotor winding pathway are closed), current-carrying conductor of the rotor at the stator rotating magnetic field will produce under the electromagnetic force, which formed in the motor electromagnetic torque shaft, the drive motor rotation, and motor rotation direction with the rotating magnetic field the same direction.
