Because the wire ends are connected to the resistor and form a closed circuit, a current is developed in the loop (including the resistor), proportional to the induced voltage.Because the magnetic field is moving, it induces a voltage in the wire.The following lines describe what happens as a result: Rotation of the stator magnetic field is equivalent to moving the wire in a stationary field. The loop ends are fixed to the slip rings, and two brushes make the connection between the slip rings and the external circuit. Also, notice that the resistor is external to the wire loop and its connection to the wire loop is through slip rings that are mounted on the shaft holding the loop.įigure 1 One loop of rotor winding connected to outside circuit through slip rings. Notice that the single wire loop is connected to a resistor and together they form a closed loop. Three-Phase Wound Rotor Induction MotorĬonsider Figure 1 in which a one loop wire (for simplicity) is placed inside a rotating magnetic field. Another type is (squirrel) cage motor that has no wire winding and has no slip rings. The windings are accessible through slip rings. Wound rotor induction motor (WRIM): Type of induction motor for AC in which the rotor has wire winding. To withstand high currents, the rotor structure is modified and more resembles a cage than a winding. Squirrel cage induction motor: Type of alternating current induction motor in which the rotor winding has little resistance and thus carries very high current.
Also, for DC machines, there is only one commutator, but for AC machines there are two (for single phase) or three (for three-phase) rings. In both cases, they are isolated from their shafts. The difference between slip rings and commutators is that the former is made of one piece of metal, whereas the latter consists of many isolated pieces of metals around a ring. Remember that in DC machines we had brushes and commutators. They do not rotate and are connected to the outside circuitry. Slip rings are metallic circular rings mounted and rotating with the rotor shaft and connected to the rotor windings but insulated from the rotor body.īrushes are spring loaded to make good contact with the surface of the rings. The arrangement for windings on the rotor, which rotate, to be connected to outside circuitry that is stationary is done through slip rings. The windings must be connected to circuits outside of the rotor, though not to the three voltage lines. The rotor of the latter, however, as the name implies, has windings. The rotor of the squirrel cage motor has no winding, and there is no need for the rotor to be electrically connected to any electricity. One type is called Squirrel cage motor and the other is called wound rotor induction motor (WRIM).
The difference again comes from the structure of the rotor, and the two types are named based on the rotor structure. That is to say, in principle, one can interchange the stators of two similar (in size and power) synchronous and induction motor In this sense, the structure of the stator for a synchronous machine and an induction machine is the same, and only the rotors differ from each other. In other words, it lies in how the magnetic field in the rotor is made. Hence, one can say the difference between synchronous and induction machines lies in their rotors. This principle, together with the rotating magnetic field, constitutes the basis for the operation of induction motors and generators. The optimal prototype over all configurations was built and validated successfully against experimental data with a maximum error of 1.10%.Remember, also, that it is the relative motion between a wire and a magnetic field that counts that is to say, the wire can be stationary while the magnetic field moves.Īsynchronous motor: Another name for an induction motor. Based on the optimal design of Configuration 2, a blade trimming was applied, which allows to improve the initial efficiency by 7.86%. The Kriging and the EGO models predict with accuracy the objective functions of the optimal design with a maximum error of 4.50%. Configuration 2 allows to improve the efficiency by 7.64% and to reduce the force by 33.36% compared to Configuration 1. A coupling was achieved between CFD, Latin Hypercube Sampling, Kriging metamodel and the Efficient Global Optimization to find the optimal design.
The total efficiency and the force applied on the impeller are improved by maximizing and minimizing their values, respectively. Thirteen design parameters are selected for the trimming and in the impellers, blades and volute regions. In the present study, a powerful double-intake and rotor squirrel cage fan is designed and optimized by using a developed optimization process loop based only on open source libraries: Dakota, Salome and OpenFoam.
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