JPS5922476B2 - Twin core wound induction motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wound induction motor, in which a starting resistor connected to a rotor winding is left as is in order to obtain high resistance torque characteristics at the time of starting, and the starting resistor is disconnected during operation after starting. The purpose of this invention is to provide a new induction motor that can obtain normal torque characteristics without any trouble.As a result, the present invention provides a maintenance-friendly motor that completely eliminates slip rings and brushes for starting resistance. It is possible to obtain an advantageous brushless type wound induction motor, or to omit a slip ring shorting switch even when a slip ring is used for the starting resistance.

As is well known, a starting method using an external secondary resistance is often used in wound induction motors.

This method is schematically illustrated in FIG. 1. In the figure, IM is a wound induction motor, and the rotor windings of each phase are connected to a slip ring SR. This slip ring SR
A starting resistor R and a short circuit switch SW are installed opposite to the starting resistor R and the short circuit switch SW. At the time of starting, a starting resistor R as an external secondary resistor is connected via the slip ring SR, and during operation after starting, the brushes are raised and the slip ring SR is short-circuited by a short-circuit switch. However, not only are the slip rings and brushes installed in rotating electric machines troublesome to maintain, but brush powder due to wear may cause deterioration of the insulation of the windings. It is troublesome because it has to be divided into sections. For this reason, there has recently been a demand for eliminating brushes in order to simplify maintenance, such as in brushless excitation systems for synchronous machines. In view of these points, the present invention relates to a wound induction motor that is started using a starting resistor, and in particular, normal torque characteristics can be obtained even when the starting resistor is connected to the rotor winding during operation, and therefore no slip ring is used. To obtain a novel induction motor that is advantageous and unprecedented, such as realizing a brushless electric motor or omitting a slip ring short-circuit switch even when an external starting resistor is installed via a slip ring. With the goal.

The purpose of this is to provide two sets of stator cores and rotor cores which are coaxially connected as twin cores according to the present invention, stator windings wound around each rotor core, and windings wound around each rotor core. The rotor winding is equipped with a rotor winding and the winding terminals are connected to each other for each phase, and a common starting resistor is inserted and connected between the winding terminals of each phase for each rotor winding. By supplying power to each stator winding, the electromotive force induced in each rotor winding is in phase with each other during startup, and the electromotive force is in opposite phase with each other during operation after startup. achieved. Next, the present invention will be explained in detail based on illustrated embodiments.

As shown in FIG. 2, the motor according to the invention is constructed as a twin core. That is, two sets of rotor cores 2A, 2B installed on the rotating shaft 1 and two sets of stator cores 3A, 3B facing the rotor cores 2A, 2B are provided. Each stator core 3A, 3B is wound with a stator winding 4A, 4B that receives power from a power supply, while the rotor core 2A,
Rotor windings 5A and 5B are wound around 2B. In particular, the rotor windings 5A, 5B are interconnected as shown in FIG. 3 or 4, and a common starting resistance ε is connected to each of the windings 5A, 5B. In the embodiment shown in FIG. 2, a common starting resistor 6 is provided on the rotating shaft 1 and is fixedly connected to the windings 5A and 5B without using a slip ring. This connection circuit is shown in Figure 3 or 4.
To explain the figure in more detail, the rotor windings 5A and 5B have winding terminals connected to each other via connection leads 7 for each phase. On the other hand, in the starting resistor 6, each resistor is connected in a star shape like the windings 5A and 5B, and this is inserted and connected between the connecting leads 7. In the above configuration, if the stator windings 4A and 4B are connected to the power supply circuit 8 so that the power is supplied to the stator windings 4A and 4B in the same phase when starting the motor, the rotor winding 5A , 5B also have the same phase, so that a current 1 s flows on the rotor winding side as shown.

That is, since the secondary current 1S passing through each winding 5A, 5B flows through the common starting resistor 6, an external secondary resistor is connected in series with each winding 5A, 5B, and high resistance torque characteristics are obtained. This high resistance torque characteristic is shown as a torque characteristic line Ts in the torque characteristic diagram of FIG. On the other hand, during operation after startup, as shown in Figure 4, one of the stator windings 4A and 4B is reversely connected to the power supply circuit 8 so that the power supply phase is shifted by 180 degrees with respect to the winding 4A. be done. As a result, the electromotive forces induced in the rotor windings 5A and 5B have opposite phases, and a current as shown in the diagram 1R flows across both the rotor windings 5A and 5B. This current 1R is generated even though the common starting resistor 6 remains connected.
This common starting resistor 6 is not passed through. Therefore, the starting resistance 6 is not added as a secondary resistance, and the torque characteristic at that time becomes the normal torque characteristic when no secondary resistance is added, as shown by the torque characteristic line TR in FIG. In addition, in FIG. 4, even if the common starting resistor 6 is disconnected from the circuit, there is no change in the flow of the current IR. As described above, starting with starting resistance and operation under load can be performed in the same way as a conventional wound induction motor.

However, the difference from the conventional method is that current flows through the starting resistor 6 only at the time of starting when voltages of the same phase are induced in the rotor windings 5A and 5B as shown in FIG. During operation with induced current, no current flows even though the connection remains. Therefore, the common starting resistor 6 does not need to be separated from the rotor winding even during operation after startup, and is installed on the rotating shaft and fixedly connected to the rotor winding as shown in Fig. 2 to implement the brushless system. It becomes possible to realize this. In addition, in order to switch and connect the stator winding 4B to the power supply circuit 8 from the time of startup to the time of operation as shown in FIGS. This is done by installing switches SW and SW2 and interlocking switching operations of each switch SW and SW2 according to the start and operation. In addition, a means for interposing a phase shifter between the stator winding 4B and the power supply circuit 8 and changing the phase of the power supply voltage via the phase shifter can also be adopted. Furthermore, as a mechanical means, the stator core 3B is configured to be able to move relative to the stator core 3A in the circumferential direction in FIG. The relative angle between and 3B is 1 in electrical angle
A method of relative movement such as shifting by 80 degrees can also be used. In the embodiment shown in FIG. 6, compared to the previously described embodiment shown in FIG. There is.

Although this embodiment is not a brushless system, as in the previous embodiment, current flows through the common starting resistor 6' only at the time of starting.
It doesn't flow when driving. Therefore, compared to the conventional electric motor shown in FIG. 1, there is an advantage that a shorting switch for shorting the slip ring during operation can be omitted. In addition, common starting resistance 65
Even if the brush is disconnected from the slip ring 9 during operation, there is no effect on the torque characteristics even if it remains connected.Therefore, the brush may be raised above the slip ring 9 or not. In addition, each of the above embodiments has been shown in which the rotor cores as twin cores are installed side by side on the same rotating shaft, but the configuration is not limited to this, and two single cores each having a different configuration may be used. The rotating shafts of the electric motors may be connected, the rotor windings may be interconnected, and a common starting resistance may be added.

As described above, according to the present invention, current flows through the common starting resistor connected to the rotor windings only at the time of starting and acts to provide high resistance torque characteristics. does not flow and does not act as a secondary resistance. Therefore, by installing the common starting resistor together with the rotor winding on the rotor side and fixedly connecting the two, it is possible to realize a brushless system that is advantageous in terms of maintenance. Alternatively, even when the common starting resistance is connected as an external resistance outside the machine via a slip ring, the short-circuit switch of the slip ring can be omitted, providing an advantageous and novel twin-core wound induction motor that has never existed before. can do.

[Brief explanation of drawings]

Figure 1 is a schematic circuit diagram of a conventional wound induction motor.
FIG. 2 is a configuration diagram of an electric motor based on an embodiment of the present invention, and FIG.
4 and 4 are connection diagrams of an embodiment of the present invention showing current distribution at startup and operation, FIG. 5 is a connection diagram of a rotor winding equipped with a starting and operation changeover switch, and FIG. FIG. 7, which is a schematic diagram showing another embodiment of the invention, is a torque characteristic diagram for explaining the operation. 1: Rotating shaft, 2A, 2B: Rotor core, 3A, 3B: Stator core, 4A, 4B: Stator winding, 5A, 5B: Rotor winding, 6, 6': Common starting resistance, 7: Connection lead between rotor windings, 8: Power supply circuit, 9: Slip ring, I
s: Current during starting, IR: Current during operation, Ts: Torque characteristics during starting, TR: Torque characteristics during operation.

Claims (1)

[Claims] 1. Two sets of stator cores and rotor cores that are coaxially connected as twin cores, stator windings wound around each stator core, and windings wound around each rotor core and each phase Each rotor winding has a rotor winding whose winding terminals are connected to each other, and a common starting resistor which is connected between the terminals of each phase for each rotor winding. A twin core winding system characterized by supplying power to each stator winding so that the electromotive forces induced in the child windings are in the same phase, and the electromotive forces are in opposite phases during operation after startup. induction motor.