JPH0475453A - Induction motor - Google Patents

Abstract

PURPOSE:To realize simple and smooth speed control requiring no maintenance by winding first and second sets of stator windings coaxially around a set of stator core group and setting a phase difference between rotating fields produced, respectively, from the first and second stator windings. CONSTITUTION:When switches S1, S2, S3 are opened and a power switch S0 is closed, stator windings 11 and 10 are connected in delta with electrical phase difference of 60 deg.. When the switches S1, S2, S3 are closed subsequently, rotating fields of the stator windings 10, 11 have electrical phase difference of 0 deg.. When the switches S1, S2, S3 are closed gradually, intermediate torque characteristics having electrical phase difference between 60 deg. and 0 deg. can be obtained. According to the arrangement, only three wires are required for the wiring from power supply side to motor side if a switch is arranged on motor side, and the motor can be operated with high torque from low speed to high speed with low starting current.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a general induction motor, and more particularly, to an induction motor that can smoothly change speed from low speed to high speed with a simple and inexpensive device.

[Conventional technology]

In order to control the speed of an induction motor, the torque characteristics can be controlled proportionally by changing the secondary resistance of the induction motor through brushes, slip rings, etc., or by changing the voltage and current of the power supply on the negative side. There are those that control the speed, those that supply power to the primary side with an inverter and change the frequency to control the speed, and those that combine the above methods. Additionally, star-delta switching is used to suppress the current during startup, but this only works during startup.

[Problem to be solved by the invention]

Most of the speed control of induction motors as in the above conventional technology requires devices for voltage adjustment, current adjustment, and frequency adjustment, and these devices are expensive as devices other than electric motors, and special speed control is required. It will not be used unless it has a purpose. In addition, the conventional technology described above for changing the secondary resistance is a simple method of switching an external resistor via a slip ring, etc., but since there is a sliding part such as a slip ring, maintenance is required and continuous In order to change the secondary resistance, a liquid resistor is used as the secondary resistance, but this requires managing the liquid in the resistor and is only used in high-output wound induction motors. Furthermore, star-delta switching devices that take into consideration the starting current at startup are ones that act only at startup, as mentioned above, and cause a large shock because they momentarily cut off the load current when switching star-delta. . From the above, we can conclude that induction motors have the advantages of secondary resistance switching, which are simple and do not require maintenance, and the advantages of voltage, current, and frequency adjustment, which allow smooth speed control, and are inexpensive. The provision of such information is a technical challenge.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a stator in which two sets of stator windings, a first and a second, are wound concentrically around one stator core group, and It is constructed by a rotor provided concentrically, and a phase shift device that provides a phase difference between the rotating magnetic field generated by the first stator winding and the rotating magnetic field generated by the second stator winding. Further, the phase shift device connects the first and second windings at the same position in series, connects the entire windings in delta, and connects the connection point between the series windings at the same position and the other windings. It consists of an on/off switch that connects the connection point. Another phase shifting device has a second winding located at the same position as the first winding in series, and the entire winding is connected in delta, so that the phase difference between the rotating magnetic fields caused by the first and second windings is 00. A second on-off switch is constructed in which the first and second windings at other positions are connected in series and the entire windings are connected in delta, so that the phase difference between the rotating magnetic fields by the first and second windings is 1200. Consists of an on/off switch. The above open/close switch may use a variable resistor or a thyristor.

[For use]

The stator winding of the induction motor according to the present invention has a first stator winding and a second stator winding.
Two sets of stator windings connected to each phase of the power supply are connected in series, and the stator windings as a whole are connected in a delta shape. The first effect is that if two sets of stator windings are connected in series in each phase and the whole is connected in a delta shape, the current flowing through the first and second stator windings connected in series will necessarily be in phase. It becomes. Here, when the connection point of the arbitrary first and second stator windings and the connection point of the other first and second stator windings are respectively connected via on/off switches and the switches are closed, the stator The entire winding is star connected. In other words, the first and second stator windings are connected in parallel for each phase in a star configuration. This means that when the phase difference between the rotating magnetic field of the first stator winding and the rotating magnetic field of the second stator winding in the delta-shaped connection is an electrical angle c°, the connection point is When connected, the phase difference between the first rotating magnetic field and the second rotating magnetic field changes from the electrical angle of 0° to 60°. Conversely, when two sets of stator windings are connected in series in each phase in a delta shape, the rotating magnetic field of the first stator winding and the rotating magnetic field of the second stator winding are
If the wires are connected in advance so that the phase difference with the rotating magnetic field of the stator winding is 60 degrees electrical angle, then when connecting from a delta shape to a star shape as described above, the phase difference of the rotating magnetic field will be 60 degrees.
Changes from 0 to 0°. The fact that the phase difference between the rotating magnetic field of the first stator winding and the rotating magnetic field of the second stator winding is an electrical angle θ° means that it depends on the rotating magnetic field of the stator or the first and second stator windings. It is the sum of each rotating magnetic field. Also, as above, the phase difference is 600 electrical degrees, which means that the vectors of the rotating magnetic field of the first stator winding and the rotating magnetic field of the second stator winding are shifted by 60 degrees in electrical angle, and the fixed The child's rotating magnetic field is the vector sum of the first and second rotating magnetic fields. Now, as a second effect, the phase difference between the rotating magnetic field of the first stator winding and the rotating magnetic field of the second stator winding is 1 electrical angle.
The operation when both the open/close switch 1 connected so that the phase difference is 20 degrees and the open/close switch 2 similarly connected so that the phase difference is ao will be explained. At this time, the connection is such that, as described above, the open/close switches 1 and 2 each connect two sets of stator windings in series in each phase so that the entire structure is in a delta shape. First, when you close the open/close switch 1, the phase difference or electrical angle is 120
°Delta-like connection. Next, when the open/close switch 2 is closed, each phase is connected in series by the open/close switch 1.2, so the connection point of the first and second stator windings connected in series, that is, the open/close switches 1 and 2, is connected in series. The provided connection points are short-circuited by the on/off switches 1 and 2, and the first and second stator windings are connected in parallel for each phase in a star shape, and at the same time, the phase difference becomes 12 electrical degrees.
It changes from 0° to 600 electrical angles. Next, when the open/close switch 1 is opened, the phase difference changes to 0° electrical angle by the open/close switch 2. In this way, the phase difference between the open/close switches 1 and 2 is +2[1', 6[10,[
It changes to 10. When the phase difference changes, the vector sum of the first and second rotating magnetic fields also changes from small to large, and thereby the torque induced to the rotor side also changes from small to large. In both the first and second actions, although the phase difference changes by opening and closing the on-off switch, the load current is not cut off, and especially in the second action, the phase difference changes from 120 electrical degrees to 0 electrical degrees. During the change, even if the switch is opened or closed, one of the switches is in the on state, so the load current will not be cut off, even temporarily. By the way, when the on-off switch is formed of a variable resistor or a thyristor, the current flow due to the opening and closing of the switch changes gradually rather than abruptly, so not only is there no interruption of the load current, but the torque change due to the opening and closing of the switch is gradual, reducing the risk of shock. It is possible to change gears without any need. Opening/closing control of the opening/closing switch can be performed in various ways other than manual operation, such as control based on the rotational speed of the electric motor or timed control using a timer. In particular, if the opening/closing of each open/close switch is controlled by a timer, the configuration becomes as simple as turning on the main power, and it can be handled in the same way as a general induction motor. In addition, even if two strings of stator winding are wound, the entire winding is connected in series and connected in a delta shape, so if an on/off switch etc. is provided on the motor side, the power supply will be star delta if it is 3 phase. Unlike switching, only three wires are required.

[Embodiment] The present invention will be described with reference to an induction motor comprising one stator and a single rotor, and the rotor may be either a squirrel cage rotor or a wound rotor. Further, the present invention will be explained with a focus on the stator winding on the stator side. A connection diagram of the first stator winding, the second stator winding, and the open/close switch of the stator according to the first embodiment is shown first. One terminal of each coil of the first stator winding 11 (Ut
, V'+, W+) are connected to the power supplies R, S, and T via the power switchgear So, and the other terminals (Xl,
Yl, Z+) is connected to one terminal of the second stator winding 10 (
Y2, Z2, X2) and the other terminal (V2, W2) of the second stator winding 10.
, Y2) are connected to the terminals (U, .V, ,W,) in a delta connection. Also, the connection point between terminals X and Y2 of the windings connected in the same phase,
An open/close switch S1 is provided to connect the terminal Y1 of the other phase to the connection point of 22. An opening/closing switch S2 is provided to connect the connection point between the terminals Y1 and 22 of the other windings connected in the same phase and the connection point between the terminals Z1 and X2 of the other phase. Furthermore, the connection point between terminals z1 and X2 of the windings connected in the same phase, and the terminals X1 and Y of the other phase
An open/close switch S3 is provided to connect the two connection points. In this case, the open/close switches Sl, S2. When Sq is opened, the first stator winding 11 and the second stator winding 10 are connected such that the phase difference of their respective rotating magnetic fields is 60 degrees in electrical angle. For example, the windings v, -X and U2-X2 are mechanically arranged at the same position and with terminal symbols in the same direction. In addition, the on/off switches S+, S2, S, and the phase shift device 12
form. The operation of the above configuration will be explained. First, switch S
ll S2. When S3 is opened, the power switchgear S [1 is closed, the first stator winding 11 and the second stator winding 1
0 means a delta connection with a phase difference electrical angle of 600. This is shown in FIG. In other words, the shared voltage E of the coil Ul-Xi of the stator winding 11
1 and the shared voltages E, - of the coils u2-x2 of the corresponding windings 10 are connected so as to have an electrical phase difference of 60°. If the instantaneous value of the rotating magnetic field at this time is expressed as a vector, it will be as shown in Figure 3, and the rotating magnetic field a of the winding Ul-Xl and the winding U2-X
The rotating magnetic field a' of No. 2 has an electrical angle of 60°, and its composite vector is as follows. Then, when the switches s, s2°S3 of the transfer device 1-2 are closed, the phase difference between the rotating magnetic fields of the first stator winding 11 and the second stator winding 10 becomes 0° electrical angle. . The wiring connections at this time are shown in FIG. The instantaneous value of this is expressed as a vector as shown in Figure 5.The rotating magnetic field a of the winding Ul-Xl and the rotating magnetic field a- of the winding U2-X2 have an electrical angle of 0°, and their combined vector is as shown in A. This is the sum of the rotating magnetic fields a and a'. By the way, in this embodiment, the switches Sl and S of the phase shifter 12
2. S3 was closed at the same time, but if these open/close switches are gradually closed one by one, the rotating magnetic field becomes unbalanced, but an intermediate torque characteristic of 06 can be obtained from a phase difference electrical angle of 60°. Next, FIG. 6 shows a wiring diagram of the first stator winding, the second stator winding, and the on/off switch of the stator according to the second embodiment of the present invention. One terminal (U+,
Vl, Wt) are connected to the power supplies R, S,
At the same time, the other terminals (Xl, Y+, Z+) are connected to one terminal of the connection switch S4. Also, one terminal (U) of each coil of the second stator winding 10
2. V2. W2) is connected to the other terminal of the connection switch S1, and the first stator winding 11 and the second stator winding 10 are connected in series via the connection switch S4. The other terminals (X2, Y2, Z2) of each coil of the second stator winding 11 are connected so that the entire stator winding is delta connected. Also, one side of the connection on/off switch S5 is the connection on/off switch S.
The rotating magnetic field of the first stator winding 10 and the rotating magnetic field of the second stator winding 1-1 have an electrical phase difference of 1200 degrees. One of the stator windings 10 (U2.V2.W2) is connected in this way. Therefore, the connection opening/closing switch S4 connects each coil of the first stator winding 11 and each coil of the second stator winding at the same position in series, and connects the entire winding in delta, and Let the phase difference of the rotating magnetic field due to the windings be 0°. Further, the connection opening/closing switch S5 is connected to the first stator winding 11.
Each coil is connected in series with each coil of the second stator winding 10 located at another position, and the entire winding is connected in delta, so that the phase difference between the rotating magnetic fields caused by the first and second windings is 120°. do. In this embodiment, the connection on/off switches S4 and S5 form a phase shift device 13. The operation of the above configuration will be explained. First, when the connection switch Sa (hereinafter referred to as switch S4) is closed and the power switch SQ is closed, the first stator winding 11 and the second stator winding 10 are connected in series to form a delta connection. . This is shown in FIG. In other words, the coil U of the stator winding 11
1 to X1 and the coils U2 to X2 of the winding 10 are connected in series, and in this case, the phase difference between the shared voltages of both coils is Oo. The same applies to other phases. Subsequently, when the connection switch S5 (hereinafter referred to as switch S5) is closed, the phases of the switch S4 are short-circuited, so that the stator winding 11 and the stator winding 10 are star-connected. This is shown in FIG. A vector diagram of the shared voltage E1 of the coils U1-X1 and the shared voltage El- of the coils U2-X2 is as shown in FIG. 9, and the phase difference is switched to 60°. Next, when only the switch S4 is released, the voltages shared by each coil become as shown in FIG. 10, and as described above, the voltages shared by the windings 10 and 11 have a phase difference of 1200 between the stator windings. As described above, it is possible to provide a three-step phase difference by using the two connection open/close switches, switch S4 and switch S5. In addition, when the phase difference is 600, that is, when switches S4 and S5 are turned on, the phase of switch S4 is shorted by switch S5, so even if there is a short circuit due to other causes such as contact failure, the motor will burn out, etc. No accidents will occur. Further, a switch S4 for switching the phase is provided. Since one of the switches s5 is always in a closed state, there is no interruption of the load current due to the opening and closing of the switch. The vector diagram showing the instantaneous value of the rotating magnetic field at each phase difference is the same as that described in the first embodiment, and will therefore be omitted. The phase difference in each of the above embodiments is determined by switching the phase shift device 13 such that the phase difference is 120° at startup, 60° in the middle, and 00 during operation. Up to now, in addition to the phase shift device switch or connection switch for switching the phase difference, a variable resistor or a switch element such as a SIRISK may be used. In this case, the fundamental electrical phase difference between the first and second
However, if a switch element is used in place of the open/close switch, the torque characteristic is changed from the torque characteristic when the phase difference is 60 degrees electrical angle to the torque characteristic when the phase difference is 120 degrees electrical angle. come to have. This is because the on/off switch changes the connection state gradually instead of switching it all at once, and the wiring of the present invention allows the connection to be changed over time no matter which state the switch is open or closed.
In other words, this is possible because there is no electrical control over the opening and closing of the on-off switch, and there is no interruption of the load current. In addition, since it has an intermediate torque characteristic due to the use of a switch element, there is no sudden change in the generated torque that would cause a shock, and the speed can be controlled smoothly from startup to operation. FIG. 11 shows an example of the torque characteristics according to the first embodiment and the second embodiment. If a transfer device consisting of an open/close switch is provided on the motor side as shown in Figures 1 and 6, only three wires are needed from the power supply side to the motor, and the Y-△ It is possible to create an electric motor that has a small starting current and can be operated at high torque from low to high speeds without requiring complicated wiring for starting. Next, regarding an example in which a control device is incorporated into a phase shift device,
This will be explained with reference to FIGS. 12 and 13. First, in the configuration shown in FIG. 12, the induction motor 1 has a three-phase power supply 22 equipped with a switchgear.
It is connected to. In addition, the induction motor is integrally provided with a phase shift device 2o.
The phase shift device incorporates a sequence circuit control device 21 consisting of a timer. Next, the configuration shown in FIG. 13 will be explained. The induction motor 1 is connected to a three-phase power supply 22 equipped with a switchgear. Further, the induction motor is integrally provided with a phase shift device 20, and the phase shift device includes a sequence circuit control device 21 consisting of a timer.
Incorporate it. Next, the configuration shown in FIG. 13 will be explained. The induction motor 1 is connected to a three-phase power supply 22 equipped with a switchgear. Further, the induction motor is integrally provided with a phase shift device 20, and this phase shift device incorporates a control device 23 composed of a hard logic circuit, etc., and a speed detector 24 for detecting the speed of the motor. . Each of the control devices 21 and 23 controls opening and closing of the above-mentioned on-off switch of the phase shift device 20 based on a timer or a signal from the detector 24. [Effects] As described above, the induction motor of the present invention is a suitable motor when the purpose is to improve startability with constant torque characteristics or square-law low-speed torque characteristics, excluding equipment that always requires variable speed. be. Also, when wiring the motor, the phase shift device is integrated with the motor, so in the case of a three-phase power supply, the motor can be wired with three wires, and as long as the direction of rotation is not mistaken, anyone can wire the motor. . Furthermore, unlike star-delta starters, this is possible with only three wires, so equipment costs can be significantly reduced by downsizing the equipment surrounding the motor, such as piping materials for the wiring, and simplifying the associated work. It has become possible. Therefore, the use of induction motors that can diversify torque and smoothly increase speeds from low speeds to the rated speed range has expanded, and it is now possible to make an even greater contribution to all fields that require motors with improved maneuverability.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram showing the stator windings of the induction motor of the present invention, FIG. 2 is a wiring diagram at a phase difference of 600, FIG. 3 is a vector diagram of a rotating magnetic field at a phase difference of 600, and FIG. A connection diagram for a phase difference of 0°, FIG. 5 is a vector diagram of a rotating magnetic field at a phase difference of O0, FIG. 6 is a connection diagram showing a stator winding of another embodiment of the present invention, and FIG. 7 is a connection diagram for a phase difference of 0°. 8 is a connection diagram for a phase difference of 60°, FIG. 9 is a vector diagram of shared voltages for a phase difference of 6f10, and 1st
Figure 0 is a wiring diagram for a phase difference of 120°, 11th FI! J
12 is a control block diagram using a timer sequence, and FIG. 13 is a control block diagram using a logic circuit. DESCRIPTION OF SYMBOLS 10... Second stator winding, 11... First stator winding, 12... Phase shift device, 13... Phase shift device, 20
... Phase shift device, 21 ... Control section, 22 ... Power supply side, 23 ... Control section, 24 ... Speed detector.

Claims (4)

[Claims] (1) A stator in which two sets of stator windings, a first and a second, are concentrically wound around one set of stator core groups, and a rotor provided concentrically opposite to the stator. and a phase shift device that provides a phase difference between the rotating magnetic field generated by the stator winding and the rotating magnetic field generated by the second stator winding. (2) The induction motor according to claim (1), wherein the phase shift device connects the first and second windings at the same position in series, connects the entire windings in delta, and An induction motor characterized by comprising a winding at the same position and an on/off switch that connects a connection point between the windings and another connection point. (3) The induction motor according to claim (1), wherein the phase shift device connects the second winding at the same position as the first winding in series and connects the entire winding in delta. A first open/close switch that sets the phase difference of the rotating magnetic field caused by the winding to 0°, and the first and second windings located at other positions are connected in series, and the entire windings are connected in delta, and the first and second windings are connected in series. The phase difference of the rotating magnetic field due to the winding is 12
An induction motor comprising a second open/close switch that sets the angle to 0°. (4) The induction motor according to claim (2) or (3), wherein the opening/closing switch constituting the phase shift device is a variable resistor or a thyristor.