JP2707924B2 - Two-stator three-phase cage induction motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has two rotor cores and two stators mounted on the same rotating shaft, and two stators are formed around a rotor conductor facing the rotor core. The present invention relates to a two-stator induction motor capable of generating a phase difference between rotating magnetic fields, and particularly to a phase switching device thereof.

[0002]

2. Description of the Related Art An induction motor having a plurality of stators is already known from Japanese Patent Application Laid-Open Nos. 49-86807, 54-29005, and 2-27920. These multi-stator induction motors attempt to perform torque control or speed control by providing a phase difference between stator windings to cause a shift in a rotating magnetic field generated around the rotor. . As a method of changing the phase difference, a mechanical method is used in which a plurality of stators are relatively rotated to provide a phase difference, and an electrical method in which the connection of the stator windings is changed to several types. May be provided.

[0003] The above-mentioned methods are based on various methods depending on the load or application, such as when the torque and speed of the induction motor are freely changed to cope with the load, when the speed at the start is smoothly increased, and the like. Will be used.

[0004]

SUMMARY OF THE INVENTION The present invention responds to a load by providing several types of gradual phase changes, and can be said to be an electrical method when distinguished by the above-mentioned prior art. The electric technique in the prior art is performed by switching the connection of the stator winding, and the phase difference is 0 °, 60 ° in electrical angle.
Although {120} and {180} can be implemented, the number of switches required for the switching is as large as dozens, and the device is expensive.

Further, there is a general induction motor provided with a star-delta switching device for the purpose of improving the startability. This is because the wiring is complicated in spite of a single stator, torque fluctuation occurs due to temporary disconnection of the load current at the time of star delta switching, and furthermore, the load current after the switching suddenly changes. The shock due to the increase and the sudden fluctuation of the generated torque was inevitable. FIG. 12 shows a torque characteristic curve obtained by the conventional star-delta switching.

The present invention has a torque characteristic at each phase difference obtained by switching the connection obtained by the above-mentioned prior art, but also minimizes the total number of switches required for switching, and realizes a load current by switching the switches. It is an object of the present invention to provide a two-stator induction motor having an inexpensive phase switching device with little increase in load current and little fluctuation in load torque before and after switching without disconnection.

[0007]

According to the present invention, there are provided first and second rotor cores which are axially mounted on the same rotation axis with a space or a non-magnetic member interposed therebetween. A cage-shaped integral cage rotor in which a plurality of conductors communicating with a two-rotor core are mounted on an outer peripheral portion of the rotor core, and a first stator opposed to each of the rotor cores; A core and a second stator core are provided around the first stator core and wound around the first stator core.
A stator winding and a second stator winding wound around the second stator core are configured to determine a phase of a rotating magnetic field of the first stator winding and a phase of a rotating magnetic field of the second stator winding. A first stator and a second stator connected in series delta so as to generate a predetermined phase difference between the first stator and the second stator, and a series of arbitrary phases of respective stator windings of the first stator and the second stator. The first stator winding comprises a switch provided between a connection midpoint and another two-phase series connection midpoint, and closing the switch while energizing each of the stator windings. A wire and the second stator winding are switched from a series delta connection to a parallel star connection so that the first stator has a rotating magnetic field generated around a first rotor core opposed thereto and the second stator has a rotating magnetic field. The phase difference between this and the rotating magnetic field generated around the second rotor core is determined from a predetermined phase difference at the time of startup. A phase switching device for reducing the electrical angle, the phase switching device for controlling the opening and closing of the switches of the control device and a secondary stator three-phase squirrel cage induction motor and having a is provided.

[0008]

According to the stator winding of the present invention, the connection method at the time of starting is as follows.
It is a series delta connection that produces an electrical phase difference due to the winding connections. At this time, the phase difference due to the connection of the windings is 180.
{120} or 60}. A short-circuit switch for short-circuiting a series connection midpoint of an arbitrary phase of the stator windings connected in this way and another two-phase series connection midpoint is provided. For example, a first short-circuit switch that short-circuits a certain series connection midpoint and a second short-circuit switch that short-circuits another series connection midpoint are provided. The first short-circuit switch
When the switch is closed, only a part of the lines is short-circuited, so that the winding connection becomes unbalanced. When the second short-circuit switch is further closed, the connection is switched to the parallel star connection. Therefore, at the time of start-up, it is a series delta connection having an arbitrary phase difference, and when the first switch is turned on, an unbalanced connection is made, and when the second switch is turned on, a parallel star connection with another phase difference different from the phase difference of the series delta connection is made. Is switched. That is, the serial delta connection provided with the electrical phase difference is switched to the parallel star connection, and at the same time the phase difference is switched. Specifically, when the short-circuit switch is closed from the serial delta connection and switched to the parallel star connection, the respective phase differences become 180 ° →
120 °, 120 ° → 60 °, 60 ° → 0 °.

In summary, the operation is as follows. First, when the power is turned on, the motor starts up in a series delta connection in which the phase difference between the stators is the arbitrary phase difference. The load is activated by the torque characteristic curve with an arbitrary phase difference. Next, after an elapse of an arbitrary time or at an arbitrary rotational speed, the second short-circuit switch is kept open while the first short-circuit switch is turned on to change the torque to unbalanced torque. In the unbalanced winding, a part of the shared voltage increases, and the torque increases by the increase of the shared voltage. Therefore, the load is further accelerated by the torque characteristic of the unbalanced winding, and the rotation of the motor increases.
Finally, when an arbitrary time has elapsed since the first short-circuit switch was turned on or when an arbitrary number of revolutions has been reached, when the second short-circuit switch is turned on, the parallel star having a phase difference of 60 ° less than the phase difference of the series delta connection. The load is driven by the torque characteristics of the connection.

[0010]

As described above, the phase difference and the torque characteristic can be changed in three stages simply by opening and closing only the first and second two short-circuit switches, and the number of contacts can be made far smaller than in the prior art. Further, as described above, since the start is made by the series delta connection and the first and second short-circuit switches are turned on or opened, the first and second short-circuit switches are directly connected to the start current. A large current does not flow, and the contact capacitance of the first and second switches can be reduced. Moreover, since the first and second short-circuit switches short-circuit or open only the midpoint of the series connection between the windings, the load current is not interrupted during operation, and the generated torque is instantaneously reduced to zero by switching the connection. It will not be. Furthermore, since there is a stage in which both the first and second short-circuit switches are turned on and used, even if one or both of the switches remain turned on due to an accident of the open / close switch, for example, welding of contacts, etc. It does not lead to the occurrence of electrical accidents. Even if the first and second short-circuit switches are in a short-circuit state, the connection of the stator windings is merely a parallel star connection, and there is no particular problem in the operation of the motor itself.

When the induction motor of the present invention is connected to a power source,
The number of wires required for connecting the phase switching device including the first and second short-circuit switches requires three power supply lines and four wires for the phase switching device, that is, seven wires in total. When the phase switching device is provided on the power supply side, seven wirings are required from the motor side and three wirings are required from the power supply side, and it is difficult to deal with on-site. Here, by integrating the phase switching device with the electric motor, three wires from the power supply side are sufficient. If the size of a general motor becomes large, the work of wiring six wires for starting the star delta becomes complicated. However, the present invention changes the torque characteristics of the induction motor by a phase switch device using two switches, and Is integrated with the induction motor, so that the number of wires is only three of the power supply lines. Therefore, even if the motor becomes large, it is only necessary to check the three wirings and the rotation direction of the power supply as in the case of a small motor, so that the cost of wiring materials can be reduced and the work can be simplified.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the two-stator three-phase squirrel-cage induction motor of the present invention will be described below.

The present applicant has already filed Japanese Patent Application No. 61-1283.
No. 14 (Japanese Patent Publication No. 2-27920) describes in detail the configuration and operation of an induction motor including a plurality of stators, which is a part of the configuration of the present invention.

Referring to FIG. 1, an embodiment of a motor forming a part of the structure of the present invention will be described. Reference numeral 1 denotes a two- stator induction motor according to the present invention, and the induction motor 1 has the following general configuration. Rotor core made of magnetic material 2,
3 is mounted on the rotor shaft 4 at an arbitrary interval. A non-magnetic core 5 is interposed between the rotor cores 2 and 3 or a space is provided between them. A plurality of conductors 6 mounted on rotor cores 2 and 3
Are connected to the rotor cores 2 and 3 to form an integral rotor 7, and both ends of the plurality of conductors 6 connected in series are short-circuited by short-circuit rings 8 and 8.

Although the conductors 6 provided on the rotor 7 are not short-circuited, only a part of the conductors 6 may be short-circuited by the resistance material 9 due to a difference in load characteristics to be connected.

A first stator 12 and a second stator 13 provided with windings 10 and 11 on outer portions facing the rotor cores 2 and 3 are arranged side by side on a machine frame 14 and fixed.

The connection between the windings 10 and 11 of the first stator 12 and the second stator 13 is, for example, a series delta connection which generates an electrical phase difference of 60 °.

Next, an embodiment of the induction motor of the present invention is shown in FIGS. FIG. 2 is a connection diagram of the induction motor of the present invention. One terminal (U) of each coil of the stator winding 11
₁ , V ₁ , W ₁ ) via power switchgear S ₀ to power A,
B, C, and the other terminal (X ₁ , Y ₁ , Z
₁ ) is connected to one terminal (Y ₂ , Z ₂ ,
X ₂ ) and the other terminals (V ₂ , W ₂ , U ₂ ) of the stator winding 10 are connected to the terminals (U ₁ , V ₁ ,
W ₁ ) is connected to a power supply so as to form a series delta connection. _One of the short-circuit switches S ₁ is connected to the other terminal X ₁ of the stator winding 11, and the other is connected to one terminal Z ₂ of the stator winding 10. The short-circuit switch S ₂ is coupled to one terminal X ₂ of the other terminal Y ₁ and the stator windings 10 of the stator winding 11.

The operation of the above configuration will be described. First, closing the power switching device S ₀ with open short switches S _1, S _2, a series delta connection having 60 ° electrical phase difference between the stator windings 10 and the stator windings 11.
This is shown in FIG. That is, the coil U of the stator winding 11
₁ shared voltage of to X ₁ of the divided voltage coil _U 2 to X ₂ of _{E 1} and winding 10 corresponding to _{E 1} 'is are then connected so as to have a 60 ° electrical phase difference. At this time, the shared voltage of each coil is の of the power supply voltage _Eab . The same applies to other phases.

Subsequently, a short-circuit switch S ₁ (hereinafter referred to as a switch S)
When ₁ to) close, terminal Z ₂ terminals X ₁ and the stator windings 10 of the stator winding 11 is shorted, the series delta connection becomes unbalanced. This is shown in FIG.

When unbalanced, a part of the winding (V _{2 to} Y ₂ ,
V ₁ to Y ₁₎ becomes parallel, divided voltage of the coil other than the line CA is increased. When the shared voltage increases, the generated torque also increases. The torque characteristic obtained at this time indicates an intermediate torque characteristic between the serial delta connection and the parallel star connection described below. The increase of the shared voltage at this time is similar to a voltage increase of the parallel star connection described later.

[0023] Figure 4-B is shorted to interline for easy understanding of the connection diagram of FIG. 4-A, i.e. it is a rewrite about the switch S _1. Next, when the short-circuit switch S ₂ (hereinafter, switch S ₂ ) is closed with the switch S ₁ kept closed, the phase difference becomes a parallel star connection with an electrical angle of 0 ° as described above. FIG. 5 shows the connection state at this time.

The shared voltage of the coils U _{1 to} X ₁ is E ₁ ,
When the E _ab and the line voltage of the power source, the magnitude of _{E 1} has a 2 / √3 = 1.15 times that of the series delta connection. Although this voltage rise is within the allowable range of the power supply voltage fluctuation, there is no problem. However, this voltage should be designed as the rated voltage of the coil. In addition, an increase in voltage has an advantage that torque characteristics are improved.

As described above, the switches S ₁ and S ₂
With these two short-circuit switches, three stages of torque characteristics can be provided. In other words, FIG. 6 shows the torque characteristics for starting the series delta connection, for the medium speed connection in the unbalanced connection, and for operating the parallel star connection.

As described in Japanese Patent Application No. 61-128314, the torque / speed characteristics when there is no communication resistance 9 are as follows. Although it is lower than in the case where it is provided, it is advantageous for a load having a square reduction characteristic, and a resistance material may be provided in a part depending on the load characteristic. Also, the phase difference 0
゜, that is, when the switches S ₁ , S ₂ are closed, the other (X ₁ , Y ₁ , Z ₁ ) of the stator winding 11 and one of the stator windings 10 (X ₂ , Y ₂ , Z ₁ ). ₂ ) is in a short-circuit state, and even if a short-circuit occurs due to a contact failure or other causes, an electric accident such as burnout of the motor does not occur.

Further, switches S ₁ ,
Closing of S _2, it never temporarily load current for opening and closing from a short circuit between the lines during operation due to the series delta connection is cut off, and inter-electrode voltage is at half the supply voltage For this reason, it is possible to use a small connection / opening switch having a small electric capacity, and to reduce the size of the phase switching device using the switches S ₁ and S ₂ .

By the way phase switching device and the switch _S 1 consisting as shunt switch _S 1, _{S 2} shown in FIG. 2,
The provision of control device for controlling the opening and closing of the S ₂ to the electric motor side, good in three wiring to the motor present from the power source side, a complex wiring for general large electric motor such as found star-delta starting of It is possible to provide an electric motor that can be operated at a high torque from a low speed to a high speed without need.

Next, the control of the phase switching device will be described with reference to FIG.
This will be described with reference to FIG. First, in the configuration of FIG. 7, the induction motor 1 is connected to a three-phase power supply 22 having a switching device. Further, a phase switching device 20 is provided integrally with the induction motor, and a control device 21 incorporating a sequence circuit including a timer is connected to the phase switching device. Next, the configuration of FIG. 8 will be described. The induction motor 1 is connected to a three-phase power supply 22 having a switching device. The induction motor is integrally provided with a phase switching device 20. The phase switching device is connected to a control device 23 composed of a hard logic circuit or the like, and the control device 23 detects the speed of the motor. The signal of the speed detector 24 to be performed is connected.

The above operation will be described. Each of the control devices 21 and 23 is provided with a timed or speed detector 2 by a timer.
4 and the first and second signals of the phase switching device 20 described above.
Open / close control of the short-circuit switch. For example, in the case of the control device 21, a general star delta start is about 1 standard.
Since the switching is performed in 0 seconds, the operation is started with a phase difference of 60 ° and the switching to the steady operation with the phase difference of 0 ° is performed as follows. For example, the time to switch to the next unbalanced connection starting at a phase difference of 60 ° is set to 4 to 5 seconds after the start, and the time to switch from unbalanced connection to 0 ° is set to 4 to 5 seconds after switching to the unbalanced connection. Thus, the phase switching device 20 sequentially switches three stages from 60 ° to 0 °. Needless to say, the above-mentioned time limit should be changed to an optimum value depending on the load.

In the case of the control device 23, the control device may include a simple logic circuit or, if necessary, a microprocessor. Further, upon receiving the signal of the detector 24,
A circuit for converting the signal as necessary, a circuit for comparing the converted signal with a predetermined reference value, a circuit for storing the predetermined reference value, and a signal output for outputting a signal by the previous comparison It will have a circuit and the like. With the signal of this signal output circuit, the phase switching device 20 is sequentially switched to change the phase difference. Also, the detector is a speed detector 24 here.
However, means for detecting the state of the electric motor such as one for detecting the number of rotations is used.

By controlling the phase switching device by the control device, the torque characteristic becomes as shown in FIG. 9, and the variation in torque is small and the starting current can be suppressed to be small as compared with the conventional star-delta switching.

By the way, the time limit of the control device 21 and the predetermined reference value of the control device 23 correspond to the load torque and the GD ^2.
And the output of the motor. Further, each control device is a simple device that only controls opening and closing of two short-circuit switches, and is configured as a control device of an induction motor having a three-stage phase difference incorporated in the phase switching device of the short-circuit switch. It is also possible.

In the above-described embodiment, the short-circuit switch is formed by a simple open / close contact. However, as shown in FIG. 10, the short-circuit switch is also used for a trigger element or the like. The device includes a device capable of switching, that is, a semiconductor device such as a thyristor or a triac. When such a short-circuit switch is used and, for example, gradually shifts from a series delta connection to an unbalanced state, a small torque fluctuation at the time of switching as shown in FIG. 9 is eliminated and a torque characteristic without a step shown in FIG. 11 is obtained. Can be done.

Although the three-stage torque characteristic has been mainly used in the embodiment, it is needless to say that a method of simultaneously closing the short-circuit switches and simultaneously short-circuiting all the lines can be realized depending on the load condition. Unlike ordinary star-delta switching, there is no interruption of the load current by switching, and since the plurality of stators are used, the phases can be switched at the same time, and the torque characteristic can be switched from the starting torque characteristic to the operating torque characteristic. The simple and inexpensive configuration of the switching device has the same effect as the above embodiment.

[0036]

As described above, the torque of the plurality of stator induction motors can be set in three stages by a simple phase switching device, and the three types of torques are for starting, medium speed, and driving. These torque characteristics are suitable motors for the purpose of improving the startability of the constant torque characteristic or the squared reduction torque characteristic, and reducing the start-up time, except for equipment that always requires a variable speed. There is no need for expensive control equipment. In addition, since wiring to the motor is configured by integrating the phase switching device, which is simply configured, with the motor, it is possible to wire the motor with anyone, as long as three wires are sufficient and the rotation direction is not misunderstood. is there.

Therefore, it is possible to diversify the torque and to expand the applications of the multiple stator induction motor capable of generating a high torque from a low speed to a rated rotation range, and to further contribute to any field requiring a high torque motor. Now you can.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a two-stator induction motor.

FIG. 2 is a connection diagram of a phase switching device.

FIG. 3 is a connection diagram at a phase difference of 60 °.

FIG. 4 is a connection diagram in an unbalanced state.

FIG. 5 is a connection diagram of a parallel star connection with a phase difference of 0 °.

FIG. 6 is a torque characteristic curve diagram in each connection.

FIG. 7 is a control block diagram based on a timer sequence.

FIG. 8 is a control block diagram of a logic circuit.

FIG. 9 is a torque characteristic curve diagram when the phase difference switching device of the present invention is used.

FIG. 10 is a wiring diagram using a thyristor for a short-circuit switch.

FIG. 11 is a torque characteristic curve diagram when a thyristor or the like is used.

FIG. 12 is a torque characteristic curve diagram by conventional star-delta switching.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Two stator induction motor 2, 3 Rotor core 4 Rotor shaft 5 Non-magnetic material core 6 Rotor conductor 7 Rotor 8 Short circuit ring 9 Resistance material 10, 11 Stator winding 12 First stator 13 Second stator Slave 14 machine frame 20 phase switching device 21 controller 22 power supply side 23 controller 24 speed detector S ₁ first short-circuit switch S ₂ second short-circuit switch

Claims (7)

(57) [Claims] A first rotor core and a second rotor core axially mounted on the same rotation axis with a space or a non-magnetic material portion interposed therebetween;
A cage-shaped integral rotor formed by mounting a plurality of conductors communicating with the second rotor core on an outer peripheral portion of the rotor core, and forming a first cage facing each of the rotor cores; A stator core and a second stator core are provided around, and a first stator winding wound around the first stator core and a second stator winding wound around the second stator core are formed. A first delta connected in series so as to generate a predetermined phase difference between the phase of the rotating magnetic field of the first stator winding and the phase of the rotating magnetic field of the second stator winding.
A stator and a second stator, which are provided between a series connection midpoint of an arbitrary phase and another two-phase series connection midpoint of each stator winding of the first stator and the second stator; The first stator winding and the second stator winding are switched from a series delta connection to a parallel star connection by closing the switch while energizing each of the stator windings. A rotating magnetic field generated around the first rotor core opposed to the first stator;
A phase switching device that reduces a phase difference between a stator and a rotating magnetic field generated around a second rotor core facing the stator by a predetermined electrical angle from a predetermined phase difference at the time of startup; and a switch of the phase switching device. And a control device for controlling opening and closing of the two-stator three-phase cage induction motor. 2. The two-stator three-phase squirrel-cage induction motor according to claim 1, wherein the predetermined phase difference at the time of startup is one.
80 °, 120 °, or 60 °, and the phase difference after switching from the series delta connection to the parallel star connection by the switch is 120 °, 60 °, or 0 °, respectively. Stator three-phase squirrel-cage induction motor. 3. The two-stator, three-phase squirrel-cage induction motor according to claim 1, wherein a series connection midpoint of an arbitrary phase of each stator winding of the first stator and the second stator is connected to another two-phase stator winding. When only one of the two switches provided between the two series-connected midpoints of the phases is closed, the first stator causes a rotating magnetic field generated around the first rotor core facing the first stator. And an unbalanced connection that produces a specific phase difference between the second stator and a rotating magnetic field generated around a second rotor core facing the second stator. Induction motor. 4. A two-stator three-phase squirrel-cage induction motor according to claim 1, wherein the phase switching device and the control device are integrally mounted on a main body of the induction motor. Three-phase cage induction motor. 5. The two-stator three-phase squirrel-cage induction motor according to claim 1, wherein the control device has a timer circuit for controlling a closing time of the switch based on a preset time period from a start time. A two- stator three-phase cage induction motor characterized by the above-mentioned. 6. The two-stator three-phase squirrel-cage induction motor according to claim 1, wherein the control device controls a closing time of the switch based on a preset number of revolutions from the time of activation. A two-station three-phase squirrel-cage induction motor characterized by having a heater. 7. The two-stator, three-phase squirrel-cage induction motor according to claim 1, wherein a series connection midpoint of an arbitrary phase of each of the stator windings of the first and second stators is connected to the other. A two-stator three-phase squirrel-cage induction motor, wherein the switch provided between the two-phase series connection midpoint is constituted by a semiconductor element capable of opening and closing a circuit and capable of controlling a conduction amount.