JPH01206891A - Motor - Google Patents

Abstract

PURPOSE:To miniaturize an apparatus and to lower its cost by constituting respective phase windings from part winding groups, by dividing said windings into groups according to a rotational speed and by providing said apparatus with connection change-over means for series connection within a group and for parallel connection between groups. CONSTITUTION:A servo control circuit for three-phase AC synchronous motor is composed of an encoder 11 detecting the rotational position of a motor 10, a deviation counter 12, a D/A converter 13, an amplifier 14, a three-phase synchronous rectifier 15, an inverter part 17, a converter part 18 and others. Further, an output current is fed back from the inverter part 17 to a current amplifier 16 and a speed signal, from an F/V converter 21. Also, a motor winding is composed of U-W-phase windings 1-3, which are divided by a multiplier of 2 respectively and connected with a winding change-over part 20 to form respective phase part windings 1a-3b into series and parallel connection state. Thus, connection change-over of said windings 1-3 is performed by a signal from a change-over command part 22 according to the number of revolutions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to motors, and particularly to motors. The present invention relates to a motor that can be suitably used as a motor for directly driving a meditation.

Since the main spindle in conventional technical machine tools is used with a constant output load over a high-speed rotation range to a low-speed rotation range, the motor and the main shaft are usually not directly connected, but are connected via a transmission mechanism. This allows a relatively low-output motor to provide a constant output over a wide range of rotational speeds. In other words, in the stator of a motor commonly used to drive the main shaft of a machine tool,
The U-phase, ■-phase, and W-phase windings are arranged at 120° intervals, and each phase winding is made by connecting multiple coils in series.
It has been t&.

Challenges for Inventions to Be Decided on C By the way, in modern machine tools, there is a strong need to automate high-precision machining! 71, and for this reason it has become necessary to directly drive the spindle. However, to directly drive the motor as described above requires a motor with a very large rated output in order to obtain the specified output in the low speed and high speed ranges, which poses the problem of increased loss. .

For example, in order to obtain a specified output value in the range of 800-8700 r, p, m, in order to obtain the specified output value at both ends of the rotation speed range, it is necessary to It is necessary to use a motor with a rated output that is extremely large compared to the output that is used, and there is a problem in that the motor becomes abnormally large and loss increases accordingly.

Therefore, the present applicant first constructed a motor in which the number of windings was changed according to the rotational speed, specifically, the winding was divided into a plurality of divided winding groups, and the divided windings were For example, as shown in Fig. 4(n) and (b), a connection switching means is provided to connect each group in series and connect the groups in parallel. In the range, the number of windings is increased to obtain the output characteristic P, which has the maximum output in the low speed range, and in the medium and high speed range, the number of windings is decreased to obtain the output characteristic P2, which has the maximum output in the medium and high speed range, respectively. By obtaining P3, we have proposed a motor that can obtain a predetermined output over a wide rotational speed range while using a small motor with a low rated output.

However, when the connection of the divided windings is switched, no current flows through the windings, and the output becomes zero instantaneously. Therefore, it is limited in that it cannot be applied to machining that requires switching the connection of windings in order to vary the rotational speed over a wide range during machining. However,
In the automation of machine tools, it is necessary to keep the circumferential speed of the machining point constant in order to maintain constant machining conditions. Therefore, it is necessary to vary the rotation speed over a wide range according to changes in the diameter of the machining point, and the above limitations cannot be met. This is an extremely important issue to resolve.

In view of the above problems, it is an object of the present invention to provide a motor that can directly drive the main axis of a machine tool, is small and inexpensive, and can be used over a wide rotational speed range.

Means for Solving the Problems In order to achieve the above object, in the motor according to the present invention, the windings of each phase are configured into eight divided wire groups, and the divided windings of each phase are divided according to the rotational speed. The method is divided into one or more groups, and is provided with a connection switching means for connecting one group in series and connecting the groups in parallel, and this connection switching means is configured to sequentially switch the windings of each phase, and further A switching command means is provided for commanding the connection switching means to switch the connection of the eight wires of each phase when the current value of that phase is zero or near zero. Preferably, the terminal ends of the windings of each phase are not coupled to each other or to the starting ends of the windings of other phases, and the current control of the windings of each phase is performed independently.

According to the present invention, by sequentially switching the connection of the divided windings for each winding of each phase, the remaining two phases are driven even at the time of switching, and it is possible to obtain an output of at least 50% of the rated output. This makes it possible to use it in a rotational speed range that requires connection switching.

Furthermore, by performing the above switching when the current flowing through that phase is zero or near zero, it can be used with almost no influence from the connection switching.

Furthermore, by controlling the current of the windings of each phase independently, the current value can be completely reduced to zero at the time of switching, thereby preventing destruction of the switching element and saving its life.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG. 1 to FIG. fjS4.

The motor windings are U-phase winding 1, ■ phase 8 wire 2, and W-phase winding 3.
2, 4, 8, etc., respectively (the examples in FIGS. 1 and 3 are divided into two), and each divided winding 1a, 1b, 2a , 2+) , 3a
, 3b, as shown in FIG.
0, and as shown in FIGS. 1(a) to (d), the divided windings 18 to 3b of each phase are configured to be switchable between a state where they are connected in series and a state where they are connected in parallel.

Although not shown, when the windings of each phase are divided into four parts, all the divided windings are connected in series, and two V18 wires each are connected in series. It is configured such that it can be switched between a state in which all the divided windings are connected in parallel and a state in which all divided windings are connected in parallel.

Next, the usage mode and output characteristics when the winding is divided into four and the connections are switched will be explained with reference to FIG.

If the motor is used at low rotation speeds of 800-2000 r, p, +n, all split windings are connected in series.

Then, the total number of turns of the winding becomes the number of turns, the rotation speed-torque characteristic at that time becomes T in Fig. 4 (a), the rotation speed - output characteristic becomes Pl in Fig. 4 (b), and the above-mentioned low speed A predetermined (8 KW in the illustrated example) constant output can be obtained by controlling the current according to the rotation speed in the rotation range. Incidentally, startup control is performed by constant torque/constant current control until the motor reaches a predetermined output and rotation speed.

Further, when the motor is used at medium speed rotation of 1500-4500r, p, +a, two divided windings each connected in series are connected in parallel. Then, the number of windings becomes one half of the total number of turns of winding 1, and the rotation speed-torque characteristic at that time is 72 as shown in Figure 4 (,), and the rotation speed-output characteristic is I:JS4 diagram (b) P2, and a predetermined constant output can be obtained by controlling the current according to the rotation speed in the medium speed rotation range. At startup, all the divided windings are connected in series to control the low speed rotation, and as the rotational speed increases, the connection of the eight divided wires is switched.

Further, when the motor is used at high speed rotation of 3500-8700r, p, +n, all the divided 8 wires are connected in parallel to each other. Then, the number of windings becomes one quarter of the total number of turns of winding 1, and the rotation speed-torque characteristic at that time is shown in Figure 4 (
T1 in a), the rotational speed-output characteristic becomes P3 in FIG. 4(b), and a predetermined constant output can be obtained by controlling the current according to the rotational speed in the high speed rotation range.

Incidentally, when the motor is used at low speed, medium speed, and high speed rotation, the connection of the divided windings is naturally switched according to the rotational speed during operation.

Next, this connection switching will be explained based on FIGS. 1 to 53. In addition, to simplify the explanation, 84 of each phase
An example in which Q is divided into two will be explained.

When switching from a low-speed rotation state in which split windings are connected in series to parallel connection due to an increase in rotational speed, all of the 8#X split windings in the U, ■, and W phases are From the series connected state, first, as shown in Fig. 1(b),
Switch only the phase divided windings 1a and 1b to parallel connection, and then connect the phase divided windings 2a and 2b as shown in Fig. 1(c).
are switched to parallel connection, and finally, as shown in FIG. 1(d), the W-phase divided windings 3a, 3I) are switched to parallel connection.

In this way, by switching the connections of the windings of each phase sequentially, current flows through the windings of other phases at the time of switching, so it is possible to suppress the drop in output to 50% or less. .

Conversely, when switching from parallel connection to series connection, it is sufficient to switch sequentially in the opposite manner to the above.

Furthermore, the switching of the windings of each phase is as shown in Figure 2.
When the current flowing through that phase is zero or near zero, that is, the U-phase winding 1 is switched at timing T1, the ■-phase winding m2 is switched at timing T2, and the W-phase winding 3 is switched at timing T2. I try to do each with T. In this way, by switching the windings of each phase when the current flowing through that phase is zero or close to zero, the switching hardly affects the output.

Furthermore, as shown in Fig. 1 and rjS3, the terminal ends of the windings of each phase are not connected to each other, and the current control of the windings of each phase is performed independently, so that the current control of the windings of each phase is performed independently. Since no current flows from other windings and the current value is maintained at completely zero, it is possible to prevent destruction of the switching element and save its life.

Next, a servo control circuit for a three-phase AC interphase motor having a configuration for switching the windings as described above will be described with reference to FIG.

An encoder 11 for detecting the rotational position of the motor 10 having each of a1 to a3 is coupled to the motor 10, and its output signal and position command human power pulse are input to a deviation counter 12. The output from this deviation counter 12 is sent to the D/A converter 13.
The signal is converted into an analog signal by the amplifier 14, and is then amplified by the amplifier 14 and input to the three-phase synchronous rectifier 15. From the three-phase synchronous rectifier 15, an output signal corresponding to the deviation from the amplifier 14 and the rotational position of the motor obtained from the signal from the encoder 11 should be sent to each phase! A current value is calculated and a corresponding current is output, amplified by a current amplifier 16, and input to an inverter section 17. A power source is input to the inverter section 17 as a power source via the converter section 18, and a current controlled according to the current from the current amplifier 16 is passed through the winding switching g20 to each of the eight wires 1.2. 3 has already been entered.

Note that the output current from the inverter section 17 is detected and fed back to the current amplifier 16. Further, the amplifier 14 is fed with a speed signal from an F/■ converter 21 that converts the frequency of the output pulse of the encoder 11 into a speed signal.

The winding switching unit 20 is configured to switch the connection of the windings based on a signal from a switching command unit 22. A speed signal from the F/V converter 21 is inputted in order to switch the connection, and a position signal from the encoder 11 is inputted in order to switch the connection at the position where the current of each phase is zero. Also, when switching the connection of a winding, the flow should be applied to that winding! ! - Since the current value changes, this switching command section 22
A current rimming command is output from the current amplifier 16 to the current amplifier 16.

With the above circuit configuration, the winding connection switching as described above can be performed automatically.

In the above embodiment, an encoder is used to detect the rotational position of the motor, but a resolver may also be used, and the position can also be directly detected by a magnetic saturation element using the magnetic poles of the rotor. You may also do so.

In addition, in the example shown in Figure 1, 8ai and 2.3 correspond to star connection, and the corresponding current flows through each winding independently, but if the capacity of the switching element is large, star connection is used. Furthermore, in the present invention, the windings may be connected in a delta manner, or the starting and ending ends of these windings may not be connected, and corresponding currents may be made to flow through each winding independently.

Effects of the Invention According to the motor of the present invention, the number of windings can be changed according to the rotation speed as described above, so the number of windings is increased in the low speed rotation range to increase the output in the low speed range. In the high-speed rotation range, the number of windings can be reduced to obtain the maximum output in the high-speed rotation range, and the specified output can be obtained over a wide rotation speed range while using a small motor with a low rated output. (The connection switching of the divided windings is performed sequentially for each winding of each phase), so the remaining two phases are driven even when the connection is switched.
It can be used in a wide rotational speed range where connection switching can be done at will, and by performing the above connection switching when the current flowing through that phase is zero or near zero, connection switching can be easily performed.
Furthermore, if the current of each phase winding is controlled independently, the current value can be completely reduced to zero at the time of switching, which prevents damage to the switching element and reduces voltage.
This has the great effect of being able to provide a small motor that can be automated by direct drive in machine tools, such as having a longer lifespan.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, and FIG.
) to (d) are explanatory diagrams showing the winding connection switching process, Fig. 2 is an explanatory diagram showing the switching timing, Fig. 3 is a control block diagram, and Fig. 4 shows the characteristics of the motor targeted by the present invention , (a
) is a rotation speed-torque characteristic diagram, and (b) is a rotation speed-output characteristic diagram. 1.2.3...8 wires la, 1b......divided windings 2a, 2b...
......Division - 8 lines 3a, 3b...
・Split winding 10・・・・・・・・・・・・・・・・・・
・・・Motor 11・・・・・・・・・・・・・・・・・・
・・・・Encog 20・・・・・・・・・・・・・・・・
...... Winding switching section 22 ......
・・・・・・・・・Switching command unit. Representative Patent Attorney Toshio Nakao and 1 other person - A 2 Figure

Claims (4)

[Claims] (1) The windings of each phase are composed of divided winding groups, and the divided windings of each phase are divided into one or more groups according to the rotation speed, and the groups are connected in series and the groups are connected in parallel. 1. A motor comprising a connection switching means configured to sequentially switch windings of each phase. (2) The motor according to claim 1, further comprising switching command means for instructing the connection switching means to switch the connection of the windings of each phase when the current value of that phase is zero or near zero. (3) The motor according to claim 2, wherein the switching command means receives a signal from the motor rotational position detection means and a signal from the motor rotational speed detection means. (4) The terminal ends of the windings of each phase are not connected to each other or to the starting ends of the windings of other phases, and the current control of the windings of each phase is performed independently. The motor described in 3.