JPH0255599A - Switchable winding type ac motor - Google Patents

Abstract

PURPOSE:To enable switching between high speed and low speed without requiring a mechanical gear by switching the connection of each phase coil through a switching means. CONSTITUTION:Contactors S11-S34 are provided for respective phase coils. When high speed operation is performed, contactors S11-S31, S14-S34 are closed while contactors S12-S32, S13-S33 are opened, thus connect the phase coils in delta. When low speed operation is performed, the contactors S11-S31. S12-S32 are closed while the contactors S13-S33, S14-S34 are opened, thus connecting the phase coils in double delta. When very low speed operation is performed, the contactors S11-S31, S14-S34 are opened while the connectors S12-S32, S13-S33 are closed, thus connecting the phase coils in star.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a winding switching type AC motor suitable for use in the main shaft drive of a mission-less, high-output machine tool, and an AC motor equipped with this AC motor. The present invention relates to an output switching method for a machine tool having a C-axis control function.

(Prior art) In order to control a normal AC motor over a wide rotational speed range, the output varies depending on the speed, so a gear mechanism is used to switch between low and high speeds, which provides stable output characteristics. had been realized. In addition, for example, in machine tools that have a C-axis control function that requires spindle angular position control, it is possible to rotate the spindle smoothly and at an extremely low speed during contouring (die-sinking) processing, while also producing high output. I needed it. In particular, during C-axis control, sufficient machining accuracy cannot be obtained unless the rigidity of the spindle is increased. Therefore, in the past, a low-speed motor and a high-speed motor were provided and used by switching between them, and orientation accuracy was ensured by switching the servo gain.

(Problem to be solved by the invention) This conventional output switching method for machine tools with a C-axis control function has many disadvantages in terms of cost and structural space. Since it relies only on low-speed characteristics, there is a problem in that sufficient precision in spindle orientation and machining cannot be obtained.

The present invention was made to solve the above problems, and
The object of the present invention is to provide a winding switching type AC motor that can switch between low speed and high speed without using a mechanical gear mechanism.

(Means for Solving the Problems) According to the present invention, in an AC motor having an intermediate terminal for dividing and using the winding of each phase coil in addition to a three-phase AC input terminal, each phase The first switching means includes a first switching means for switching the connection state of the coil, and a second switching means for selecting the number of windings to be used of the windings of each phase coil. It is possible to provide a winding switching type AC motor characterized in that the winding structure of the coil is changed by the second switching means and the motor output characteristics are switched according to the rotation speed.

(Function) When the winding switching type AC motor of the present invention is applied to a machine tool that has a C-axis control function on the main shaft, it is possible to increase the rigidity of the main shaft in an extremely low speed region, and it is stable over a wide range. It is possible to achieve the desired output characteristics.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the state of electrical connection between each phase coil in a three-phase AC motor consisting of U, V, and W, and contacts Sll to S34 for changing the winding structure of these coils. Input terminals R, S, and T for power supply are single-blade terminals U1. Connected to V1 and Wl, and the other terminals X, Y, and Z are contacts S14. S24. S
It is connected to the neutral point N via 34. Also, above-
Thousand terminals U1. V1 and W□ are respectively contacts S12
．． S22. These contacts S14. are connected to the other terminals Z, X, and Y of the adjacent coils via S32.
S24. S 34 or contact S 12. S
22. By closing either one of S32, the coil connection state is switched from Δ (delta) connection to human (star) connection.

Each of the above-mentioned phase coils has an intermediate terminal u2. For example, the winding groups xi and x2 of the U-phase coil are connected to the terminal Ul via the contact Sll, and the winding groups xl and x2 and the contact Si
A contact S13 is connected in parallel to t. Winding group X1'+ of the coil divided by the intermediate terminal U2
x2' is a winding group X□ in the slot of the AC motor as described later.

x2, and in order to simplify the explanation, an example is shown in which only one intermediate terminal U2 is provided to divide the coil into two.

Then, by closing either one of the contacts Sll and S13, a selection is made to increase or decrease the number of windings used in the U-phase coil, and a similar selection is made simultaneously for the (2) and W-phases.

FIG. 2 is a diagram showing the coil arrangement of an AC motor having a 36-slot stator and the winding structure of the U-phase coil.

The slots in FIG. 2(a) are numbered clockwise from 1 to 36, and among the windings shown in FIG. 1
The coils are inserted in the order of 1.3.10 to form the first winding group x1, and the following coils are inserted into the slots 19, 30, 20, 2
The windings 9, 21 and 28 are inserted in this order to constitute the second winding group x2. The coil that has passed through the slot 28 is inserted into the slot 1 again via the intermediate terminal U2. Thereafter, the winding groups Xt' and x2 of the coils are inserted through the slots in the same order, and the coil that has passed through the last slot 28 is terminated at the other terminal X.

Note that the stator can be constructed in the same way even if the AC motor has a larger number of slots, and when power is supplied by voltage control, the value of the current flowing through the windings inserted through each slot and the number of windings can be changed in the same way. Although the output changes depending on the rotation speed, the resistance characteristics of the two coils can be easily changed by using windings made of different materials for the coils on both sides of the intermediate terminal.

Next, referring to FIGS. 3 to 5, the contactor Sl
The motor output characteristics obtained when the contact states of I to S34 are switched will be explained.

In Fig. 3(a), in order to obtain high-speed characteristics, each phase coil is divided and used, power is supplied from the input terminal to only the winding groups x, ', x2, and the coil connection state is Δ( Delta) connection. Note that in the contacts in each figure, 10 indicates an OFF state, and 2 indicates an ON state. In this case, as shown in FIG. 6(b), the output characteristic becomes a constant output from the time when the base rotation speed, which is set to a high rotation speed, is exceeded.

FIG. 4(a) shows a state in which the winding structure has been changed to realize low speed characteristics by using all the windings of each phase coil. In this case, for example, considering the strength of the magnetic field generated by the U-phase coil, a magnetic field is formed that is proportional to the number of windings inserted into each slot of the AC motor and the rotation speed, so the AC motor is used in a low speed region. In this case, when the rotational speed decreases, a larger output can be expected by increasing the number of effective windings, and conversely, in order to obtain the same level of output in a high-speed region, the number of windings may be smaller. In other words, as shown in FIG. 4(b), the base rotational speed shifts from the characteristics in the case of FIG. 3, and a constant output is obtained in the low speed region, so the winding division ratio by the intermediate terminal U2 can be adjusted appropriately. By setting it to , constant output characteristics can be achieved over a wide range.

FIG. 5 shows a state in which the winding structure has been changed to realize extremely low speed characteristics by further switching the connection state of each phase coil from Δ connection to S connection.

In other words, by switching this connection state, the base rotation speed is further reduced by 1/f1, so for example, in order to perform C-axis control, the base rotation speed can be reduced to 1100 rpm or less, and the main shaft can be directly connected to the output shaft of the AC motor. , it becomes possible to increase the rigidity of the main shaft. As shown in FIG. 6(b), the torque in this speed range can be increased, but the same output level cannot be obtained because the impedance increases.

The above-mentioned changes in the coil winding structure of an AC motor include three changes from each phase (for example, U, U2, U2, X for a U-phase coil).
), a total of nine lead wires need to be drawn out, and four contacts are used in common for each phase to switch simultaneously. Then, high-speed characteristics (Figure 3) and low-speed characteristics (Figure 4)
The contact states for realizing the extremely low speed characteristics (Fig. 5) are summarized in the table below.

Note that the contacts constituting each group of contacts are, for example, contactors such as magnetic contacts (MCC). If the machine tool is instructed to perform machining in an extremely low speed range, such as a C-axis control command, by automatically switching the contacts to the state shown in Figure 5 above, the main shaft can be directly connected to the AC motor. High torque can be achieved, and the spindle can be controlled with high precision even in response to orientation commands for stopping the spindle in a fixed position.

As above, this invention has been described in some detail with respect to its most preferred embodiment, but the description of the preferred embodiment does not include variations in detailed parts of the configuration or contrary to the spirit of the invention as described in the claims. It is clear that various modifications or combinations thereof may be made.

(Effects of the Invention) As explained above, according to the present invention, it becomes possible to switch the spindle output of a machine tool without a transmission, and the spindle rotation becomes high torque especially during C-axis control. Since the main shaft is rotated with high torque during operation and the rigidity of the main shaft can be increased, it is possible to provide a winding switching type AC motor in which processing accuracy can be easily improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the winding switching type AC motor of the present invention, Fig. 2 is a diagram showing the coil arrangement and winding structure, and Figs. 3 to 5 show the contact states. FIG. 3 is a diagram showing the motor output characteristics corresponding to the motor output characteristics. Sll-S34... Contact, R, S, T... Input terminal for power supply, N... Neutral point. Patent applicant Fanuc Co., Ltd. Agent Patent attorney Minoru Tsuji Patent Applicant Name Representative 4, Agent FANUC CORPORATION Ina Pa Seiu E Mon Inaha Seiemon November 2, 1988 (Shipment 63.11.29) 6.
Amendment band for drawing procedures to be amended (voluntary) December 23, 1988 Patent application No. 205894 Name of the invention Relationship to the person who makes amendments to winding switching type AC motor Patent applicant name FANUC CORPORATION Inaba Seiuemon Representative Inaba Seiemon 4, Agent 6゜7゜Object of amendment Contents of amendment Drawing Figure 2 (a) will be corrected as shown in the attached sheet.

Claims (2)

[Claims] (1) In an AC motor that has an intermediate terminal for dividing and using the windings of each phase coil in addition to the three-phase AC input terminal,
a first switching means for switching the connection state of each phase coil with respect to the input terminal; and a second switching means for selecting the number of windings to be used of the windings of each phase coil; Second
A winding switching type AC motor, characterized in that the winding structure of the coil is changed by the switching means, and the motor output characteristics are switched according to the rotation speed. (2) In the machine tool in which the main shaft is directly connected and driven to the output shaft of the winding switching type AC motor according to claim (1),
The first and second switching means are switched based on an extremely low speed control command issued to the AC motor, and each of the three-phase coils is star-connected using all windings to switch the spindle output of the machine tool. output switching method.