JPS62107696A - Controller for 3-phase induction motor - Google Patents

Abstract

PURPOSE:To obtain a low speed inching operation in a DC current supply controlling state by supplying a DC current to the first winding of a pole change 3-phase induction motor having double windings to obtain a braking torque and combining the braking torque and a motor torque. CONSTITUTION:An induction motor 1 is formed in a double winding pole change induction motor, a DC current is supplied between the terminals U1 and V1 of a first winding, and a 3-phase AC current is supplied among terminals U2, V2, W2 of the remaining second windings. A controller 8 controls to close a switch 7 after controlling to close a switch 3 by closing the inching side of an operation switching command switch 9. Thus, the motor generates the composite torque of the braking torque and the motor torque to operate inching at low speed.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a control device for a three-phase induction motor, and particularly to a control device having a low-speed drive control function.

B8 Summary of the Invention The present invention provides a method for supplying direct current to the first winding set and supplying alternating current to the second winding of a double winding pole number conversion induction motor in low-speed inching operation of the induction motor. This allows reliable low-speed operation without complicating the control device.

C0 Prior Art In a device driven by an induction motor, if accurate positioning is required before starting, it is necessary to rotate the motor at a low speed and control it to a predetermined rotation amount. However, since it is difficult to provide a low-speed rotation function with a normal induction motor, the following method is actually used.

(1) Drive method.

(2) Method of utilizing the low speed side of the pole number conversion motor.

(3) Method using an inverter.

(4) A method that combines the above (1) to (3).

D1 Problems to be Solved by the Invention Regarding obtaining the position setting (by the conventional method), in the drive method described in item (1), with a normal electric motor (about 2 to 6 poles), the drive stop timing is inappropriate and the drive is stopped more than necessary. Otherwise, there is a problem in that the amount of rotation is less than that, and it takes time to set one position.

Regarding this point, the drive control on the low speed side of the pole number changing motor or the low speed operation control of the inverter according to the above item (2) or (3) makes position setting relatively easy.

However, in order to reduce the number of revolutions on the low-speed side, pole-changing electric motors are required to have a large number of poles, but with a motor of several kilowatts, it is difficult to increase the number of poles due to the manufacturing process. Even if it could be manufactured, there was a problem in that it would be difficult to obtain sufficient output.

Further, in the method using an inverter, a standard electric motor can be used, but the cost increases due to the inverter itself.

Means and operation for solving the E0 problem The present invention has been made in view of the above problems, and is capable of supplying direct current to the first winding of a pole-changing three-phase induction motor having double windings. , comprising a control means for supplying three-phase alternating current to the second winding, and setting a minimum torque lower than the starting torque to the composite torque of the braking torque generated by the direct current and the motor torque generated by the alternating current. A low operating speed is obtained at the intersection of this resultant torque and the load torque.

F. Embodiment FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention. The induction motor 1 is made into a double winding pole number conversion induction motor (the number of poles is arbitrary), and DC current is supplied between the terminals U, , and V of the first winding, and the second Winding terminal U, ,
A three-phase alternating current is supplied between V, , and W. Direct current that supplies direct current between terminals U, , and V1? [The power source is a single-phase AC power source 2 that supplies an AC input to a rectifier 4 via a switch 3, and the rectified output of the rectifier 4 is smoothed by a smoothing capacitor 5. terminal U,
, V, , W, an AC power source that supplies alternating current between them is obtained from a three-phase AC power source 6 via a switch 7.

Switches 3 and 7 are controlled to open and close by a control circuit 8. When the drive side of the operation changeover command switch 9 is turned on, the control circuit 8 closes the switch 3 and then closes the switch 7 to obtain a low-speed drive for the electric motor 1. In addition to this control, the forward/reverse command switch 10 is set to forward or reverse rotation. The phase order of switch 7 is changed accordingly. Also.

The control circuit 8 controls the switch 3 to open when the operation changeover command switch 9 is turned on to the steady state, and controls the forward/reverse command switch 10 to rotate forward or backward.
Closing control is performed by matching the phase sequence of the switch 7 in accordance with the reverse rotation setting.

In such a configuration, the visiting electric motor 1 is used for low-speed inching operation.
Direct current is supplied from the DC power source between the 0 winding terminals U, , V, and alternating current is supplied from the AC power source between the winding terminals U, , V, , W. At this time, the direct current of the induction motor 1 produces braking torque in the first winding, and the alternating current produces motor torque in the second winding. This braking torque and motor torque are Kυ as shown in Figure 2.
, a composite torque characteristic T obtained by superimposing the braking torque characteristic TN and the motor torque characteristic TP becomes the output torque characteristic of the electric motor 1. That is, since the braking torque due to DC braking reaches its maximum torque at low rotation speeds, there is a minimum torque value in the composite torque characteristic T where the starting torque also drops during the course of starting.

Therefore, load torque characteristic T1. is always the resultant torque characteristic T
If the magnitude is greater than the minimum torque of , the load torque characteristic TL
The intersection point P between and the composite torque characteristic T becomes the operating point of the electric motor 1. This operating point P can be changed significantly by adjusting the braking torque characteristic TH, that is, by adjusting the DC current, and by adjusting and setting the DC current according to the magnitude of the load torque characteristic TL, the speed of low-speed drive can be adjusted. It is possible to obtain low-speed drive without accelerating not only in no-load conditions but also in regenerative operation, and can rotate at low speeds even with fluctuating loads such as looms.

Note that in order to obtain low-speed operation that can be set even when the load fluctuates, the control circuit 8 is configured to have a DC power supply voltage control function. This is achieved by adjusting means.

In addition, the connection between the first winding of the motor 1 and the DC power source is the third
As shown in the figure, it can be changed as appropriate depending on the load and the like.

In addition, the control circuit 8 applies DC power and AC as sources, and applies AC current after applying DC current, thereby eliminating the inability to effectively utilize braking torque due to a delay in the start-up of DC. This is realized by a timer circuit or the like.

In addition, in the actual train, if the motor torque characteristic TP' of the motor 1 has a synchronous torque point S as shown in Fig. 4, a large negative torque can also be obtained by braking torque, and synchronous Uses torque to become even more effective.

G0 More than the effects of the invention 1 According to the present invention, a pole number changing three-phase induction with double winding! In order to obtain braking torque by supplying DC current to the first winding of the motor, and to obtain low-speed inching operation from the composite torque of this braking torque and the motor torque and the load torque, the control bag rItt--relatively simply. This has the effect of making arbitrary settings easy and ensuring low-speed inching operation.

Furthermore, since the DC braking torque is zero at the time of starting, the starting torque is determined by the electric motor torque, and a large starting torque is obtained to speed up the drive operation.

[Brief explanation of drawings]

Figure 1 is a device configuration diagram showing one embodiment of the present invention, Figure 2 is a torque characteristic diagram in Figure 1, and the third factor is the relationship between the first winding and the DC power supply, which shows another embodiment of the present invention. The connection circuit diagram and FIG. 4 are torque characteristic diagrams showing another embodiment of the present invention. 1...Double winding pole number conversion three-phase induction motor, 3.7...
・Switch, 4... Rectifier, 8... Control circuit, 9.
...Operation changeover command switch, 10...Forward/reverse command switch.

Claims (1)

[Claims] A control means capable of supplying a direct current to a first winding of a pole-changing three-phase induction motor having double windings and supplying a three-phase alternating current to a second winding, and controlling the supply of the direct current. A control device for a three-phase induction motor, which is characterized by performing low-speed inching operation in a controlled state.