JPS59191461A - Squirrel-cage induction motor - Google Patents

Abstract

PURPOSE:To enable to control a starting current of a squirrel-cage induction motor by splitting a stator of the motor, varying the relative position between the split stators, then displacing the phase of an electromotive force induced in the squirrel cage winding, thereby suppressing the current flowed to the winding. CONSTITUTION:The first and second stators A, B respectively have stator windings 8A, 8B, the stator A is secured to a frame 9 of a motor, and the stator B is secured to circumferentially rotate to the frame 9. 3-phase alternating currents are flowed to the windings 8A, 8B so that the directions of the rotary magnetic fields becomes the same. A starting current is continuously widely controlled by varying the relative position between the stators A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a squirrel cage induction motor, and particularly to an improvement in its starting current suppressing means.

FIG. 1 shows the configuration of a squirrel cage induction motor that has been commonly used in the past.

In this figure, (1) is the bracket, (2) is the bearing, (
3) is the rotating shaft, (4) is the rotor core, (5) is the rotor conductor, (6) is the end ring that shorts both ends of the rotor conductor to form a squirrel cage winding, and (7) is the fixed The child core (9) is a stator winding.

In the squirrel cage induction motor configured in this way, as is well known, a rotating magnetic field is generated by supplying three-phase alternating current to the stator winding (8), and this and the rotating magnetic field flowing to the rotor cage winding are generated. Torque is generated by the child current and the rotor core (7) rotates.

It should be noted that star-delta starting, reactor starting, starting compensator starting, etc. are known as means for suppressing the starting current of such squirrel cage induction motors, but all of these methods can only suppress the starting current in stages. The suppression value also has drawbacks such as the fact that the value cannot be changed once the starter is installed.

In addition, there is a secondary resistance control method using a wound induction motor as a means of continuously controlling the starting current, but since a wound trochanter is required, the motor itself becomes structurally complex and expensive, and the secondary resistance It requires an accessory device such as a metal resistor or a liquid resistor as a resistor, or a control device to change the resistance value of these resistors. Moreover, the secondary resistance control scheme has the drawback of generating large amounts of power dissipation within the resistor.

Another suppression method is to improve the characteristics of the motor itself and limit the starting current to a low level without using a special starting device, but suppressing the starting current to a low level will affect the torque characteristics. At most, the rated current is 350 ~
The limit is to suppress the starting current to about 400%.

However, in this case, there is a drawback that the capacity of the power supply transformer is required to be several times the amount of power used in order to suppress the voltage drop in the transformer which is caused by the starting current.

This invention was made in order to eliminate such conventional drawbacks, and by dividing the stator of a squirrel cage conductive motor into two and changing the relative position between the stators, it is possible to induce the squirrel cage profile line. The present invention aims to provide a squirrel-cage conductive motor in which the phase of the electromotive force is shifted to suppress the current flowing through the squirrel-cage profile line, thereby making it possible to continuously control the starting current over a wide range.

An embodiment of the present invention shown in FIGS. 2 to 8 will be described below. In Fig. 2, (9) is the frame of the motor; (B) is the first stator having a stator winding (8A) fixed to the frame and to which three-phase voltage is applied; This is a second stator that has the same configuration as the stator and has a stator winding (8B), but is attached to the frame (9) so that it can rotate in the circumferential direction.NO Chi,
A ring-shaped washer (10) is attached to the outer periphery of the second stator, and a support (11) for supporting the washer (10) is provided on the frame (9) over the entire circumference of the frame. , the support (11) and the washer (10) are configured to be able to slide against each other.

(12) is a transmission rod fixed to the second stator and protrudes from the outer periphery of the frame (9); (13) is a piston (14) coupled to the transmission rod; and a sillage device for driving this piston. tf (15), pressure oil supply ports (16) provided at both ends of the cylinder device,
By supplying pressure oil from either one of (17), the second stator (B) can be rotated in the circumferential direction of the frame. The second stator is configured to be able to rotate within a range corresponding to one pole pitch of magnetic poles generated by applying three-phase alternating current from the outside.

(18) is a rotor core having a length that can accommodate the first stator (N) and the second stator (E), and constitutes a rotor common to both stators. The rotor conductor attached to the child core, (6) is an end ring that shorts both ends of the rotor conductor to form a squirrel cage wire.Other configurations are the same as the conventional one, so no explanation will be given. Omitted.

When three-phase alternating current is applied to the first and second stators of the squirrel-cage conductive motor configured in this way so that the directions of the rotating magnetic fields are the same, the squirrel-cage profile line of the rotor has a third stator. As shown in the figure, the current flow by the first stator (A)
The electric current 8 by the second stator (B) flows.

Therefore, if the two stators (A) and (B) are positioned so that there is no phase difference between the poles of their respective currents, the result will be as shown in FIG. Since currents 8 and 8 are the same in both direction and magnitude, the rotor's cage profile line is a current that combines both currents. flows.

Further, the second stator (B) is replaced by the first stator (N is a convection pipe, and the convection pipe is as shown in FIG. 5, and the waveform of the combined current pipe is reduced and deformed.

Furthermore, when the second stator (B) is displaced in the circumferential direction by an amount equivalent to one pole pitch with respect to the first stator (A),
is as shown in Figure 6, which is the composite electric current of both. cancel each other out and become almost 0. These phenomena can be expressed as an equivalent circuit as shown in FIG.

In this figure, the secondary peephole 2 has a secondary induced electromotive force Wt
+ (induced electromotive force by the first stator) and 22 (second
The combined electromotive force (induced electromotive force by the stator), secondary reactance X2 and secondary resistance r2/9 (9 is slip)
Determined by

In this circuit, the current T1.140 flowing into the conductive motor is calculated as follows: 1-111+12, and IIIε and T12 are each greatly influenced by the value of the secondary current Te2. Therefore, the current at starting is
The starting current of the squirrel cage induction motor can be controlled by changing the phase of the secondary induced ENN motor 2 and the ridge 2. In addition, in the above embodiment, the first stator and the second stator were made to have almost the same capacity, but it goes without saying that the controllable value can be changed by making the capacities of the two different. .

Also, by adjusting the position of the second stator, the eighth
As shown in the figure, since the torque generated by lightning and motive can also be changed from T1 to T2, it is easy to change the speed from nl to n2 with respect to the load torque. Therefore, this embodiment can also be used as a speed control device.

This invention is constructed as described above, and because one of the two stators arranged in parallel in the axial direction is displaced in the circumferential direction within a range corresponding to the pitch between poles, there is no need to use a special starting device. , the starting current of a squirrel cage conductive motor can be continuously controlled. It also has the effect of making speed control possible during driving.

[Brief explanation of drawings]

Fig. 1 is a partial cross-sectional view showing the configuration of a conventional squirrel cage conductive motor, Fig. 2 is a partial cross-sectional view showing an embodiment of the present invention, and Fig. 3 is a partial cross-sectional view showing the structure of a conventional squirrel cage conductive motor. Fig. 4 is an explanatory diagram showing the 'FI flow transmitted through the two stators of the above embodiment,
An explanatory diagram showing the current induced in the squirrel cage winding when the poles are positioned so that there is no phase difference, and an explanation showing the induced 1°C current in the squirrel cage winding when the squirrel cage winding is displaced in the second position. Figure 6 shows that the second stator is IFf equivalent to the pole pitch.
Explanatory diagram showing the induced current when displaced in the l direction, 7th
The figure shows an equivalent circuit of the above embodiment, and No. 81 also shows a torque characteristic diagram. In the figure, (A) is the first stator, (B) is the second stator,
(10) is a washer, (11) is a support metal, (12) is a transmission rod, (14) is a piston, (15) a cylinder device, (18)
) is the rotor core, (5) is the rotor conductor, (6) is the end ring, and (3) is the rotating shaft. Note that the same reference numerals indicate the same or corresponding parts. Agent: Masuo Oiwa, Patent Attorney Figure 1 Figure 6 Hiro Figure 7 Figure 8

Claims (1)

[Claims] 1. A first stator and a second stator having the same number of poles and the same number of slots as the first stator are arranged in parallel in the axial direction, and A squirrel cage rotor having a length that can accommodate the first and second stators and common to both stators is provided, and the second stator is displaced in the circumferential direction within a range equivalent to one pole pitch. A squirrel cage induction motor characterized by: 2. The squirrel cage induction motor according to claim 1, wherein the second stator is displaceable in the circumferential direction by a hydraulic device. 3. The squirrel cage induction motor according to claim 1 or 2, wherein the first stator and the second stator have the same capacity. 4. The squirrel cage induction motor according to claim 1 or 2, wherein the first stator and the second stator have different capacities.