JPH0424958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a secondary current detection device for an induction motor.

[Conventional technology]

In recent years, due to demands for energy saving and high efficiency, high performance control of induction motors has been performed by vector control.

Vector control methods that have been put into practical use are feed forward methods using microcomputer calculations, such as the ``primary voltage method'' and the ``current model method.''

In order to further improve this vector control system, it is necessary to detect the secondary current generated in the rotor, detect the electric torque resulting from the product of the detection signal and the main magnetic flux detection signal, and perform feedback control.

Therefore, the present inventors have conventionally developed a device for detecting the secondary current generated in the rotor in ``Study on detection of secondary current of induction machine using an amorphous micro core magnetometer'' (Journal of the Japanese Society of Applied Magnetics) VOL.8.
No. 2, 1984 reprint, pp. 229-232.

To explain this conventional device, as shown in FIG. 4, a rotor 4 of the induction motor rotates around a rotating shaft 5, and has end rings 6 on both end faces in the axial direction.

As shown in FIG. 3, magnetic cores 1b and 1c constituting the sensor section 1 are inserted into the end ring 6. Coils 1a, which are not shown in FIG.
1d is provided oppositely.

The magnetic cores 1b, 1c are composed of zero magnetostrictive amorphous magnetic alloy wire.

However, the magnetic cores 1b and 1c are not limited to zero magnetostrictive amorphous magnetic alloy wires, but may also be made of permalloy, ferrite, etc., and are not limited to wires as long as they are ferromagnetic.

Astable multivibrator 2 has coils 1a, 1
d, it self-oscillates and outputs in response to a magnetic field proportional to the secondary current of the end ring 6 of the rotor 4.

Next, the smoothing circuit 3 removes the AC component from the output from the astable multivibrator 2 and outputs only the DC component.

Further explaining the circuit configuration in detail, the power supply +E is connected to the coils 1a and 1d, respectively.

The coil 1a is further connected to the terminal T1 of the smoothing circuit 3 via the collector and emitter of the transistor Tr1.

On the other hand, the coil 1d is connected to the terminal T2 of the smoothing circuit 3 via the collector and emitter of the transistor Tr2.

Here, the transistors Tr1 and Tr2 perform a switching action.

A midpoint between the coil 1a and the collector of the transistor Tr1 is connected to the base of the transistor Tr2 via a parallel circuit of a capacitor C1 and a resistor R1.

On the other hand, the connection midpoint between the coil 1d and the collector of the transistor Tr2 is connected to the base of the transistor Tr1 via a parallel circuit of a capacitor C2 and a resistor R2.

Here, the capacitor C1 and the resistor R1, and the capacitor C2 and the resistor R2 perform a commutation function.

Next, the midpoint of the connection between the emitter of the transistor Tr1 and the terminal T1 of the smoothing circuit 3 is grounded via a resistor R3, and is also connected to a sliding terminal of a variable resistor VR for zero point adjustment.

Similarly, the midpoint between the emitter of the transistor Tr2 and the terminal T2 of the smoothing circuit 3 is grounded via a resistor R4, and is also connected to a sliding terminal of a variable resistor VR.

Further, the midpoint of the connection between the emitter of the transistor Tr1 and the terminal T1 of the smoothing circuit 3 is connected to the midpoint of the connection between the emitter of the transistor Tr2 and the terminal T2 of the smoothing circuit 3 via a variable resistor VR.

Output terminals T3 and T4 are connected to a control circuit (not shown) of the induction motor.

The above capacitors C1, C2, resistors R1, R
2, R3, R4, variable resistor VR, and transistors Tr1, Tr2 constitute an astable multivibrator 2.

Here, a secondary current signal S1 of the end ring 6 of the rotor 4 is detected by the sensor unit 1, and an output S2 of the smoothing circuit 3 is obtained via the astable multivibrator 2, which is input to the control circuit (not shown) of the induction motor. be done.

[Problem that the invention seeks to solve]

However, in the conventional device described above, there are many ripples in the detection signal S2 as shown in FIG. 5 due to vibrations in the rotational axis 5 direction of the rotor 4 or in the circumferential direction, and it cannot be used stably for control. There was a problem.

The present invention was proposed in order to solve the above-mentioned problems, and it is an object of the present invention to provide a secondary current detection device for an induction motor that stably detects the secondary current by reducing the ripples in the secondary current detection signal. purpose.

[Means for solving problems]

The present invention is intended to solve the above-mentioned problems, and includes a sensor section that is disposed opposite to the end ring of a rotor of an induction motor and is composed of a coil and a magnetic core made of a ferromagnetic material inserted into the coil.
an astable multivibrator connected to the coil that self-oscillates and outputs in response to the secondary current of the end ring; and a smoothing device that removes the alternating current component from the output from the astable multivibrator and outputs only the direct current component. This is an improvement on a secondary current detection device for an induction motor, which is comprised of a plurality of coils connected in series or parallel to each other, and a magnetic core inserted into each of the coils, A secondary current of an induction motor, wherein the coil and the magnetic core are arranged symmetrically about the rotation axis of the rotor, and are respectively arranged at mutually corresponding positions on both end rings of the rotor. It is a detection device.

[Effect]

Next, to explain the operation of the present invention, a plurality of coils and magnetic cores constituting the sensor section are arranged symmetrically around the rotation axis of the rotor, and are located at mutually corresponding positions on both end rings of the rotor. Because of the arrangement, even if the rotor of the induction motor vibrates in the axial direction or the circumferential direction, they complement each other, so a stable secondary current of the rotor of the induction motor with less ripple is detected.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the drawings.

FIGS. 1 and 2 are configuration diagrams of an embodiment of the present invention applied to an induction motor.

Most of the configuration is the same as the conventional device shown in FIGS. 3 and 4, but differs in the following points.

The sensor section 1 includes a plurality of coils 1a and 1d connected in series, and magnetic cores 1b and 1c inserted into the coils 1a and 1d, respectively.

Although the plurality of coils 1a and 1d are connected in series in this embodiment, they may be connected in parallel.

The coils 1a, 1d and the magnetic cores 1b, 1c are arranged at four locations symmetrically about the rotating shaft 5 of the rotor 4 at 90 degree intervals.

In addition, these coils 1a, 1d and magnetic cores 1b, 1c
are arranged at mutually corresponding positions on both end rings 6 of the rotor 4.

That is, one end ring 6 is provided with four locations, and the other end ring 6 is provided with four locations.

However, the number of disposed portions is not particularly limited, and any structure may be used as long as the disposed portions are disposed at two or more even numbers of locations on one end ring 6.

According to this embodiment, as shown in FIG.
Compared to the detected value by the conventional device shown in the figure, the secondary current of the induction motor was stably detected with less ripple.

〔Effect of the invention〕

As described above, the present invention can stably detect the secondary current of an induction motor with less ripple.

Therefore, the electric torque can be stably detected by multiplying the detection signal and the main magnetic flux detection signal.

Therefore, it is possible to stably use it for controlling an induction motor.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an embodiment of the present invention applied to an induction motor, Fig. 2 is a partial explanatory diagram of the embodiment of Fig. 1, and Fig. 3 is an explanatory diagram of a conventional device applied to an induction motor. , FIG. 4 is a partial explanatory diagram of the conventional device shown in FIG. 3, FIG. 5 is a graph of the secondary current detected value by the conventional device shown in FIG. 3, and FIG.
It is a graph of the next current detection value. 1...Sensor part, 1a, 1d...Coil, 1
b, 1c...Magnetic core, 2...Astable multivibrator, 3...Smoothing circuit, 4...Rotor, 5...
Rotating shaft, 6...end ring.

Claims (1)

[Scope of Claims] 1. A sensor section that is disposed opposite to an end ring of a rotor of an induction motor and is composed of a coil and a magnetic core made of a ferromagnetic material inserted into the coil;
an astable multivibrator connected to the coil that self-oscillates and outputs in response to the secondary current of the end ring; and a smoothing device that removes the alternating current component from the output from the astable multivibrator and outputs only the direct current component. In a secondary current detection device for an induction motor comprising a circuit, the sensor section comprises a plurality of coils connected in series or parallel to each other, and a magnetic core inserted into each of the coils, the coil and the 1. A secondary current detection device for an induction motor, characterized in that magnetic cores are arranged symmetrically about the rotational axis of the rotor, and are arranged at mutually corresponding positions on both end rings of the rotor.