JPS5822958B2 - induction motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction motor with particularly excellent servo performance.

As a control method for induction motors, so-called transformer vector control is used, which performs vector control by dividing the motor current into an excitation component current (reactive component) and an armature current component (torque component) that generates a magnetomotive force orthogonal to this component. Alternatively, techniques such as constant slip control have been developed to optimally control the frequency and control the speed of an induction machine to the same level as a DC machine.

However, a normal induction machine has only one set of stator windings, and when vector control is applied to this, a current corresponding to the vector sum of the excitation component current and the torque component current is passed. There is.

It is not appropriate to apply this method to, for example, an induction machine used as a servo motor for driving a high-density magnetic storage device that requires acceleration/deceleration performance of about 1 millisecond.

This is because in order to obtain good servo performance in this type of servo motor, the moment of inertia must be extremely small, and therefore the air gap must be several times larger than that of a normal induction motor. , Therefore, it is necessary to flow a correspondingly large excitation current.

In other words, a large-current excitation winding that can flow a large excitation current has a large leakage inductance, and if the excitation component current and torque component current are passed together in one stator winding, the torque component current If the servo motor is significantly affected by this, and if the servo motor is started and stopped frequently, the response of the torque component current will deteriorate significantly, making it impractical.

It is possible to use a high voltage power supply to compensate for the large reactance voltage drop caused by large leakage inductance, but this would reduce the power supply capacity.

The present invention has been made in consideration of this point, and an object of the present invention is to provide an induction motor with excellent acceleration/deceleration performance and speed control performance comparable to that of a DC machine.

To achieve this object, the present invention provides a stator core having a slot, an excitation winding housed in the bottom of the slot of the stator core, and an armature winding housed in the slot facing the air gap. , comprising a magnetic circuit closed core facing the stator core across an air gap, and a rotor made of a conductive thin plate supported so as to rotate in the air gap, the rotor having an average rotational speed of An excitation component current having a frequency including the slip component is supplied to the excitation winding, and a torque component current that generates a magnetomotive force orthogonal to the magnetomotive force by the excitation winding is supplied to the armature winding to generate a vector. This is a configuration of an induction motor that is controlled.

Hereinafter, the present invention will be explained in more detail based on embodiments shown in the drawings.

In the induction motor shown in Fig. 1, a cylindrical stator core 1
An excitation winding 3 is housed in the bottom of a slot 2 provided on the inner peripheral side of the armature winding 3, and an armature winding 4 is housed so as to overlap the excitation winding 3 and face the gap.

Inside the stator core 1, a cylindrical magnetic path closing core 5 is arranged concentrically and facing each other with an annular gap g in between.

A lightweight cup-shaped rotor 6 that can rotate in the gap g
is supported.

The rotor 6 is made of a conductive thin plate, and the material thereof is preferably aluminum or an aluminum alloy because of its low specific gravity and high conductivity.

This electric motor uses a lightweight cup-shaped rotor 6 to reduce the moment of inertia.

Therefore, the magnetic air gap is several times larger than that of a normal induction motor,
The excitation current also increases several times accordingly.

In order to flow this large excitation current, the cross-sectional area of the slot 2 is made large so that the excitation winding 3 for large current can be housed therein.

However, on the other hand, such a design increases the leakage inductance of the winding, as already mentioned.

When not only the excitation current but also the torque component current is passed through such a winding, the torque component current changes quickly, so a large voltage is required to compensate for the large actance voltage drop. capacity increases.

Therefore, according to the present invention, a winding exclusively for passing only the torque component current, that is, an armature winding 4, is separately provided near the air gap.

Even if there is a sudden change in the slip frequency, the excitation current changes continuously, so there is no need for a sudden change in the vector phase for vector control.

On the other hand, the torque component current requires a sudden change in phase.

This is because the change in magnetic flux must be continuous.

Furthermore, in the electric motor of the present invention, the armature winding 4 through which the torque component current flows and the rotor 6, ie, the secondary winding conductor, are close to each other, so that the magnetic coupling between them is good and secondary leakage flux is small.

When the secondary leakage flux is small, the linear range of torque becomes wide, and the adaptability of the servo motor is improved.

As shown in FIG. 2, the excitation winding 3 is supplied with an excitation component current 'm from the first inverter 7, and the armature winding 4 is supplied with a torque component current 'm from the second inverter 8. e is supplied.

As shown in Fig. 3, the locus of the magnetomotive force vector due to the excitation current 'm slowly curves in a circular arc at a rotation speed that is the average rotation speed of the rotor 6 (about 500 rpm for a normal magnetic storage device) plus slippage. The magnetomotive force vector due to the pulsed torque component current Ie at this -7 is a
-b-c, a'-b'-c'.

As already mentioned, since the armature winding 4 faces the air gap, the inductance can be made extremely small, so the capacity of the control power supply that flows the pulsed current can be small, saving space and reducing costs. useful for.

On the other hand, since the excitation winding 3 can generate a large magnetomotive force regardless of the inductance of the armature winding 4, the air gap magnetic flux density can be sufficiently increased.

In addition, during high-speed continuous operation, constant output speed sterilization is possible by controlling only the excitation winding current of 1 m.

The cup-shaped rotor made of aluminum has extremely low inertia, and by passing a large pulsed current through the armature winding 4, it can rapidly accelerate from 0 to full speed in about 1 millisecond, or vice versa, and suddenly stop. It becomes possible to fully satisfy the requirements of

As described above, in the induction motor according to the present invention, the stator winding is divided into the excitation winding and the armature winding, and the excitation winding is sufficiently stored at the bottom of the slot so that the air gap magnetic flux density can be sufficiently increased. At the same time, by storing the armature winding facing the air gap, the inductance can be extremely small, and the rise of the torque component current io can be made faster. The use of a rotor allows for high-grade servo control, such as driving a high-density magnetic storage device, in place of a high-performance DC machine, even though it is brushless.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of an induction motor according to the present invention, FIG. 2 is a connection diagram of a control circuit of the induction motor of FIG. 1, and FIG. 3 is a magnetomotive force vector diagram of the induction motor. DESCRIPTION OF SYMBOLS 1... Stator core, 2... Slot, 3... Excitation winding, 4... Armature winding, 5... Magnetic path closing iron core, 6
... Rotor, 7... First inverter, 8... Second inverter.

Claims (1)

[Claims] 1. A stator core having a slot, an excitation winding housed in the bottom of the slot of this stator core, an armature winding housed in the slot facing the air gap, and an armature winding placed across the air gap from the stator core. Comprising magnetic circuit closed iron cores facing each other and a rotor made of a conductive thin plate supported so as to be able to rotate in the air gap, an excitation component current having a frequency equal to the average rotational speed of the rotor plus a slip component. is supplied to the excitation winding, and a torque component current that generates a magnetomotive force orthogonal to the magnetomotive force by the excitation winding is supplied to the armature winding to perform vector control.