JPS6380792A - Variable speed motor - Google Patents

Abstract

PURPOSE:To continuously control the speed in a wide range by winding an exciting coil and a plurality of main coils on a stator so that the directions of magnetic fluxes do not coincide. CONSTITUTION:An exciting coil 5 and a plurality of main coils 3 and 4 are so wound on a stator that the direction of the magnetic flux formed by the coil 5 does not coincide with that of the magnetic fluxes formed by the coils 3 and 4. A pulsating current is fed by sequentially switching from an AC power source through a voltage regulator 8, a rectifier 7 and a conduction switching unit 9 to the plurality of the coils 3 and 4. Thus, a voltage is induced in a rotor conductor 6, and a current flows to the conductor 6. When a DC current flows to the coil 5 from a DC power source, a magnetic flux is generated by the current. A torque is generated at the rotor by the magnetic flux and the pulsating current flowing to the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a variable speed electric motor with good torque characteristics and efficiency and easy speed control.

Prior art and its problems One method of controlling the speed of an electric motor is to change the power supply frequency. Although this method allows continuous and wide-range speed control, the frequency converter required by this method is expensive, and the process of converting alternating current to direct current and then converting it back to alternating current with the frequency converter generally requires high-frequency adjustment. Waves and radio waves are generated, and these can cause problems such as malfunction of computers and their electrical control equipment or overheating of capacitors. Among these, harmonic interference can be countered by installing filters. However, installing filters is costly. Additionally, they have drawbacks such as generally insufficient performance at low speeds.

In addition, the method of controlling the speed by changing the number of poles of an electric motor, even though the speed can be changed step by step by changing the number of poles,
The disadvantage is that stepless and smooth speed control cannot be performed.

Further, in the method of controlling the speed by changing the voltage of the power supply, although the speed can be controlled continuously, there is a drawback that the efficiency is poor especially in the low speed region.

In wire-wound motors, the method of controlling the speed by changing the secondary resistance and changing the slip is relatively easy to control the speed continuously, but on the other hand, it is possible to control the rotor winding from the outside via brushes and slip rings. Inserting a resistor into the circuit requires maintenance and inspection due to brush wear, and squirrel cage induction motors have the disadvantage that speed control cannot be performed by changing the secondary resistance.

Additionally, DC motors have the disadvantage of requiring maintenance and inspection due to wear and tear on the brushes and commutator.

OBJECTS OF THE INVENTION An object of the present invention is to improve the drawbacks of the prior art described above, and to provide a variable speed electric motor that can perform speed control over a wide range and continuously, and has good torque characteristics and efficiency.

Means for Solving the Problems In order to achieve the above object, the present invention provides a stator facing the outer periphery of the rotor, and the stator has an excitation winding and a plurality of main windings connected to the excitation winding. The plurality of main windings are wound so that the direction of the magnetic flux produced by the main windings does not match the direction of the magnetic flux produced by the main windings, and the plurality of main windings are connected to an AC power source via an energization switching device, a rectifying device, and a voltage regulating device. The solution was to connect the excitation winding to a DC power source.

When a pulsating current is passed from an AC power supply through a voltage regulator, a rectifier, and an energization switching device to a plurality of main windings wound around the stator by sequentially switching, the pulsating current generates a similar magnetic flux. The magnetic flux induces a voltage in the rotor conductors,
Current flows through the rotor conductors. On the other hand, when a DC current is passed through the excitation winding wound around the stator from a DC power source, magnetic flux is generated by this current.

Here, each winding is wound so that the directions of the magnetic flux created by the main winding and the magnetic flux created by the excitation winding do not match, so torque is generated by the magnetic flux created by the excitation winding and the current flowing through the rotor conductor. The rotor rotates. By the way, when a pulsating current is caused to flow from an AC power supply by sequentially switching to a plurality of main windings wound around a stator through a voltage regulator, a rectifier, and a current switching device, a constant current is applied from the moment when the pulsating current starts flowing. For a short time, pulsating current flows in the rotor conductors due to transient phenomena.

Therefore, if the energization switching device sequentially switches and energizes each of the plurality of main windings to cause a pulsating current to flow through the rotor conductor, the magnetic flux due to the DC current flowing through the excitation winding and the pulsating current flowing through the rotor are generated. Torque is generated in the rotor and it continues to rotate.

The magnitude of the current flowing through the main winding is controlled by adjusting the output of the voltage regulator, and the speed of the rotor can be controlled by adjusting the magnitude of the current flowing through the excitation winding as necessary.

Example Embodiments of the present invention will be described with reference to FIGS. 1 to 5.

As shown in FIG.
Two main windings 3 and 4 and an excitation winding 5 are wound around the stator 1. The position of the main winding 3 or 4 on the stator and the excitation winding 5 so that the magnetic flux produced by the main winding 3 or 4 and the magnetic flux produced by the excitation winding 5 are 90 degrees in electrical angle. The wires are wound so that the position on the stator is 90° electrically.

The rotor conductor 6 attached to the rotor 2 short-circuits all the rotor conductors at both ends of the rotor in the axial direction in a squirrel cage rotor. Alternatively, a wire-wound rotor may be used.

Next, as shown in FIG. 2, the main winding 3. The main winding 4 is connected to an AC power source through a current switching device 9, a rectifier 7, and a voltage regulator 8. The energization switching device 9 is switched to switch the main winding 3 to the third
When a pulsating current 11 is passed as shown in the figure, this pulsating current 1
1, a magnetic flux φ1 similar to the pulsating current 11 is generated, and this magnetic flux φ1 causes a pulsating current In similar to the magnetic flux φ1 to flow in the rotor conductor 6 as shown in FIG.

On the other hand, the excitation winding 5 is connected to the DC power supply through the variable resistor 10.
When a DC current I2 is applied to the magnetic flux φ2, a magnetic flux φ2 is generated by this current. Here, the positions of the main winding 3 and the excitation vA winding 5 on the stator differ by 90 degrees in electrical angle, so the magnetic flux φ2 is the magnetic flux φ1
orthogonal to

Torque is generated by this magnetic flux φ2 and the current In flowing through the rotor conductor 6, and the rotor 2 rotates.

By the way, as shown in FIG. 5, there is a transient phenomenon in which a pulsating current flows through the rotor conductor 6 for a short time from the moment when the pulsating current 11 starts flowing through the main winding 3, but changes to an alternating current as time passes. Once the current is switched to alternating current, it is no longer possible to generate torque using the magnetic flux φ2 and the current 1o flowing through the rotor conductor. Therefore, a pulsating current 11 is passed through the main winding 3 for a short time, and while the pulsating current 10 is flowing through the rotor conductor, the current flowing through the main winding 3 is cut by the energization switching device 9, and the pulsating current is passed through the main winding 4. Switch so that current flows. When a pulsating current is passed through the main winding 4, the pulsating current flows through the rotor conductor 6 due to a transient phenomenon for a short period of time at the beginning of the current, similar to when it is passed through the main winding 3. Therefore, the magnetic flux φ2 and the main winding 4 Rotor conductor 6 by
Torque is generated by the pulsating current, and the rotor 2 rotates.

The main winding 3 is sequentially switched by the energization switching device. When a pulsating current is passed through the main winding 4, the pulsating current flows through the rotor conductor 6, generating torque with the magnetic flux φ2 and continuing to rotate. If the timing of switching the energization to the main winding 3 and the main winding 4 is set appropriately, a corresponding torque can be obtained.

Further, the magnitude of the current flowing through the main winding 3 or the main winding 4 can be controlled by adjusting the output voltage using the voltage regulator 8. Further, the current flowing through the excitation winding 5 can be changed by changing the size of the resistor 10 or by adjusting the size of the output voltage of the DC power supply.

In this way, the speed of the rotor 2 is controlled by adjusting the magnitude of the current flowing through the main winding 3 or 4 and the current flowing through the excitation winding.

In the embodiment of the present invention, the direction of the magnetic flux produced by the main winding 3 or 4 and the magnetic flux produced by the excitation winding 5 is 9 in electrical angle.
0', the main winding 3 or 4 is wound so that the position on the stator and the position of the excitation winding 5 on the stator are 90 degrees in electrical angle. It is sufficient that the directions of the magnetic flux produced by the main winding 3 or 4 and the excitation winding 5 do not match, and the positions of the main winding and excitation winding on the stator can be appropriately selected. characteristics are obtained.

Effects of the Invention The variable speed motor of the present invention has no brushes, so maintenance is easy, and although a rectifier is used, it does not require a smoothing circuit to create a DC voltage with less pulsation, unlike a general rectifier. Since the pulsating flow is used as it is, there are fewer harmonics.

Also, since the variable speed motor of the present invention has characteristics similar to those of a DC motor, is it possible to use induced lightning? ! Unlike the 71s, the rotational speed is not limited to the synchronous speed or lower, and high-speed rotation is possible, and the starting torque is also large. It also has no slip loss like induction motors and is highly efficient.

[Brief explanation of the drawing]

Figures 1 to 5 are embodiments of the present invention. Figure 1 is a cross-sectional explanatory diagram showing the relationship between the stator and rotor, Figure 2 is a system configuration diagram, and Figure 3 is the direction of magnetic flux. FIG. 4 is an explanatory diagram of the rotor structure and current flow, and FIG. 5 is an explanatory diagram of the transient phenomenon of transition of pulsating current to alternating current.

Claims (2)

[Claims] (1) A stator is provided facing the outer periphery of the rotor, and the stator has an excitation winding and a plurality of main windings arranged in the direction of the magnetic flux produced by the excitation winding and the direction of the magnetic flux produced by the main winding. The windings are wound so that the directions do not match, and the plurality of main windings are connected to an AC power source via an energization switching device, a rectifier, and a voltage regulator, and the excitation winding is connected to a DC power source. A variable speed electric motor characterized by: (2) The main winding and the excitation winding are wound around the stator so that the direction of the magnetic flux created by the main winding and the direction of the magnetic flux created by the excitation winding are 90 degrees in electrical angle. A variable speed electric motor according to claim (1).