JPS6395888A - Variable-speed motor - Google Patents

Abstract

PURPOSE:To increase the torque in a low-speed region and to improve the efficiency, by causing the rectified current to flow to a rotor by means of diodes interposedly provided to rotor conductors. CONSTITUTION:Diodes 8 and 9 are interposedly provided at rotor conductors, so that the current rectified in half-wave flows to the rotor conductors. Consequently, it is hard for the rotor conductors to be affected by the inductance and the current is prone to flow to the rotor conductors. The power factor is therefore improved as compared with the case where AC current is caused to flow, and the torque in low-speed region increases. When a rotor rotates, the polarity of DC distributed current contained in the short current is alternated in every half a rotation and the stator winding produces a rotating magnetic field in proportion to the rotating speed of the rotor. On this account, the torque by the rotating field where the power source frequency is at synchronized speed and the torque by the rotating field in proportion to the rotating speed are overlapped, so that the total torque is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 frequency. Although this method allows continuous, targeted 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 using the frequency converter is generally difficult. Harmonics and radio waves are generated, which can cause malfunctions in computers and other electrical control equipment, overheating of capacitors, and other problems. Among these harmonics, countermeasures can be taken by installing filters. However, installing filters is costly. Additionally, they generally have drawbacks such as 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.

[Object of the invention] An object of the present invention is to improve the drawbacks of the above-mentioned prior art and 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 Problem) A stator is provided facing the outer periphery of the rotor, and a rotor groove is provided between the rotor and the rotor winding or the rotor conductor at an arbitrary electrical angle of the rotor. A set of diodes or a plurality of diodes of the same polarity connected in series are interposed in each winding or conductor attached to the stator, and a voltage regulator is connected to the winding wound around the stator. This was the solution.

[For production]

When current is passed from an AC power supply through a voltage regulator and a phase shifter to at least two windings wound around the stator, the rotor windings or rotor conductors are interposed with diodes. A half-wave rectified current flows through the conductor or rotor winding, and an alternating current having a waveform in which a direct current component is superimposed on the half-wave rectified current flows through the stator winding. This DC component current is larger than the normal excitation current.

The magnetic flux created by the stator windings and the current flowing through the rotor windings or rotor conductors generate torque, causing the rotor to rotate.

By the way, since diodes are interposed in the rotor windings or rotor conductors, a half-wave rectified current flows through the rotor windings or rotor conductors, and therefore the rotor windings are less affected by inductance. Or current tends to flow through the rotor conductors.

Therefore, compared to the case where alternating current is passed, the power factor is improved and the torque in the low speed region is increased.

Further, when the rotor rotates, the polarity of the DC component current included in the stator current alternates every half rotation, and the stator winding creates a rotating magnetic field proportional to the number of rotations of the rotor.

This rotating magnetic field is different from a rotating magnetic field whose speed is synchronous with the power supply frequency. Further, the strength of the rotating magnetic field proportional to the rotation speed is greater than the strength of the rotating magnetic field whose synchronous speed is the power supply frequency.

Since the rotating magnetic field proportional to the rotational speed is equal to the rotational speed of the rotor, no new current flows through the rotor conductor or rotor winding due to this rotating magnetic field, but the rotor conductor or rotor winding Torque is generated between the rectified current flowing through the Therefore, since the torque due to the rotating magnetic field with the power supply frequency as the synchronous speed and the torque due to the rotating magnetic field proportional to the rotational speed are superimposed, the torque becomes large and the efficiency becomes high.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 to 4.

As shown in FIG.
In a squirrel cage rotor, the rotor conductor 5 attached to the rotor 2 has two windings 3 and 4 wound around the stator 1. Short circuit the conductor. Alternatively, a wire-wound rotor may be used.

Next, winding 3 is connected to a phase shifter and voltage regulator, and winding 4 is connected to an alternating current power supply via a voltage regulator. In addition, as shown in Fig. 4, the rotor has diodes 8 of the same polarity interposed in each conductor between the electrical angles of 0° and 180°, and between the following electrical angles, Diodes 9... are interposed in each conductor with opposite polarity.

Although FIG. 4 shows an example of two poles, other numbers of poles may be used. When current is applied from an AC power source to the winding 3 through the voltage regulator 6 and the phase shifter 7, and to the winding 4 through the voltage regulator 7, the stator winding 3 and Currents [1 and 2] flow through the stator winding 4, respectively, and these currents It and 12 generate similar magnetic fluxes φ1 and φ2, and these magnetic fluxes cause currents to flow in the rotor conductors. Here, since the stator windings 3 and 4 are shifted in phase by 90 degrees in electrical angle by a phase shifter provided in the stator winding 3, the magnetic flux φ1 is orthogonal to the magnetic flux φ2. by the way,
Since the rotor conductor is provided with a diode as described above, a half-wave rectified current flows through the rotor conductor, and a DC component of the half-wave rectified current flows through each winding 32 and winding 4. An alternating current with a superimposed waveform flows.

This DC component current is larger than the normal excitation current. and stator winding 3. The magnetic flux created by the stator winding 4 and the current flowing through the rotor conductors shown in FIG. 4 generate torque, causing the rotor to rotate.

By the way, since the rotor conductor is equipped with a diode as shown in Figure 4, a half-wave rectified current flows through the rotor conductor, so it is less affected by inductance, and the rotor conductor has a diode. Easy to flow. Therefore, the power factor is better than when an alternating current is passed, and the torque in the low speed region is increased. Further, when the rotor rotates, the polarity of the DC component current included in the stator current is alternated every half rotation, and the stator windings 3 and 4 create a rotating magnetic field proportional to the rotation speed of the rotor. This rotor magnetic field is different from a rotating magnetic field whose synchronous speed is the power supply frequency. Further, the strength of the rotating magnetic field proportional to the rotation speed is greater than the strength of the rotating magnetic field whose synchronous speed is the power supply frequency.

Since the rotational speed of the rotating magnetic field, which is proportional to the rotation speed, is equal to the rotational speed of the rotor, no new current flows through the rotating conductor due to this rotating magnetic field.

In the embodiment of the present invention, the winding 3 and the winding 4 are provided, and the phase of the current is changed by a phase shifter so that the direction of the magnetic flux produced by them becomes 90 degrees in electrical angle.
It is not limited to .degree., and appropriate characteristics can be obtained by appropriately selecting the phase. Further, the number of windings is not limited to two, but may be three or more.

Further, although the embodiments have been described using squirrel cage rotor conductors, a wire-wound type may be used.

(Effects of the Invention) Since the variable speed motor of the present invention has no brushes, maintenance is easy, and the power frequency can be adjusted by passing rectified current through the rotor using diodes inserted in the rotor conductor or rotor winding. Since the torque due to the rotating magnetic field at a synchronous speed and the torque due to the rotating magnetic field proportional to the rotational speed are superimposed, the torque increases and efficiency improves.

[Brief explanation of the drawing]

Figures 1 to 4 show examples 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 diodes interposed in the rotor conductors. 1...Stator 2...Rotor 3.4...
・Winding 5...Rotor conductor 6...Voltage regulator 7...Phase shift device 8.9...Diode

Claims (3)

[Claims] (1) A stator is provided facing the outer periphery of the rotor, and each stator is installed in a rotor groove for installing rotor windings or rotor conductors between arbitrary electrical angles of the rotor. Variable speed characterized in that one diode or a plurality of diodes of the same polarity connected in series are interposed in the winding or the conductor, and a voltage regulator is connected to the winding wound around the stator. Electric motor. (2) The variable speed electric motor according to claim (1), wherein the arbitrary electrical angle is an electrical angle of 180° or less. (3) The winding or conductor to be wound in the rotor groove for installing the rotor winding or rotor conductor during the next arbitrary electrical angle following the above-mentioned arbitrary electrical angle has the above-mentioned one. or a plurality of diodes of the same polarity connected in series, and one diode or a plurality of diodes of the same polarity connected in series with the opposite polarity are interposed.
The variable speed electric motor described in item 1).