JPH01248994A - Variable speed induction motor - Google Patents

Abstract

PURPOSE:To enable continuous setting of speed control zone over a wide range by providing a voltage phase shifter for shifting the phase of one of a plurality of stators facing to a plurality of rotor cores from those of other stators and providing a voltage regulator for the stator winding. CONSTITUTION:A plurality of conductors 5 arranged in rotor cores 2, 3 mounted on a rotor shaft 4 with a random interval are connected in series, thus forming a rotor 8. Respective conductors 5 are shortcircuited through resistive members (r) at a non-magnetic core section 9 between the rotor cores 2, 3. On the other hand, stators 24, 25 are juxtaposed to a machine frame 14 on the outer circumference facing to the rotor cores 2, 3. Motor torque is controlled by regulating the phase difference between the stator 25 and the fixed stator 24 through a voltage phase shifter 38. Furthermore, a voltage regulator for regulating the voltage to be applied onto the windings of the stators 24, 25 is provided.

Description

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

Prior art and its problems One method of controlling the speed of an induction motor is to change the power supply frequency. Although this method allows for 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 the computer and its electrical control equipment or overheating of the capacitor. Among these, harmonic interference can be countered by installing a filter. However, installing filters is costly. Additionally, they have drawbacks such as generally insufficient performance at low speeds.

Furthermore, the method of controlling the speed by changing the number of poles of the electric motor has the disadvantage that even if the speed can be changed stepwise by changing the number of poles, it is not possible to control the speed steplessly and smoothly.

Further, although the method of controlling the speed by changing the voltage of the power supply allows the speed to be controlled continuously, it has the disadvantage that the efficiency is poor especially in the low speed range.

In wire-wound motors, the method of controlling speed by changing the secondary resistance and changing the slip allows continuous speed control relatively easily, but it also allows the rotor to be wound externally via brushes and slip rings. Inserting a resistor into the line circuit requires maintenance and inspection due to brush wear, and the squirrel type induction motor has the problem that speed control cannot be performed by changing the secondary resistance.

To address the above problems, for example,
The technology is disclosed in Publication No. 29005, which includes a squirrel-cage conductor that is commonly installed across two sets of rotor cores and short-circuited at both ends via short-circuit rings, A high-resistance element short-circuiting the squirrel-cage conductors at the center of the squirrel-cage conductors between the two sets of rotor cores, and windings on independent stators facing the rotor cores, At startup, the phase between the stator windings is set to 18
This is a twin iron core squirrel cage movable rock that supplies power in phase with each other during operation after startup, but by shifting the phase of the stator windings by 180 degrees during startup, the starting torque is increased and the starting torque is increased. The characteristics are improved and the stator windings are matched in phase with each other during operation so that the motor can be operated with normal torque characteristics.

Therefore, even if the effect of improving startability is recognized, this electric motor is not a variable speed electric motor and cannot be used as a power source for a load that requires speed change.

Furthermore, JP-A-49-86807 proposes an asynchronous electric motor having a stator with polyphase windings and a squirrel-cage rotor, which consists of conducting bars, short-circuit end points, and ferromagnetic laminations. In which the stator consists of first and second winding sections, which sections are coaxially arranged adjacent to each other and to different parts of the rotor and are supplied with an alternating current of the same frequency. an asynchronous electric motor capable of altering the electromotive force induced in the rotor windings by means of a second winding section; Although it is possible to change the rotation speed by creating a phase difference between the stator sections, the torque is small unless the phase angle between the two stator sections is in the same phase, and the operation stops immediately when a load is applied. It was completely unsuitable for practical use due to its flaws, and the serious problem of not being able to operate it as a power source that requires frequent starting and stopping when a load is connected remains unresolved.

Purpose of the Invention The present invention is intended to improve the drawbacks of the above-mentioned prior art, and seeks excellent torque characteristics.The present invention is intended to improve the above-mentioned drawbacks of the prior art. It is an object of the present invention to provide a variable speed induction motor which can be set and started with any torque, and which has excellent torque characteristics and efficiency over the entire speed range from the starting point to the maximum rotational speed.

The variable speed induction motor of the present invention is used by being connected to a single-phase or three-phase power source, and the rotor has a normal squirrel cage type, a double squirrel cage type, and a deep groove squirrel type.

It can be applied to any type of special squirrel-cage rotor core, etc., and the conductor used in the explanation of the present invention refers to a conductor installed in a squirrel-cage rotor core and a conductor wound around a wound rotor core. This is a general term for each of the windings installed.

Means for Solving the Problems In order to achieve the above technical problem, the present invention connects each of a plurality of conductors installed in each of a plurality of rotor cores to form an integral rotor. A plurality of stators are arranged in parallel on the machine frame on an outer peripheral portion facing the plurality of rotor cores which are formed and mounted on the same rotating shaft at arbitrary intervals, and are opposed to the plurality of stators. Each of the plurality of conductors is short-circuited via a resistive material between the plurality of rotor cores that are not connected to each other, and the plurality of conductors are A phase difference is created between the voltage induced in the conductor portion of the rotor facing one of the stators and the voltage induced in the corresponding conductor portion of the rotor facing the other stator. In order to solve the problem, a voltage adjusting device was attached to the windings of the plurality of stators, and a voltage adjusting device was attached to the windings of the plurality of stators.

Effect of the present invention: When a phase shift is caused in the magnetic flux of the rotating magnetic field generated between the respective stators by an arbitrary means, the combined voltage induced in the rotor conductor changes in accordance with the phase shift of the magnetic flux. The rotational speed of the rotor can be arbitrarily changed by controlling the increase/decrease of the combined voltage induced in the rotor conductors.

By the way, by short-circuiting a plurality of conductors installed in a plurality of rotor cores via a resistor material, the magnitude of the current flowing through the resistor material is controlled by the phase difference θ, and excellent torque characteristics can be achieved. However, as will be explained in detail later, if the resistance value of the resistance material is made too large, the torque characteristics will deteriorate, so the resistance value of the resistance material is made relatively small, and as a result, the variable speed range is limited. This narrowing can now be compensated for by a voltage regulator, making it possible to create a variable speed induction motor with good torque characteristics and a wide variable speed range.

Example Embodiments of the present invention will be described based on FIGS. 1 to 8.

An embodiment of the present invention will be described with reference to FIGS. 1 to 4. Referring to FIGS. 1 and 3, reference numeral 1 indicates an induction motor, and the induction motor 1 is constructed as follows. Rotor cores 2.3 made of iron cores are mounted on the rotor shaft 4 with arbitrary intervals, and a non-magnetic core 9 is interposed between the rotor cores 2.3. A plurality of conductors 5 installed in the rotor core 2.3 are connected in series to form an integrated rotor 8.
, and both ends of the plurality of conductors 5 connected in series are connected to a short circuit ring 6.7. In addition, a plurality of ventilation bodies 11i112... are provided in the rotor core 2.3.9, which communicate with both sides 10.11 of the rotor 8, and ventilation barrels 12...
- A plurality of ventilation holes 13 are bored perpendicularly through the outer periphery of the rotor 8. The rotor 8 has a plurality of conductors 5 in the non-magnetic core 9 between the rotor cores 2.
When a current with an arbitrary vector difference flows through each of the resistive materials "...", they are short-circuited through nichrome wire, carbon-containing steel, conductive ceramic, etc. (1st
2) Bearing discs 15 and 16 provided on both sides of the cylindrical machine frame 14 are connected to connecting rods 17 and nuts 18...
Cooling impellers 19 and 20 are attached to both sides of the rotor 8, and both ends of the rotor shaft 4 are attached to the bearing plate 1.
The rotor 4 is supported by a bearing 21.21 fitted in the rotor 4.
It is rotatable.

A first stator 24 and a second stator 25, each having a winding 22.23 on the outer side facing the rotor core 2.3, are arranged side by side on the machine frame 14, and the machine frame 14 and the first stator 24. A sliding bearing 26.27 is installed between the second stator 25 and the sliding bearing 26.27.
27 is fixed by a stop ring 28 fitted to the machine frame 14, and gears 33A and 33B are fitted to the negative side outer peripheral surfaces of the first stator 24 and the second stator 25. (Second
(See Fig. 3) A driving gear 36 is pivotally attached to a pulse motor 35 fixed to the outer periphery of the machine frame 14, and the relay shaft 29 is rotatable on a bearing stand 32 attached to the outer side of the machine frame 14. The relay gear 3o and the rotation gear 31 are mounted on both ends of the relay shaft 29, and the drive gear 36 and the rotation gear 31 are inserted through the openings 37 and 37 provided in the machine frame 14. The rotating gear 31 is inserted into the machine frame 14 and engaged with the gear 338 fitted to the second stator 25, and the driving gear 36 is inserted into the first stator 24.
The relay gear 3 is engaged with the gear 33A fitted on the drive gear 36, and the interlocking gear 34 is integrally formed with the drive gear 36.
0, the first stator 24 and the second stator 25 are configured to be rotatable concentrically with the rotor 8, and the voltage phase is shifted by the first stator 24 and the second stator 25. The device 38 is formed with a variable speed continuous electric motor. 39 is an exhaust hole, and 40 is a plurality of ventilation holes bored in the bearing plate 15, 16.

The operation of the above configuration will be explained below.

When the windings 22 of the first stator 24 are energized from a commercial three-phase power supply, a rotating magnetic field is generated in the stator 24.25, voltage is induced in the rotor 8, and current is generated in the conductors 5 of the rotor 8. The flow causes the rotor 8 to rotate.

When the amount of rotation of each second stator 25 with respect to the first stator 24 is set to zero, each stator 24.25
Since there is no phase shift in the magnetic flux of the rotating magnetic field generated in the motor, and no current flows through the resistor material r, as will be described in detail later, the motor has the same torque characteristics as a general induction motor.

Next, a case will be described in which the pulse motor 35 is operated to rotate the first stator 24 and the second stator 25 in opposite directions by a phase angle of θ. Voltage phase shifter 3
The magnetic flux φ1.8 of the rotating magnetic field created by the first stator 24 and the second stator 25. The phase of φ2 is shifted by θ, and therefore the phase of the voltages tA+, 62 induced by the first stator 24 and the second stator 25 in the conductors 5, . . . of the rotor 8 is shifted by θ. Now, with the voltage I:32 induced by the second stator 25 in the conductor 5 of the rotor 8 as a reference, this voltage is set as ta2=SE. Here S is slipping, E
is the induced voltage when the slip is 1. At this time, the voltage white induced in the conductor 5A by the first stator 24 is 6+
=SEεjO.

What is shown in Fig. 4 shows the slip S of the rotor 8 and the rotor input when the resistive material r... that short-circuits the plurality of conductors 5... is not installed in the non-magnetic core 9 section. This shows the relationship with active power P. When the voltage phase is θ=O°, active power P is maximum, and when 0″<θ<180″, it is smaller. Here conductor 5...
Let the resistance and inductance of
/ωL).

Since the active power P is proportional to the driving torque of the induction motor 1, the rotor 8 is rotated by operating the pulse motor 35 to rotate the first stator 24 and the second stator 25 of the voltage phase shifter 38. By adjusting the voltage induced in the rotor, the speed of the rotor can be controlled steplessly.

Next, let R1 and R2 be the respective resistances from the short-circuit rings 6.7 of the conductors 5 of the rotor 8 to the connecting members, let Ll and L2 be the inductances, let ω be the angular frequency of the power supply, and let each conductor 5 . . , the electrical equivalent circuit of the rotor 8 is as shown in FIG. 5, and the symbols 11, 'I2, . I3 indicates the current flowing through each branch.

Next, when converting the circuit shown in Fig. 5 into an equivalent circuit viewed from both stator 24 and 25 sides, it becomes as shown in Fig. 6, and RI=R
2. When LI=L2 and θ=0°, 13=11-12
= 0, and no current flows through the resistor material r.

This means that when θ = 00, the torque T is equal to the value when there is no torque. Therefore, when θ = 0°, it has the same torque characteristics as a conventional induction S motor. .

Next, when RI=R2, Ll=L2 and θ=180°, II=-12, 1:1=II-12=211, and in the conventional induction motor, the resistance of the rotor conductor is RI
If =R2=R, the result is the same as if R were increased to R+2r.

As the rotor 8 rotates, outside air is sucked into the machine frame 14 by the cooling impellers 19 and 20 through the ventilation holes 40 formed in the bearing discs 15 and 16, and the cooling impellers 19 and 20 1st. The second stator 24° 25 and the windings 22, 23 are ventilated and cooled, and the ventilation holes 13...
・Rotor cores 2, 3, conductor 5...
・Resistance material r... etc. are cooled to stably perform their respective functions. Also, 1st. The second stator 24, 25 is rotated by rotating the pulse motor 35 in forward and reverse directions using a switch, but this is not limited to the pulse motor 35, and other forward and reverse rotation motors may also be used. It is possible to use any drive device such as a servo mechanism, etc., and there are cases in which it is operated by a manual handle and in which only one of the first stator 24 and the second stator 25 is rotated. The rotation of the stator is then released or locked by an arbitrary actuation mechanism in conjunction with the operation of the stator rotation drive device.

When each of the windings 22 and 23 of the first stator 24 and the second stator 25 are connected in parallel to a commercial three-phase power supply,
Winding I of stator 24 and second stator 25! i12.2.23
The voltages input to the stators 24, 25 are the same, and the voltages induced from each of the stators 24, 25 to the conductors 5... of the rotor 8 are the same, but the phases of the voltages differ by Pθ, and the voltages induced in the conductors 5... of the rotor 8 are the same.
・The current flowing through the resistive material r... is (1/
2) The current becomes approximately proportional to x (differential voltage induced in the rotor conductor from each of the first and second stators)÷(resistance value of the resistance material r...). However, in addition to the current flowing through the resistance material r... in the conductor 5 of the rotor 8 (first
．． A current approximately proportional to (sum voltage induced in the rotor conductor of the second stator)/(impedance of the rotor conductor) flows in a superimposed manner. (The above sum voltage is such that Pθ=π is zero and Pθ=
(The impedance of the rotor conductor is determined by the resistance of the conductor and the secondary leakage reactance, and therefore varies depending on the slippage.) Therefore, the impedance of the rotor conductor 5
For the magnitude of the current flowing in..., multiple conductors 5...
・The ratio of the current flowing through the resistive material r... between P
Even if θ is constant, it varies depending on the slip and resistance value, and P
The slip and torque characteristics when θ is constant are a mixture of the characteristics when the secondary insertion resistance of a general wound induction motor is constant and the characteristics when the primary voltage of a general induction motor is controlled. Becomes a characteristic.

FIG. 7 shows the torque characteristics in the embodiment of the present invention, and when the load torque is T, the variable speed range is from Sl to 82. Figure 8 is a torque characteristic diagram when the resistance value of the resistance material is larger than that in Figure 7. The intersection of the torque curve with the vertical axis of slip $ = 1 at θ = 180° is lower, that is, the starting torque is smaller. Therefore, the starting current can also be suppressed.

Further, when the load is a fan, a pump, etc., which has a square law reduction torque characteristic, the variable speed range is rather wider than in the case of FIG. 7.

By the way, the increasing tendency of the torque curve as it goes from S=0 to S=1 is inferior to the case shown in FIG. The variable speed range becomes narrower.

The variable speed induction motor of this configuration has different torque characteristics from a general so-called wound-rotor motor having a wound rotor in which a secondary resistance is inserted through a brush and a slip ring.

That is, in the case of the above-mentioned wound type electric motor, the secondary resistance is inserted in series with the rotor winding and exhibits a so-called proportional transition torque characteristic, but in the case of the variable speed induction motor of the present invention, the resistance material is inserted in the rotor conductor. When the resistance material is inserted in parallel and the resistance value of the resistance material is large, the torque characteristic becomes different from the proportional transition torque characteristic as described above.

The reasons for this are as follows. That is, by providing a phase difference θ, a phase shift occurs between the voltage induced in the portion of the rotor conductor corresponding to the stator on one side and the portion of the rotor conductor corresponding to the stator on the other side, Due to this, a current flows to the resistive material, and if the resistance value of the resistive material is large, the equivalent reactance increases, resulting in a result equivalent to a deterioration of the power factor, and the torque characteristics deteriorate.

The present invention has been made based on the discovery of the above-mentioned new fact. In other words, the resistance value of the resistance material should not be too large, but in that case, the intersection of the slip S = 1 with the vertical axis at θ = 180° will be at a high position, which means that the starting torque will increase and the starting current will also increase. .

In addition, the speed change range becomes narrow relative to the load.

In order to compensate for this, a voltage regulator 41 is attached to the stator winding to supply power from the power source. In short, the present invention aims to provide excellent torque characteristics by making the resistance value of the resistive material that shorts the rotor conductors between the rotor cores relatively small, expand the variable speed range, and reduce the starting torque. However, a voltage regulator was attached to the stator winding to reduce the starting current.

In addition, in FIGS. 7 and 8, the example in which multiple stator windings are connected in parallel to the power source is explained, but the example in which multiple stator windings are connected in series and connected to the power source is explained. The same thing can be said when connected.

Figure 9 is a connection diagram when the stator windings are connected to the power supply in parallel, but the stator windings may be connected in delta connection, and the stator windings may be connected in delta connection. In some cases, the windings are connected in series and connected to a power supply via a voltage regulator 41.

Note that the voltage regulator 41 may be any device as long as it achieves the object of the present invention, and a voltage regulator that uses a thyristor and can adjust the voltage in a stepless manner is used.

When the plurality of stators are connected in parallel, compared to when they are connected in series, the ratio of the current flowing through the rotor conductor and the current flowing through the resistive material is controlled by the phase difference θ, regardless of slip. However, the current flowing between the plurality of conductors 5 through the resistive material r is (
1/2) × (difference in voltage induced in the rotor conductor from each of the first and second stators) ÷ (resistance value of the resistive material r) The current is approximately proportional to the following: For example, in the case of a load with constant torque characteristics. The range of control becomes narrower.

If there is a space or a non-magnetic material between the rotor cores, the leakage reactor is reduced, and the variable speed induction motor becomes more efficient.

The voltage phase shifting device is not limited to the above-mentioned embodiment, and any device that generates a phase shift between the inner stators can be selected and implemented.

The voltage phase shifting device is a phase switching switch connected to a winding wound around at least one stator among the plurality of stators, and the voltage phase shifting device is connected to a single-phase transformer. It also includes one formed by a changeover switch, and one in which the voltage phase shift device is an induced voltage regulator. Also,
Each of the plurality of stators may be provided with a winding forming a plurality of types of pole numbers, and a pole number changeover switch may be connected to the terminal of the winding. In some cases, the connection of the windings wound around each of the coils can be freely switched to either delta connection or star connection to provide diversity in torque characteristics.

Furthermore, the variable speed induction motor of the present invention can also be used as an induction generator, and if a turbine or the like is directly connected to the rotor shaft 4 to generate electricity, an expensive governor can be omitted. In addition, when an internal combustion engine is connected as the prime mover, it can correspond to the rotation speed of the internal combustion engine with the minimum fuel consumption, and the power that uses feng shui as an energy source is weak and inefficient.

Even in stable conditions, power can be generated at the rotational speed that produces the maximum output, and in hydroelectric power generation, power can be generated efficiently according to the flow velocity, and complicated and expensive variable pitch devices or phase adjusters can be omitted. Furthermore, synchronization with external power can be performed without an expensive synchronization device. Then, if a switch is provided that connects another rotating shaft to the rotor shaft and switches the two phases on the input side of the stator winding, and the rotor shaft can be freely rotated in the forward and reverse directions by the switch, the switch By operating with a voltage phase shifter, it can also be used as an electric brake, and by controlling the rotational speed with the voltage phase shifter, the braking force of the rotating shaft connected to the rotor shaft can be efficiently adjusted.

In addition, when starting the electric motor of the present invention, the phase difference is set to 180° or an appropriate difference to suppress the starting power source, and the motor is started with high torque characteristics, and when it is operated, the phase difference is set to 0° or small. Needless to say, it can be used as an improved electric motor.

In addition, when the rotor is a wound type, the terminals of the windings wound around each of a plurality of rotor cores are connected for each phase to form an integral rotor winding. Each phase of the rotor winding is short-circuited via a resistive material.

Effects of the Invention As explained above, according to the present invention, a plurality of stators are arranged in parallel on a machine frame, a voltage phase shifter is connected to at least one of the stators, and the stator and Since each of the plurality of conductors is short-circuited through a resistive material between the rotor cores that do not face each other, all that is required is to operate the voltage phase shifter to create a phase shift in the magnetic flux of the rotating magnetic field generated in the stator. The rotation speed of the rotor can be changed arbitrarily by simple operation.

In addition, a voltage regulator is attached to multiple stator windings,
I connected it to the power source and supplied power through it, so
Even if the resistance value of the resistance material is made relatively small to improve the torque characteristics, it is now possible to widen the variable speed range and to set the starting current and starting torque to a small value or arbitrarily.

[Brief explanation of the drawing]

1 to 9 are illustrations of embodiments of the present invention. Figure 1 is a side sectional view of the induction motor, Figure 2 is a side view showing the stator rotation mechanism, Figure 3 is a partially cutaway side view showing the stator rotation mechanism, and Figure 4 is a side view showing the stator rotation mechanism. A diagram showing the relationship between rotor slip and active power, Figure 5 is an electrical equivalent circuit diagram of the rotor, Figure 6 is an electrical equivalent circuit diagram seen from the stator side, and Figure 7 is the resistance value of the resistive material. Torque curve when is relatively small,
FIG. 8 shows a torque curve when the resistance value of the resistive material is relatively large, and FIG. 9 shows an embodiment in which a voltage regulator is interposed between the power source and the stator winding.

Claims (3)

[Claims] (1) A plurality of conductors installed in each of a plurality of rotor cores are connected to form an integral rotor, and the plurality of conductors are connected to the same rotating shaft at arbitrary intervals. A plurality of stators are arranged in parallel on the machine frame on the outer periphery facing the plurality of rotor cores, and each of the plurality of conductors is arranged between the plurality of rotor cores that do not face the plurality of stators. a conductor portion of the rotor that is short-circuited through a resistive material, and that faces one of the plurality of stators in relation to at least one stator among the plurality of stators. A voltage phase shifter is provided to create a phase difference between the voltage induced in the rotor and the voltage induced in the corresponding conductor portion of the rotor facing the other stator, and the windings of the plurality of stators are A variable speed induction motor characterized by having a voltage regulator attached to the line. (2) The variable speed induction motor according to claim (1), wherein a space or a non-magnetic material is provided between the rotor cores. (3) At least one of the plurality of stators is configured such that the phase shift of the voltage applied between the plurality of stators can be set to an arbitrary phase shift within the range of 0° to 180°. 3. The variable speed induction motor according to claim 1, wherein said voltage phase shifting device includes a stator rotatably formed concentrically with said rotor.