JPS637157A - Variable speed induction motor - Google Patents

Abstract

PURPOSE:To reduce the slip loss of a variable speed induction motor by effectively operating a revolving magnetic flux induced from a main winding and a rectangular magnetic flux from an exciting winding to generate a large torque. CONSTITUTION:A stator 2 is disposed concentrically outside a pivotally mounted rotor 4. The stator 2 is furnished with a main winding 20 and an exciting winding 21. The winding 20 is coupled through a voltage regulator 22 with a power source, and the winding 21 is connected through a rectangular AC current generator 23 having a phase shifter with the power source. When the winding 20 is energized by the power source through the regulator 22, the rotor 4 rotates. The inductance of a rotor conductor 5 can be reduced by controlling the phase of the rectangular magnetic flux by the phase shifter built in the generator 23.

Description

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

Prior art and its problems One method of controlling the speed of the 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 computers and their credit card type electrical control equipment or overheating of capacitors. Among these, measures against harmonic interference can be taken by installing filters. 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 region.

In wire-wound motors, the method of controlling the speed by changing the secondary resistance and changing the slip allows continuous speed control with relative ease. Inserting a resistor into the circuit requires maintenance and inspection due to brush wear, and the squirrel cage induction rock has the problem that speed control cannot be performed by changing the secondary resistance.

OBJECTS OF THE INVENTION The present invention improves the drawbacks of the above-mentioned prior art, allows the speed control range to be set in a wide range and steplessly to any desired speed, and can be started with any torque. Another object of the present invention is to provide a variable speed induction motor that generates powerful torque with high efficiency over the entire speed range from the starting point to the maximum rotational speed.

The variable speed induction motor of the present invention can be formed into either a single-phase or three-phase type, and the rotor can be of a normal squirrel cage type, a double squirrel cage type, a deep groove cage type, a special squirrel cage type with 9 windings, etc. It can be applied to any type of conductor, and the conductor used in the explanation of the present invention refers to a conductor installed in a squirrel cage rotor core,
and each of the windings wound around the wound rotor core.

Furthermore, it is a theory that the square waves used in the description of the present invention are not necessarily at right angles, but include those with partially curved lines or oblique lines; however, in principle, the square waves of the present invention include It has horizontal straight parts on the top and bottom sides.

Means for Solving the Problems In order to achieve the above-mentioned technical problems, the present invention provides a rotor that is rotatably mounted on a shaft, and a stator is disposed concentrically outside the rotor, and a main winding is attached to the stator. a wire and an excitation winding, the main winding being coupled to a power source via a voltage regulator, and the excitation winding being coupled to a power source via a square wave alternating current generator with a phase shifting device. This was done as a means to solve the problem.

Operation With the above configuration, when the main winding is energized from the power source via the voltage regulator, an induced voltage flows through the rotor conductor due to the magnetic flux of the rotating magnetic field generated in the stator, causing the rotor to rotate. By increasing or decreasing the voltage input from the power supply to the main winding using a voltage regulator, the voltage induced in the rotor conductors changes, and the rotation speed of the rotor changes according to the change in the voltage induced in the rotor. do.

By the way, since the excitation winding is wound around the stator, the square wave magnetic flux, which is static magnetic flux that changes instantaneously for each arbitrary electrical angle, is transmitted through the excitation winding by the current flowing from the square wave alternating current generator. By controlling the phase of the square wave magnetic flux produced in the stator and provided in the square wave alternating current generator by means of a phase shifter, the inductance of the rotor conductors becomes very small;
Larger torque can be produced by both the rotating magnetic flux induced by the main winding and the square wave magnetic flux from the excitation winding.
It becomes an electric type with low slip loss and high efficiency.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 6.

The variable speed induction motor number, generally indicated by the reference numeral 1 in FIGS. 1 and 2, is constructed as follows. The stator 2 is fitted and fixed in the machine frame 3, and a plurality of conductors 5 are attached to the rotor core 4.
The short-circuit rings 6 and 7 are connected to both ends of the rotor 8, which is equipped with the rotor 8 and the impeller 9, 10.
is attached to the rotor shaft 11, the rotor 8 is inserted into the inner circumferential surface of the stator 2, and the bearing 1 is fixed to both sides of the machine frame 3.
The rotor shaft 11 is attached to the bearing fi12.13 fitted with 4.14.
The rotor 8 is rotatable by being mounted on a shaft. The rotor core 4 is provided with a plurality of ventilation holes 15 that pass through both sides thereof, and the rotor core 4 is provided with ventilation holes that communicate with the outer circumference of the rotor 8 and the ventilation holes 15. A plurality of ventilation shells 17... and exhaust holes 1 are provided in the stator 2 and the machine frame 3.
8... are opened, and a plurality of ventilation holes 19... are provided in the bearing plate 12, 13.

Next, the windings wound around the stator 2 will be explained with reference to FIG.

The stator 2 is wound with a main winding 20 and an excitation winding 21 which are connected in a delta manner. 21 is a square wave alternating current using, for example, a frequency-invariant thyristor equipped with a phase shift device such as a phase shift device using a connection changeover switch, a phase shift device formed by a single-phase transformer and a connection changeover switch, or an induced voltage adjustment device. It is connected to the power supply via a generator 23.

The operation of the above configuration will be explained below.

By energizing the main winding 20 wound around the stator 2 from a power source via the voltage regulator 22, a magnetic flux of a rotating magnetic field is generated in the stator 2. Furthermore, when a square wave current flows from the power source to the excitation winding 21 via the square wave alternating current generator 23,
A square wave magnetic flux is generated in the stator 2, and the rotor 8 is rotated by causing a composite magnetic flux of the rotating magnetic flux and the square wave magnetic flux to flow through the conductors 5 of the rotor 8.

Next, to explain the speed change control of the rotor 8, the main winding 20 is controlled by operating the slider of the voltage regulator 22, for example.
The rotational speed of the rotor 8 is changed by controlling the voltage flowing to the conductor 5 of the rotor 8 by increasing or decreasing the voltage input to the conductor 5 of the rotor 8. rotation speed. Therefore, when controlling the rotation speed to medium speed or low speed, the voltage regulator @22 is used to control the main winding 2.
The voltage value input to 0 will be reduced, but in this case, efficiency and torque will decrease.

'However, since the excitation winding 21 is wound around the stator 2, an excitation current is passed through the excitation winding 21 from the square wave alternating current generator 23, and the excitation winding 21 is set at an arbitrary electrical angle (for example, 60°). , however, it is not limited to 60'; in the following, only 60° will be described for ease of explanation). A composite magnetic flux of the rotating magnetic flux generated by the winding 20 and the square wave magnetic flux is applied to the current flowing through the conductors 5 of the rotor 8 to generate a larger torque.

Furthermore, to explain the action of the square wave magnetic flux in detail, when a square wave alternating current is passed through the excitation winding 21 from the square wave alternating current generator 23 as shown in FIG. 4, a square wave as shown in FIG. Magnetic flux is a stationary magnetic flux that changes instantaneously every 60 degrees in electrical angle. At time T1, a square wave magnetic flux is created in the direction indicated by O degrees in the figure, and at time T2, a square wave magnetic flux is generated in the direction indicated by 60 degrees in the figure. At T1 up to the time when the current is shifted to , the excitation ta current flowing in the square wave alternating current ia, ib, and ic phases becomes static magnetic flux with no change. FIG. 6 shows the state of this stationary magnetic flux, and time T1 indicates when the square wave magnetic flux is 0° among the square wave alternating current flowing through the excitation winding 21.
, the square wave magnetic flux flowing in the ia phase is from time tO to t1
There is only 10 current at , but there is no fluctuation during that time,
In addition, in the ib phase, although it is in the step period, + and - current flow in the same amount, and in the ic phase, there is only - current, but there is no fluctuation during that time, and in the end, the ia phase and the ic phase + and - of the square wave magnetic flux flowing in are canceled out, and ib
Since the square wave magnetic flux of the phase is also canceled out by + and - in its own phase, the same capacity of square wave magnetic flux always flows through the stator 2. From the above, even if the stationary magnetic flux changes its position stepwise every 60° at intervals of ω°C=π/3, the capacity of the square wave magnetic flux does not change.

Therefore, when starting the rotor 8 and in the low speed region, the voltage regulator 22 is operated to apply a low voltage to the main winding 2.
o to reduce the magnetic flux of the rotating magnetic field generated in the stator 2, but the phase of the current induced by the main winding 2o and flowing to the conductor 5 of the rotor 8 is delayed by 90 degrees. Therefore, the phase of the square wave alternating current flowing from the square wave alternating current generator 23 to the excitation winding 21 is advanced by 90° under the control of a phase shifter, and the rotating magnetic flux generated by the main winding 20 and the excitation winding are By increasing the composite magnetic flux with the square wave magnetic flux generated in the winding 21 and causing a large current to flow through the conductors 5 of the rotor 8, it is possible to reduce slip loss and secure a large torque. When the rotational speed of the rotor 8 is changed toward a high-speed rotation region, the voltage input to the winding 20 is increased by the voltage regulator 22 to increase the magnetic flux generated in the stator 2, and the magnetic flux generated in the stator 2 is increased. By adjusting the phase device, the phase of the square wave magnetic flux generated in the excitation winding 21 is made to approach the same phase as the rotating magnetic flux of the main winding 20.

If controlled as described above, the rotating magnetic flux generated in the main winding 2o and the square wave magnetic flux generated in the excitation winding 21 will efficiently act on the current flowing in the conductor 5 of the rotor 8, and each Slip loss can be reduced in the shifting range, and large torque can be produced.

In addition, in order to create a square wave current flowing through the excitation winding 21,
Even if harmonics are generated by the square wave alternating current generator 23, the current flowing through the excitation winding 21 is about 1/10 of the current flowing through the main winding 20, and the square wave alternating current generator 23 The number of switching times for the square wave alternating current created by the inverter is significantly smaller than the number of switching times for creating different frequency current in the inverter, and there is no effect on the commercial power supply, so a filter is installed to ensure safety. Even if measures are taken, the equipment costs will be kept low.

Due to the rotation of the rotor 8, outside air is sucked into the machine frame 3 by the impellers 9, 10 through the ventilation holes 19 formed in the bearing discs 12, 13, and the stator 2... by the impellers 9, 1o. Main winding 2
0. Each of the excitation windings 21 is ventilated and cooled, and the rotor core 4, conductor 5, etc. are cooled by the wind flowing through the ventilation shells 16 through the ventilation holes 15, and the respective Make the function work stably.

Note that there are cases where the rotor core 4 is not provided with the ventilation holes 152 and the ventilation barrel 16, and the voltage regulator is not limited to the above embodiment, but may be a thyristor.

An AC power regulator using a triac or an induced voltage regulator may also be used.

Alternatively, windings may be applied to the rotor core and connected to each other to form an integral rotor, and either star connection or delta connection may be used for the winding and the stator winding. Can be done.

It goes without saying that by electrically connecting a voltage regulator and a square wave alternating current generator equipped with a phase shifter, it is possible to perform automatic control operation that optimizes the rotational speed required of the rotor. It is.

Effects of the Invention As explained above, according to the present invention, the rotating magnetic flux generated by the main winding and the square wave magnetic flux generated by the excitation winding can be efficiently applied to the current flowing through the rotor conductors, thereby reducing slip loss. In addition to improving efficiency by reducing the amount of rotation, the voltage adjustment device uses a voltage regulator and the phase shifter uses a phase shifter to control the phase of the square wave alternating current, making it possible to easily change the speed to any desired rotational speed. Since it is possible to secure torque performance equivalent to that of the load, it is possible to perform smooth startup or startup with arbitrary characteristics according to the startup characteristics of the load, which is a remarkable effect in electric motors that frequently repeat startup, stop, and gear changes.

[Brief explanation of the drawing]

1 to 6 are illustrations of embodiments of the present application. Fig. 1 is a side sectional view of the induction motor, Fig. 2 is a side view showing details of the main parts, Fig. 3 is a connection diagram of the main winding and excitation winding wound around the stator, and Fig. 4 is FIG. 5 is an explanatory diagram of the square wave alternating current, FIG. 5 is an explanatory diagram of the variation angle of the static magnetic flux, and FIG. 6 is an explanatory diagram of the variation of the static magnetic flux. 1... Variable speed induction motor 2... Stator 3... Machine frame 4... Rotor core 5... Conductor
6, 7... Short circuit ring 8... Rotor
9, 10... impeller 11... rotor shaft 1
2.13...Bearing plate 14...Bearing 15
... Ventilation hole 16... Ventilation barrel 17... Ventilation barrel 18... Exhaust hole 19... Ventilation hole 20
...Main winding 21...Excitation winding 22...
voltage regulator

Claims (1)

[Claims] A stator is disposed concentrically outside the rotor, which is rotatably mounted, a main winding and an excitation winding are provided on the stator, and the main winding is connected to a power source via a voltage regulator. Variable speed induction motor, characterized in that the excitation winding is configured to be connected to a power supply via a square wave alternating current generator with a phase shift device.