JP2009038851A - High-speed motor drive device - Google Patents

Abstract

[PROBLEMS] To generate a high-frequency power supply with a complete sine waveform by a rotary frequency converter, and to operate a permanent magnet type high-speed motor directly connected to a load machine with high efficiency, and to enable stable operation without step-out even when sudden load changes. A low-cost and simple configuration high-speed motor drive device is provided.
An electric motor 3 operated by a commercial power source 1 or an inverter 9, a multipolar high frequency generator 4 mechanically coupled directly to the electric motor, and a load machine driven by a high frequency power source by the high frequency generator. A speed control signal feedback circuit which is composed of a permanent magnet type high speed motor 7 and adjusts the field magnetic flux of the high frequency generator according to the speed signal of the permanent magnet type motor as required in the case of load characteristics that cause load fluctuations. 10 is a high-speed motor drive device to which 10 is added.
[Selection] Figure 8

Description

  The present invention relates to an electric motor drive device that rotates an electric motor at high speed with a high frequency power source.

When driving the electric motor by the commercial power supply, the maximum rotational speed 3000 min ^-1, or 3600 min ^-1 is the limit. However, in load applications, such as screw air compressors, elevator hoisting machines, electric vehicles, etc., an electric motor that rotates at the above rotation speed may be required. In gas turbine generators, ultra-high-speed generators have been developed and put into practical use in the fields of generators directly connected to the turbine shaft of tens of thousands of min ^-1 without mechanical speed reducers, gearless wind turbine generators, and mini hydroelectric generators. It's getting on. This largely depends on the development of digital control technology using a microcomputer and the development and practical application of a permanent magnet type synchronous machine.

  In general, the relationship between the rotational speed of the rotating body and the output is expressed by the following equation as is well known.

P = 1.207 nT × 10 ⁻³
Where P: output [kW], n: number of revolutions [min ⁻¹ ], T: torque required for load [kg-m]
When the load torque is proportional to the square of the number of revolutions like a pump or fan,
P = K ₁ n ³ × 10 ⁻³
However, K ₁ is a constant, and for a load whose required torque is proportional to the rotational speed, such as a motor generator set,
P = K ₂ n ² × 10 ⁻³
However K ₂ is represented by a constant, the output in proportion to the square or cube of the rotational speed is increased. On the other hand, with the same output, a high-speed rotating machine is greatly reduced in size and effective in saving resources.

  For this purpose, the point is how to generate a frequency higher than the commercial frequency. For this reason, motor generators of several thousand kW class that generate electric power of 100/120 Hz using a two-pole motor and a four-pole generator have been put into practical use. However, if the frequency is higher than this, there is a problem in mechanical strength and vibration due to the centrifugal force of the rotating machine, and inductive-synchronous and synchronous-synchronous frequency converters using a rotating machine cannot obtain a frequency power source of 100/120 Hz or higher. difficult.

  On the other hand, it is possible to obtain a static high-frequency power supply by technological advances in semiconductors and their control systems. In the past, prototypes of ultra-high-speed motor drives with tens of thousands of revolutions using inverters and induction motors have been developed. For this reason, the temperature rise and noise were large, and it was not put to practical use. Therefore, it is no longer difficult with a stationary frequency converter using a semiconductor capable of outputting a sine waveform, and a rotary frequency converter is required. Therefore, when an ultra-high speed motor is required, a speed increasing gear is attached and used, but it is not satisfactory in terms of price, maintenance, dimensions, noise, and the like.

  On the other hand, combined with magnetic bearing or air bearing, permanent magnet material with relatively strong magnetic force, metal material that can withstand extremely strong centrifugal force and processing technology, permanent magnet type electric motor has come into practical use. .

  There exists patent document 1 as an example of the prior art which is going to solve this problem by the combination of a frequency converter and a permanent magnet type motor. Next, this conventional example will be described with reference to FIG.

  In FIG. 9, a thyristor motor 21 that is operated by a power source from a load commutated inverter 20, a permanent magnet generator 22 that is mechanically directly connected to the thyristor motor 21, and power generated by the permanent magnet generator 22. The permanent magnet type high-speed motor 7 is driven by the permanent magnet type high-speed motor 7 and is driven by the position detector 23 for measuring the rotational speed of the permanent magnet type high-speed motor 7 and the permanent magnet type high-speed motor 7. A speed detection circuit 24 that detects the rotational speed and outputs a speed feedback signal; a speed control circuit 25 that outputs a current reference signal of the load commutated inverter 20 from the speed feedback signal and a predetermined speed reference signal; The phase comparison circuit 26 that compares the phases of the output power of the magnet generator 22 and the output signal of the position detector 23 is compared with the load comparator. The current control circuit 28 outputs the phase reference signal of the inverter control circuit 27 from the current reference correction signal of the inverter 20 and the current feedback signal from the inverter control circuit 27 that controls the load commutation inverter 20. An electric motor drive device characterized by the above.

  In the above-mentioned Patent Document 1, a permanent magnet generator that cannot adjust the field magnetic flux is used as a power supply device that supplies high-frequency power. Also, with this configuration, a complicated detection circuit and control circuit are necessary so that the control does not become unstable when the load of the permanent magnet type motor fluctuates, and the number of constituent devices is complicated. Further, generally, two expensive permanent magnet type generators and permanent magnet type electric motors are necessary, and there is a problem that the equipment cost is high.

  The present invention has been made in view of the above points, and does not require a complicated control circuit, and realizes a conventional configuration requiring two permanent magnet type rotating machines with one permanent magnet type generator. An object of the present invention is to provide a high-speed electric motor drive device having a possible low-cost and simple configuration.

  In order to achieve the above object, the present invention provides a general-purpose electric motor operated by a commercial power source or an inverter, a claw-pole multipolar high-frequency generator mechanically connected to the general-purpose electric motor, and the claw-pole. A control device that adjusts the field magnetic flux of the multipole high-frequency generator, a permanent magnet high-speed motor that is driven by the power generated by the claw pole multipole high-frequency generator and drives the load machine, and is added depending on the load characteristics. And a device for controlling a field coil current of the permanent magnet generator connected to the rotor position detector of the permanent magnet type high speed motor.

  In the present invention, it is possible to easily obtain a high frequency power supply having a complete sinusoidal waveform from a commercial power supply by using a rotary type frequency converter comprising a general-purpose motor and a high frequency generator. Rotational frequency converters that drive a high-frequency generator with an electric motor have been put into practical use for power and communication since the past. For example, in a frequency converter using an Alexanderson generator, 500 kVA-20,000 Hz. Although there was a device, in the present invention, by adopting an inexpensive and sturdy claw pole high frequency generator instead of a complicated structure like an Alexanderson generator, a high frequency power supply with a complete sine waveform can be easily and relatively It can be obtained at low equipment costs.

Furthermore, the high-speed motor operated by the high-frequency power source is a permanent magnet type motor that is currently in practical use, so that high-speed operation of several tens of thousands of revolutions becomes possible, and even when the load fluctuates, it responds easily with a standard control circuit. In addition, a high-speed electric motor drive device capable of controlling the speed of the electric motor as required can be obtained.
JP-A-5-84000

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a high-speed electric motor drive apparatus according to Embodiment 1 of the present invention, in which electric power is supplied from a commercial power source 1 to an electric motor 3 through an opening / closing device 2. The electric motor 3 can be either an induction motor or a synchronous motor. However, since the synchronous motor is not general and expensive, an induction motor as a general-purpose motor is sufficient. However, in the case of induction motors, the number of rotations decreases from the synchronous speed by the amount of slip, and the output frequency of the high-frequency generator decreases by that amount, but this slight decrease in frequency is within the allowable range on the load machine side. It is advantageous in terms of cost to use an induction motor.

  The electric motor 3 is mechanically directly connected to the claw pole multipolar high frequency generator 4. Here, the structure of the claw-pole multipole type high-frequency generator includes a claw-pole rotor 11, a claw-shaped magnetic pole 12, a field coil 13, and a stator coil 14, as shown in FIG. In this claw-pole type high frequency generator, the field coil 13 is stationary and the rotating part is only the claw-shaped magnetic pole 12, so that it is robust. Further, by adjusting the exciting power of the field coil 13 by the control device 6, it is possible to adjust the value of the generated power of the claw pole multipole type high frequency generator.

The high frequency power generated by the claw pole multipole type high frequency generator 4 is supplied to a permanent magnet type high speed motor 7 directly connected to a load machine 8 via a switch 5. If the commercial power supply is 50 Hz and the motor 3 is a two-pole machine, the rotation speed of the motor 3 is 3000 min ^−1. If the number of poles of the high-frequency generator directly connected thereto is 20, the frequency is 500 Hz and 50 poles. If there is, high frequency electric power having a complete sinusoidal waveform of 1250 Hz is supplied to the permanent magnet type high speed electric motor 7.

  As shown in FIG. 3, the permanent magnet type high-speed motor 7 operated by this high-frequency power source is different from a normal synchronous motor in that a cylindrical rotor 72 is attached to a shaft 71 that rotates at a high speed, and this surface is magnetized. There are a type of magnet 73 and an embedded magnet type in which a permanent magnet 74 is embedded in an armature. Therefore, the armature has a non-convex pole shape and can withstand ultra high speed rotation.

The torque generated by the permanent magnet type high-speed motor 7 is
T = Iφsinθ ……………… (1)
It is represented by However I axis in the stator rotating field, as shown in FIG. 4, a rotating magnetic field which rotates at a synchronous speed n ₀ in the counterclockwise direction. The φ axis is a field axis formed by a permanent magnet rotor and rotates in synchronization with the I axis at a delay angle θ. θ is the phase angle between the I-axis current and the rotor magnetic axis.

  From equation (1), when the permanent magnet type high-speed motor 7 is not loaded, θ = 0, and when the load increases and θ = 90 ° or more, the maximum torque of the motor is exceeded, and the step-out occurs.

The motor k synchronization speed n ₀ is n ₀ = 120 f / P (2)
Where P is the number of poles and f is the power supply frequency. In this case, in the operation without detecting the rotor position (open loop drive), the average speed is constant and only the torque increases even when the current I, and hence the voltage V, is increased from the equation (1). The rotational speed changes only by changing f. The speed-torque characteristics of this part are as shown in FIG.

  In the case of open loop drive, the phase angle θ in equation (1) fluctuates periodically due to load fluctuations. Therefore, even if the average speed is constant, rotation unevenness may occur and the temperature rise may increase. It may not be suitable for efficient operation. However, when there is almost no load fluctuation, the power generation output, that is, the current I is adjusted by the field magnetic flux control device 6 of the claw pole high frequency generator 4 for the slight load fluctuation in the configuration shown in FIG. The permanent magnet motor 7 can be operated by torque control.

  Therefore, for high-speed driving of a load that does not require strict control and has a small load fluctuation, the high-speed motor driving that is the lowest cost and has been difficult to realize in the past with the simple configuration in FIG. A device can be provided.

(Embodiment 2)
The first embodiment is suitable when the load variation is relatively stable, but may be undesirably out of step when the load variation changes greatly. Therefore, in the second embodiment, a rotor position detection circuit is provided in the permanent magnet type high-speed motor 7 so that the operation can be continued even if the load changes suddenly. The second embodiment will be described with reference to FIG. 6 in which the same parts as those in FIGS.

  In the second embodiment, the rotor position of the permanent magnet type high-speed motor 7 is detected by a hall element or the like as in the known example shown in FIG. 9, and the hall element is arranged at a position where θ = 90 ° in the equation (1). By operating by controlling the field coil current of the permanent magnet type high speed generator with the output of the Hall element, the generated torque of the motor is always maximized and high efficiency operation is performed.

By providing the position detector 23, the phase of the current and magnetic flux is fixed in the speed-torque characteristics. Therefore, the voltage applied to the permanent magnet type high-speed motor 7 is V, the resistance of the stator coil is R, and the induced voltage is If E, the inflow current is I, and the rotational speed of the rotor is N,
V = RI + E
E = K ₁ N
T = K ₂ I
T = K ₂ (V−K ₁ N) / R (3)
However, K ₁ and K ₂ are proportional constants.

FIG. 7 shows the speed-torque characteristics with the expression (3) representing the speed N on the vertical axis and the torque T on the horizontal axis and the applied voltage V as a parameter. That is the load torque at the time is 7 detects the speed to drive in a constant speed when the T _1, it may be adjusted the applied voltage V to be constant. Specifically, the field magnetic flux control device 6 of the claw pole type multipole high frequency generator may be adjusted to a required voltage by a speed signal.

If the load suddenly increases and reaches the torque T ₂ in FIG. 7, the rotational speed N ₁ decreases to N ₂ . In order to return this speed to the original speed N ₁ , the applied voltage is set to V _{2. If} the field flux of the claw pole multipole type high frequency generator 4 is increased by the controller 6, the generated voltage is increased. Good. Conversely, when the load decreases and the torque reaches T ₃ , the rotational speed of the load motor increases to N _3, so if the generated voltage is reduced by the control device 6 of the claw pole multipole high frequency generator 4. Good.

  As described above, in the second embodiment, the rotational speed of the permanent magnet type high-speed electric motor 7 is detected by the position detector 23, the speed signal is obtained from the speed detection circuit 24, and the rotational speed becomes constant regardless of the magnitude of the load. In addition, since the generated voltage is controlled as a feedback signal to the field control device of the claw pole multipole type high frequency generator 4, operation is performed with a current corresponding to the load as compared with the first embodiment, so that high efficiency operation is possible. In addition, the problem of step-out does not occur even in the case of a load in which load fluctuation is likely to occur.

(Embodiment 3)
In the case of Embodiments 1 and 2 described above, the motor 3 that drives the claw-pole multipolar high-frequency generator 4 has a constant rotational speed, so that the output frequency of the high-frequency generator is always constant. Therefore, the rotational speed of the permanent magnet type high-speed motor 7 is always a constant speed. However, a variable law may be necessary depending on the load, and the output frequency of the multipolar high-frequency generator 4 must be variable. However, in general, in order to realize a variable speed motor, the load current type inverter 20 and the thyristor motor 21 are configured as shown in FIG. 9 of the conventional example. However, as described above, the control circuit is complicated and expensive. It is difficult to put to practical use.

  Therefore, in the third embodiment of the present invention, a variable frequency of the claw pole multipole type high frequency generator 4 is realized by using a general-purpose inverter that is generally sold and used in various fields. Although the same parts as those in the first and second embodiments are described with reference to FIG. 8, the same parts as those in the first and second embodiments are not described.

  When the load machine 8 requires a variable law as a property of the load, the rotation speed of the drive motor 3 is controlled by the inverter 9. Therefore, the rotation speed of the claw pole multipole type high frequency generator 4 directly connected also changes, and since n changes in the relational expression of f = nP / 120, the output frequency also changes. Therefore, as apparent from the above formula (2), the rotational speed of the permanent magnet type high-speed motor 7 can be adjusted steplessly. As shown in FIG. 5, during the open-loop operation, the rotational speed changes even with the same load. In the case of a load machine with relatively little load fluctuation, the rotational speed of the load machine can be controlled steplessly. In the case of a load with a relatively large load fluctuation, the speed signal of the permanent magnet type high-speed motor 7 described in the second embodiment is fed back, so that stable operation can be performed without stepping out even if a sudden change in the load occurs. It is possible to continue and to easily control the rotation speed of the load.

  Note that the speed control signal feedback circuit 10 that feeds back the speed control signal in FIG. 8 is more cost-effective if it is selected according to the load characteristics.

It is a circuit diagram which shows Embodiment 1 of this invention. It is sectional drawing which shows the structure of the claw pole multipolar type | mold high frequency generator which is a component of this invention. It is a schematic diagram for demonstrating the kind of rotor of the permanent magnet type | mold high-speed electric motor which is a component of this invention. It is a figure for demonstrating the torque generation mechanism of the permanent magnet type | mold high-speed electric motor which is a component of this invention. It is a speed-torque characteristic view of a permanent magnet type high-speed motor for explaining Embodiment 1 of the present invention. It is a circuit diagram which shows Embodiment 2 of this invention. It is a speed-torque characteristic view of a permanent magnet type high-speed electric motor for explaining Embodiment 2 of the present invention. It is a circuit diagram which shows Embodiment 3 of this invention. It is a circuit diagram which shows the conventional high-speed motor drive device.

Explanation of symbols

1. Commercial power
2. Switchgear
3. Electric motor
4. Claw pole multipole type high frequency generator
5. Switchgear
6. Field flux controller
7. Permanent magnet type high speed electric motor
8. Load machine
9. General-purpose inverter
10. Speed control signal feedback circuit
11. Claw pole type rotor
12. Claw-shaped magnetic pole
13. Field coil
14. Stator coil
20. Load commutated inverter
21. Thyristor motor
22. Permanent magnet generator
23. Position detector
24. Speed detection circuit
25. Speed control circuit
26. Phase comparison circuit
27. Inverter control circuit
28. Power control circuit
71. Shaft
72. Cylindrical rotor
73. Surface permanent magnet
74. Embedded permanent magnets

Claims (3)

  An electric motor driven by a commercial power source, a multipolar high-frequency generator mechanically connected to the electric motor, and a permanent magnet type high-speed electric motor driven by a high-frequency power source generated by the high-frequency generator to drive a load machine A high-speed electric motor drive device comprising:   The high-speed motor drive device according to claim 1, wherein the speed signal of the permanent magnet type motor is used as a feedback signal to the field control device of the multi-pole type high frequency generator, so that stable operation can be performed without stepping out even when the load fluctuates. A high-speed electric motor drive device that makes it possible.   3. The high-speed motor driving device according to claim 1, wherein the motor for driving the multi-pole type high-frequency generator is operated at a variable speed through an inverter to enable variable speed control of the permanent magnet type motor. A high-speed electric motor drive device characterized by the above.

Images