JP2002136184A - Operation controller for induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a constant output operation, which does not require enlargement of motor structure and inverter and which does not produce torque shocks. SOLUTION: A coil of an induction motor 1 is formed in the structure of the two sets of the independent identical winding in the single-layer concentric winding and double-layer overlap winding provided with six lead terminals for three phases. Conversion for number of poles of 1:2 can be executed for the induction motor 1 through the operation in which two inverters 2, 3 are controlled with the inverter controller 4, so that the same output phase is attained in the low speed range of the constant output range and through the operation in which two inverters are controlled, so that the phases are inverted by 180 degrees in the high-speed range. Consequently, the maximum torque characteristic of the induction motor is set high in the high-speed range and shortage of torque in the high speed range can be eliminated, without having to enlarge the structure of the induction motor. Moreover, both inverters are set to provide the equal output capacity which can be obtained by dividing the structure of the existing inverters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control device for an induction motor having windings for operating the induction motor at a variable speed in a wide range from a constant torque range to a constant output range.

[0002]

2. Description of the Related Art Frequency control using an inverter as a power source is often used for variable speed control of an induction motor. At this time, a torque characteristic is a constant torque characteristic, and a supply voltage is increased in proportion to an increase in speed. As shown by the solid line in FIG. 6, the rotational speed-torque characteristic in this frequency control is 1 / inversely proportional to the increase in the frequency f due to the restriction of the voltage V of the power supply in the constant output range exceeding the constant torque range. The torque T decreases at the curve f. Also, in the figure, the broken line is the maximum torque characteristic T 'of the induction motor, and at a rotation speed higher than the frequency af at the intersection with the torque characteristic T, the output torque is limited by the maximum torque characteristic T'. . a is generally an arbitrary number greater than 2, but is satisfied if it is 1 or more.

When operating an induction motor in a constant output range,
The torque decreases as the speed becomes higher, and the torque is limited by the maximum torque characteristic of the induction motor. Depending on the load, the torque may be insufficient. The following three methods are known as conventional driving methods for solving this torque shortage.

(1) To make the induction motor large in size. By using an induction motor having a large maximum torque characteristic T ', the rotational speed 2af is obtained by the maximum torque characteristic T "instead of the maximum torque characteristic T' as shown in FIG.
Up to the torque characteristic T can be obtained.

(2) To make the inverter large in size
You. By increasing the output capacity of the inverter,
As shown, the output voltage is V ₁To V_TwoChange to induction motor
T to the maximum torque characteristics of the machine₁’To T₁To get the number of rotations 2
Guarantee torque up to af.

(3) The connection of the windings of the motor is switched.
When the operation speed exceeds a certain range, the connection between the winding switching terminal of the induction motor and the inverter is switched to perform the operation in which the pole number is converted.

[0007]

In the conventional driving method, in the method of increasing the size of the induction motor, in order to obtain a torque-up value of 2af / af = 2 times, the size of the motor is also twice as high. This leads to an increase in the size of the device.

In the method of increasing the physical size of the inverter,
When the torque increases, the output current of the inverter also increases due to the change in the voltage characteristics, and the inverter itself becomes larger.

The method of switching the connection of the electric motor requires a changeover switch, and there is a problem that a continuous variable speed operation has a switching operation period corresponding to an idle time of the operation, resulting in a torque shock at the time of switching. In addition, the open / close life and failure of the switch become problems.

An object of the present invention is to provide an operation control device for an induction motor that obtains a constant output operation without increasing the size of the motor and the inverter and without causing a torque shock.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises an induction motor having a stator winding having three phases and six lead terminals, and three terminals of the induction motor. A pair of inverters that supply three-phase currents of which frequency is controlled to the two sets, and control that the outputs of the two inverters are in the same phase in a constant output range of the induction motor and a low-speed operation range equal to or lower than a predetermined rotation speed. In the high-speed operation range exceeding the predetermined rotation speed, the output phase of one inverter is set to 18
An inverter control device capable of inverting by 0 degrees, making the output frequency of both inverters approximately half that of the control in the low-speed reverse rotation range, and performing control with the phase rotation inverted. Features.

Further, the inverter control device according to the present invention operates the voltage control signals or the current control signals u ₁ , v ₁ , w ₁ , u ₂ , v ₂ , w ₂ of the two inverters according to one of the following equations. The phase and frequency of the inverter are switched between the low-speed operation range and the high-speed operation range.

[0013]

(Equation 5)

[0014]

(Equation 6)

Further, the present invention relates to a six-phase winding having an equivalent six-phase winding.
An induction motor having a stator winding having two extraction terminals, an inverter for supplying a six-phase current whose frequency is controlled to the six extraction terminals of the induction motor, and a predetermined output within a constant output range of the induction motor. In the low-speed operation range below the rotation speed, the phase of each phase output of the inverter is sequentially shifted by 2π /
In the high-speed operation range exceeding the predetermined rotation speed, the phase of each phase output of the inverter is sequentially shifted by π / 3, and the frequency is controlled by approximately 1 when the control is performed at the low speed. / 2, and an inverter control device that performs control at a high speed.

Further, the inverter control device according to the present invention comprises:
A voltage control signal or a current control signal u _{1 of} the inverter,
v ₁ , w ₁ , u ₂ , v ₂ , w ₂ are operated according to any of the following equations, and the phase and frequency of the inverter are switched between a low-speed operation range and a high-speed operation range.

[0017]

(Equation 7)

[0018]

(Equation 8)

[0019]

When two three-phase inverters are used, the current supplied to the stator winding of the induction motor is changed by 18 degrees in phase inversion.
By changing it by 0 degree, and when using one 6-phase inverter, by adjusting the phase of the supply current,
A one-to-two pole number conversion is obtained in the winding configuration, the maximum torque characteristic of the induction motor is increased in a high-speed region, and torque shortage in a high-speed region is eliminated without increasing the size of the induction motor.

Further, according to the present invention, the control signal of the inverter is provided with an amplitude correction function K ₁ (t), K ₂ (t) and 1
/ 2 frequency signal, and the operating range is changed by changing the value of one amplitude correction function from 1 to 0 and changing the value of the other amplitude correction function to 0 according to the passage of time t within the switching time T. Smooth signal switching is performed by the peak value control by changing the signal from "1" to "1". In addition, the windings have two independent sets of single-layer concentric winding and two-layer lap winding, and have an equivalent six-phase winding, which is convenient for pole number conversion.

[0021]

FIG. 1 is a block diagram showing an embodiment of the present invention. The induction motor 1 is configured such that its stator winding has three phases and has six lead terminals U ₁ , V ₁ , W ₁ , U ₂ , V ₂ , and W ₂ , and two three-phase inverters 2 and 3 Driven by The common variable speed inverter control device 4 for the inverters 2 and 3 uses an automatic speed control system or an open loop speed control system which performs speed control calculation based on a speed command and a detected value of the number of revolutions to output the output frequencies of both inverters 2 and 3. Control the voltage.

The output capacity of the inverters 2 and 3 is
The number of inverters is equivalent to the controllable current capacity obtained by dividing the number of inverters into two. That is, the main circuit switching elements of the inverters 2 and 3 have a configuration using a small-sized one whose controllable current is half, or a configuration in which the number of parallel elements is reduced by half in a main circuit having a parallel configuration of the switching elements.

When operating the induction motor 1 at a rotation speed up to the frequency af within the constant torque range and the constant output range, the inverter control device 4 performs control in which the output voltage phases of the two inverters 2 and 3 are in phase. When the induction motor 1 is operated in a high-speed range exceeding the frequency af, the voltage phase of one inverter 3 is inverted by 180 degrees, and the output frequency of both inverters 2 and 3 is halved to reverse the phase rotation. The relationship between the switching phases at this time is shown in Table 1 below.

[0024]

[Table 1]

With this control, a one-to-two pole conversion can be equivalently performed on the induction motor 1. That is, in the low-speed region where the inverters 2 and 3 are operated in the same phase, four poles of N, S, N and S are formed from the current directions (indicated by arrows) in the two windings 1 ₁ and 1 _2. 1 ₂
Is inverted as shown by the broken line, and the number of poles is converted into N and S poles.

At the time of conversion from four poles to two poles, by reducing the frequency to １ ／, the number of rotations becomes the same before and after the number of poles is switched. enter. Further, in the high speed range by the number conversion electrode, as shown in FIG. 2, the induction motor maximum torque characteristic T 'is doubled in frequency af of, at frequencies up 2af by drop from the torque 1 / f ² characteristic Operating torque can be obtained.

FIG. 3 shows an equivalent circuit of an induction motor with four poles and two poles. In conversion into two poles, primary and secondary reactances x ₁ and x ₂ are reduced to _１ ／, and a mutual reactance x _n Becomes 77%. In these equivalent circuits, the maximum torque T
m is represented by the following equation.

[0028]

(Equation 9)

In this equation, since x ₁ and x ₂ are sufficiently larger than the primary resistance r ₁ in the high-speed range, the maximum torque Tm can be expressed by the following equation. become.

[0030]

(Equation 10)

FIG. 4 shows a configuration diagram of the inverter and the control device according to the present invention. Both inverters 2 and 3 are configured as a voltage-type or current-type three-phase transistor inverter main circuit. Inverter control device 4 generates a gate signal for each phase transistor of inverters 2 and 3.

Here, generation of the gate signal of the inverter control device 4 is controlled according to the following equation.

[0033]

[Equation 11]

Here, the amplitude correction function K ₁ (t), K
₂ (t) is the time t when the operation range of the induction motor 1 is switched.
Is adjusted in the range of 1 and 0 according to the progress of. As a result, a gate control signal in which the amplitude correction function K ₁ (t) of the first term of the above equation is 1 and the amplitude correction function K ₂ (t) of the second term is 0 is generated in the low speed operation range. Correction function K
₁ (t) and K ₂ (t) are for minimizing a transient phenomenon when the phase and frequency of the inverters 2 and 3 are switched, and may be another function described later.

Thereafter, when switching to the high-speed operation range, the function K ₁ (t) is adjusted from 1 to zero and the function K ₂ (t) is adjusted from 0 to 1 during the time T. By this adjustment, the component of the first term in each of the above equations gradually decreases, and the component of the second term gradually increases. After the time T, only the component of the second term remains.

Conversely, when switching from the high-speed operation range to the low-speed operation range, the function K ₁ (t) increases from zero to 1 and the function K ₂ (t) decreases from 1 to zero. Transfer to the components of the term.

When the operating range is switched, the first and second terms of the above equation have different angular velocities, so that mutual interference is avoided, and the torque generated in the induction motor 1 is the same as that generated by the first term. It is the sum of what occurs in the two terms. Since the torque generated by the induction motor 1 is proportional to the square of the voltage, the sum of the torque generated by the first term and the torque generated by the second term is always constant during switching. In other words, even at the time of switching, the generated torque of the induction motor 1 does not fluctuate, and switching without torque shock can be performed.

Therefore, the control signal generator of the inverter controller 4 has the function generator of the above formula to generate the gate signal, and only the amplitude correction function is controlled for switching the operation range. The configuration is sufficient, and the operation range can be switched smoothly.

It should be noted that the type of the two inverters 2 and 3 in FIG. 4 is not limited to the voltage type, and the same effect can be obtained by using a current type.

The generation of the gate signal of the inverter control device 4 may be controlled according to the following equation.

[0041]

(Equation 12)

In the above equation 12, T ₁ and T ₂ are represented by:
Since the value is not less than the secondary time constant of the motor at the time of low-speed operation and at the time of high-speed operation, it is possible to minimize the transient phenomenon when the phase and frequency of the inverters 2 and 3 are switched.

FIG. 5 shows another embodiment of the present invention. Induction
The motive 11 includes a six-phase wound stator winding.
Six lead terminals U drawn from the phase winding₁,
V₁, W ₁, U_Two, V_Two, W_Twohave. This induction
The motor 11 is operated by one six-phase inverter 12.
The output frequency and voltage of the inverter 12 are
It is controlled by the control device 14.

When operating the induction motor 11 in the constant torque range and the constant output range and at the rotation speed up to the frequency af, the inverter control device 14 controls each phase U of the inverter 12.
_{1, V 2, W 1,} U 2, V 1, W 2 of the _second phase in this order
When the induction motor is operated in a high speed range exceeding the frequency af by shifting by π / 3, the phases U ₁ ,
The phases of V ₂ , W ₁ , U ₂ , V ₁ , and W ₂ are π / 3 in this order.
The frequency is halved at the same time. With this control, one-to-two pole number conversion can be equivalently performed on the induction motor 11.

The generation of the gate signal of the inverter control device 14 may use any of the following two.

[0046]

(Equation 13)

[0047]

[Equation 14]

Here, the amplitude correction function K ₁ (t), K
₂ (t) is adjusted to a range between 1 and 0 as time t elapses when the operation range of the induction motor 11 is switched. As a result, a gate control signal in which the amplitude correction function K ₁ (t) of the first term of the above equation is 1 and the amplitude correction function K ₂ (t) of the second term is 0 is generated in the low speed operation range.

Thereafter, when switching to the high-speed operation range, the function K ₁ (t) is adjusted from 1 to zero and the function K ₂ (t) is adjusted from 0 to 1 during the time T. By this adjustment, the component of the first term in each of the above equations gradually decreases, and the component of the second term gradually increases. After the time T, only the component of the second term remains.

Conversely, when switching from the high-speed operation range to the low-speed operation range, the function K ₁ (t) is increased from zero to 1 and the function K ₂ (t) is adjusted to decrease from 1 to zero. Transfer to the components of the term.

When the operating range is switched, the first and second terms in the above equation have different angular velocities, so that they do not interfere with each other, and the torque generated in the induction motor 1 is the same as that generated by the first term. It is the sum of what occurs in the two terms. Since the torque generated by the induction motor 11 is proportional to the square of the voltage, the sum of the torque generated by the first term and the torque generated by the second term is always constant during switching. That is, even at the time of switching, there is no change in the torque generated by the induction motor 11, and switching can be performed without torque shock.

Therefore, the control signal generator of the inverter controller 14 has the function generator of the above formula to generate the gate signal, and only the amplitude correction function is controlled for switching the operation range. The configuration is sufficient, and the operation range can be switched smoothly.

The type of the inverter 12 shown in FIG. 5 is not limited to the voltage type, and a current type can be used to obtain the same operation and effect.

The above-described inverter control devices 4 and 14
In the above, the number of rotations for switching from low-speed operation to high-speed operation during acceleration and the number of rotations for switching from high-speed operation to low-speed operation during deceleration were the same af, but the number of rotations for switching from low-speed to high-speed and the number of rotations for switching from high-speed to low-speed were set. It may be shifted to have hysteresis. If the number of rotations to be switched is one, hunting may occur and the operation may become unstable if operated near this number of rotations, but stable operation can be achieved by providing hysteresis.

Next, a winding for the above-described operation control will be described. As described so far, the motor terminal of the winding is 3
Six terminals are required regardless of the phase or the six-phase, and six windings are required corresponding to this number. That is, as shown in FIG. 9, the arrangement of the six windings is set to be u ₁ , v ₁ , w ₁ , u ₂ , v ₂ , w ₂ phases in order along the rotation direction of the rotor,
The low-speed operation range of the constant power operation, u ₁ as shown in FIG. 9 (a), v _1, the windings of w ₁ phase connected to the first inverter 2 terminal uvw, similarly u _2, v ₂ , w _Two- phase windings are connected to the second inverter 3. In this case, each winding u
₁ , v ₁ , w ₁ , u ₂ , v ₂ , w ₂ are single-layer concentric windings or double-layer lap windings, and the first set of u ₁ , v ₁ , w ₁ phases and u ₂ ,
The second set of the v ₂ and w ₂ phases is the same connection of Δ or Y respectively.

On the other hand, in the high speed operation range in the constant output operation,
As shown in FIG. 9B, the windings of the phases u ₁ , v ₁ , w ₁ are connected to the terminal uvw of the first inverter 2, and u ₂ , v ₂ ,
The _two- phase winding is connected to -uvw of the second inverter 3. As described above, the conversion between the phase sequence and the phase of the inverter changes the low-speed operation range to the high-speed operation range from four poles to two poles. In this way, two sets of three-phase windings are independently arranged, which is equivalent to a six-phase winding, and the voltage or current signal applied to each set is changed according to the above formula as 1/2 frequency. For example, pole number conversion without torque shock is possible.

FIGS. 10 and 11 show examples of single-layer concentric windings, in which the number of poles is converted into 2/4/4 with 36 stator slots. In FIG. 10, u ₁ ,
The first set of the v ₁ and w ₁ phases and the second set of the u ₂ , v ₂ and w ₂ phases are Y-connections each having a neutral point O ₁ O ₂ .
In the above, the first set and the second set are each set to a Δ connection.

FIG. 12 shows an example of a double-layer lap winding.
An example of connection is shown. Also in this example, the number of fixed slots is 36.
The number of turns is two times that of FIG.
The conversion of the number of poles of eight poles is performed. In this case, when the winding is viewed as a winding in a high-speed operation range because the winding is divided into two phases,
The windings of each homologous pole are connected in series to form one phase, and windings having a phase of 2π / 3 at an electrical angle in a high-speed operation range are collected.
A set of three-phase windings. FIG. 13 shows an example of two-layer lap winding, in which the number of poles is converted from two to four.
Here, a YY connection in which the number of slots is 12 and the electrical angle is π / 3 is shown.

The above is an example of single-layer concentric winding and double-layer lap winding.
However, various types of windings are conceivable.
The conditions are as follows. (1) The winding pitch of each winding is the magnetic pole pitch in the high-speed operation range.
About 1/2. In this case, the magnetic
Although it is all the windings for the pole pitch, an image pole
Can be (2) Two-phase / 4-pole or more motors have two 1-phase windings
That is all. In this case, considering the electrical angle in the high-speed operation range
Windings with the same phase can be connected in series or in parallel.
1 phase. (3) Each phase is 2π / each other when viewed from the electrical angle in the high-speed operation range.
The three phases at position 3 are the first set and the remaining three phases are the second set.
The first set and the second set are both Y-connection or Δ-connection. (4) Regarding the phase order, the first set is u₁, V₁, W₁Made
When it is located at the position of π from the electrical angle of the high-speed operation range,
U sets of windings_TwoAnd the rest in the same direction v as the first set _Two, W_Two
And

[0060]

As described above, according to the present invention, the winding configuration of two independent sets of identically connected induction motors of single-layer concentric winding and double-layer winding is configured to have six lead terminals in three phases. Or a system configuration in which a six-phase winding has six terminals, and a one-to-two pole conversion is provided to the induction motor by the presence or absence of phase inversion between the two inverters and the phase adjustment of the six-phase inverter. Therefore, the operation in the constant output range without running out of torque can be performed without increasing the size of the induction motor and without increasing the size of the inverter. Further, since the number of poles is switched by the output control of the inverter as compared with the conventional winding switching method, the problems of idle time generation and failure due to the conventional changeover switch are eliminated.

According to the present invention, the control signals of the two inverters are signals having amplitude correction functions K ₁ (t) and K ₂ (t) and including a signal of 周波 数 frequency, so that the operation range can be switched. Changes the value of one amplitude correction function from 1 to 0 and changes the value of the other amplitude correction function from 0 to 1 within the switching time T according to the elapse of time t. Switching can be performed.

By providing hysteresis in the switching speed between low-speed operation and high-speed operation, stable operation can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a characteristic diagram of the embodiment.

FIG. 3 is an equivalent circuit diagram of pole number conversion according to the embodiment.

FIG. 4 is a configuration diagram of an inverter and a control device according to the embodiment.

FIG. 5 is a configuration diagram showing another embodiment of the present invention.

FIG. 6 is a graph showing the relationship between the rotational speed and the torque of the induction motor.

FIG. 7 is a characteristic diagram showing a modified example of a conventional maximum torque characteristic.

FIG. 8 is a characteristic diagram showing a conventional example of changing the inverter capacity.

FIG. 9 is a principle diagram of a winding example.

FIG. 10 is a single-layer concentric winding (YY) connection diagram.

FIG. 11: Single-layer concentric winding. Δ-Δ) Connection diagram.

FIG. 12 is a two-layer lap winding (YY) connection diagram.

FIG. 13 is a two-layer lap winding (YY) connection diagram.

[Description of Signs] 1,11 Induction motor 2,3,12 Inverter 4,14 Inverter control device

Claims (7)

[Claims] 1. An induction motor having a stator winding having three extraction terminals with three phases, and a pair for supplying a frequency-controlled three-phase current to two sets composed of three terminals of the induction motor. And in the constant output range of the induction motor and in a low-speed operation range of not more than a predetermined rotation speed, control is performed so that the outputs of the two inverters are in phase, and in the high-speed operation range exceeding the predetermined rotation speed, one of the inverters is controlled. Output phase of 1
An inverter control device capable of inverting by 80 degrees, making the output frequency of both inverters approximately half that of the control in the low-speed operation range, and performing control with the phase rotation inverted. An operation control device for an induction motor. 2. The inverter control device according to claim 1, wherein the inverter control device calculates a voltage control signal or a current control signal u ₁ , v ₁ , w ₁ , u ₂ , v ₂ , w ₂ of the two inverters as follows: An operation control device for an induction motor, which operates according to the following, and switches the phases and frequencies of both inverters to switch between a low speed operation range and a high speed operation range. 3. The inverter control device according to claim 1, wherein the inverter control device converts a voltage control signal or a current control signal u ₁ , v ₁ , w ₁ , u ₂ , v ₂ , w ₂ of the two inverters into the following equation: An operation control device for an induction motor, which operates according to the following, and switches the phases and frequencies of both inverters to switch between a low speed operation range and a high speed operation range. 4. An induction motor having a stator winding having six lead terminals equivalently wound in six phases, and supplying a frequency-controlled six-phase current to the six lead terminals of the induction motor. And an inverter that performs low-speed control in which the phase of each phase output of the inverter is sequentially shifted by 2π / 3 in a low-speed operation range that is within a constant output range of the induction motor and equal to or less than a predetermined number of rotations. In the high-speed operation range exceeding the high-speed operation range, the phases of the respective phase outputs of the inverter are sequentially shifted by π / 3, and the frequency is reduced to about 1 / the value obtained when the low-speed control is performed.
2. An operation control device for an induction motor, comprising: an inverter control device that performs control at a high speed of 2. 5. The inverter control device according to claim 4, wherein the voltage control signal or the current control signal u ₁ , v ₁ , w ₁ , u ₂ , v ₂ , w ₂ of the inverter is expressed by the following equation: An operation control device for an induction motor, wherein the operation and the frequency of the inverter are switched between a low speed operation range and a high speed operation range. 6. The inverter control device according to claim 4, wherein the voltage control signal or the current control signal u ₁ , v ₁ , w ₁ , u ₂ , v ₂ , w ₂ of the inverter is expressed by the following equation: An operation control device for an induction motor, wherein the operation and the frequency of the inverter are switched between a low speed operation range and a high speed operation range. 7. The predetermined rotation according to claim 1, wherein the inverter control device switches from low-speed operation to high-speed operation when accelerating. An operation control device for an induction motor, wherein a switching operation is performed by shifting the number of rotations and the predetermined number of rotations for switching from high-speed operation to low-speed operation when decelerating.