JPH09271196A - Control equipment of induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent torque insufficiency and surely prevent an induction motor to be locked. SOLUTION: This control equipment converts electric power supplied from a power source PS to specified control power through a power converter circuit 20 and outputs the power to an induction motor CM; controls the power converter circuit 20 in such a manner that the supply frequency and the supply voltage to the induction motor CM change on the basis of previously set reference voltage frequency characteristics; performs the variable speed control of the induction motor CM by controlling the supply frequency to the induction motor CM; adjusts the supply voltage in such a manner that the current of the induction motor CM becomes minimum, by finely changing the supply voltage to the induction motor CM, with a specified changing amount; and sets a limit range in such a manner that the value of a supply voltage to be changed is in a specified range with respect to the reference voltage frequency characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an induction motor, and more particularly to a control device for controlling the current of an induction motor to a minimum.

[0002]

2. Description of the Related Art Conventionally, for example, an induction motor has been used as a compressor in an air conditioner. As a control device for the induction motor, as disclosed in Japanese Patent Publication No. 63-49478, There are motors that maintain high motor efficiency (hereinafter referred to as motor efficiency).

[0003] In this induction motor control apparatus, a power conversion circuit having an inverter circuit converts AC power from a power supply into DC power, and then converts the AC power into controlled AC power and supplies the controlled AC power to the induction motor. The drive frequency of the power control circuit is controlled to output a drive signal to the inverter circuit so as to control the induction motor at a variable speed.

In the power control circuit, reference voltage frequency characteristics are determined in advance based on characteristics of the induction motor, and the supply frequency and the supply voltage are controlled based on the reference voltage frequency characteristics.

The reference voltage frequency characteristic is set in advance so that the motor efficiency is optimized. However, when the load of the induction motor fluctuates due to the fluctuation of the air conditioning load or the like, the optimum voltage value usually fluctuates. Therefore, the motor efficiency may not be the optimum value.

Therefore, after controlling the supply frequency corresponding to the load, the supply voltage is slightly changed to adjust the supply voltage so that the current of the induction motor (hereinafter referred to as motor current) becomes the minimum value. .

[0007]

However, in the above-described induction motor control device, since the range of change of the supply voltage for minimizing the supply current of the induction motor has not been set conventionally, the disturbance due to noise or the like may occur. There was a risk of malfunction and locking of the induction motor. That is,
If the current is erroneously detected as being low even though the supply voltage is reduced and the current of the induction motor is increasing, the supply voltage is further reduced, resulting in insufficient torque for the load. As a result, the induction motor may not operate.

Further, conventionally, the change of the supply voltage for minimizing the supply current of the induction motor is performed by performing the first initial operation from the polarity (minus polarity) where the supply voltage decreases-or the supply voltage. It was not decided whether to execute from increasing + polarity (plus polarity).

In this case, there is a risk that the induction motor will be locked if the first initial operation is performed from the polarity (negative polarity) where the supply voltage decreases. That is, since the supply voltage is lowered, the induction motor may not be driven due to insufficient torque, and smooth start may not be performed in some cases.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent insufficient torque and reliably prevent the induction motor from being locked.

[0011]

[Means for Solving the Problems]

-Summary of the Invention-The present invention converts electric power supplied from a power supply (PS) into predetermined control power via a power conversion circuit (20) and outputs the control power to an induction motor (CM), while an induction motor (CM). ), The power conversion circuit (20) is controlled so that the supply frequency and the supply voltage of the induction motor (CM) change based on a preset reference voltage frequency characteristic, and the induction frequency of the induction motor (CM) is controlled. CM) variable speed control. In addition, the supply voltage of the induction motor (CM) is slightly changed with a predetermined fluctuation amount to adjust the supply voltage so that the current of the induction motor (CM) is minimized, and the voltage value of the supply voltage to be changed is the reference value. The limit range is set so that the voltage frequency characteristic is within a predetermined range.

-Specific Items of the Invention- Specifically, as shown in FIG. 1, the means of the invention according to claim 1 first includes a power supply (PS) and an induction motor (CM). Then, a power conversion circuit (20) that converts the power supplied from the power supply (PS) into predetermined control power and outputs the control power to the induction motor (CM), and outputs a drive signal to the power conversion circuit (20). A drive circuit (31) is provided.
Further, the induction motor (CM) is a control signal for controlling the power conversion circuit (20) so that the supply frequency and the supply voltage of the induction motor (CM) change based on a preset reference voltage frequency characteristic. ), The speed control circuit (41) that outputs a control signal for controlling the induction motor (CM) at a variable speed to the drive circuit (31), and the induction motor (CM).
Optimum control means (42) for outputting to the drive circuit (31) an adjustment signal for adjusting the supply voltage so that the current of the induction motor (CM) is minimized by minutely varying the supply voltage of the motor with a predetermined variation amount. ) And are provided. In addition, limit setting means (43) for setting a limit range in the optimum control means (42) so that the voltage value of the supply voltage changed by the optimum control means (42) is within a predetermined range with respect to the reference voltage frequency characteristic. ) Is provided.

The means taken by the invention of claim 2 is the limit setting means (4) in the invention of claim 1 above.
In place of 3), operation setting means (44) is provided, and the operation setting means (44) increases the supply voltage by the optimum control means (42) at the start of control of the optimum control means (42). The configuration is such that the initial operation of the optimum control means (42) is set so that the increase signal is output to the power conversion circuit (20).

The means taken by the invention according to claim 3 is the same as the invention according to claim 1, further comprising the operation setting means (44) according to the invention according to claim 2.

Further, the means taken by the invention of claim 4 is the induction motor (C
M) is a compressor motor provided in the air conditioner.

-Operation- According to the above-mentioned matters specifying the invention, in the inventions of claims 1, 3 and 4, first, the speed control circuit (41) is
When receiving an air conditioning load signal such as room temperature, it outputs a control signal to the drive circuit (31) based on the reference voltage frequency characteristics,
The drive circuit (31) outputs a drive signal to the power conversion circuit (20) to change the supply frequency of the induction motor (CM).

After that, when the supply frequency stabilizes, the optimum control means (42) executes the optimum control, and adds or subtracts a predetermined variation amount to the current supply voltage to obtain the motor current (current of the induction motor (CM)). Adjust the supply voltage so that

In the above-mentioned optimum control, the limit setting means (43) makes the fluctuation of the supply voltage of the optimum control means (42) within the predetermined limit range M with respect to the reference voltage frequency characteristic L. That is, as shown in FIG. 3, the limit range M is set in a fan-shaped range with the zero voltage point O obtained by extending the reference voltage frequency characteristic L as the origin. The upper limit line Mmax is set corresponding to the maximum load (torque) assumed for the supply frequency, and the lower limit line Mmin corresponds to the minimum torque at which the induction motor (CM) does not lock. Is set.

According to the second and third aspects of the present invention, for example, as shown in the voltage-current characteristic of FIG. 7, when the optimum control is started from the state of V0, the operation setting means (44) first The control operation increases the supply voltage to V1. Since the motor current after this change is lower than the motor current before the change in supply voltage, the supply voltage is increased to V2 also in the next control. Since the motor current after this change is further lower than the motor current before the change of the supply voltage, the supply voltage is also reduced to V3 in the next control.

However, since the motor current after this change is higher than the motor current before the change of the supply voltage, it means that the minimum current point has been exceeded. Therefore, in the next control, conversely, the supply voltage is reduced to. As a result, the motor current after the change is adjusted to the lowest current point.

[0021]

Therefore, according to the first and third aspects of the present invention, since the fluctuation of the supply voltage of the optimum control means (42) is limited within a predetermined limit range, the induction motor (CM). ) Lock can be reliably prevented.
That is, even if disturbance such as noise is mixed, it is possible to reliably prevent the supply voltage from being reduced more than necessary, so that it is possible to always maintain a predetermined torque and prevent a torque shortage with respect to the load. Induction motor (CM)
The lock of can be reliably prevented.

Further, according to the second aspect of the invention, since the initial operation of the optimum control means (42) is started from the + polarity in which the supply voltage increases, the lower limit range of the fluctuation of the supply voltage is limited. It is possible to reliably prevent the induction motor (CM) from being locked due to insufficient torque. As a result, the induction motor (CM) can always be started smoothly, so that the reliability of drive control can be improved.

According to the third aspect of the invention, the fluctuation of the supply voltage of the optimum control means (42) is limited within a predetermined limit range, and at the same time, the initial operation of the optimum control means (42) is changed to the supply voltage. Since a double lock prevention mechanism can be provided because the start is started from + polarity, the drive control reliability can be further improved.

According to the fourth aspect of the invention, it is possible to reliably prevent the motor of the compressor from being locked, so that the reliability of the air conditioning operation can be improved.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 2, (10) is an induction motor (C) of a compressor provided in an outdoor unit of an air conditioner.
M), comprising a power conversion circuit (20) and a power control circuit (30), and supplying control power from a power supply (PS) to the induction motor (CM) via the power conversion circuit (20). doing.

The power conversion section is for converting three-phase AC power supplied from a power source (PS) into controlled three-phase AC power, and includes a rectifying circuit (21), a smoothing circuit (22), and an inverter. And a circuit (23). The rectifier circuit (21) includes six diodes (d1, d1, ...)
A diode module connected to a power source (PS) via a switching circuit (11), which performs full-wave rectification of alternating current from the power source (PS).

The smoothing circuit (22) smoothes the direct current that is full-wave rectified by the rectifying circuit (21), and is provided with a reactor (2L) and a capacitor circuit (2C) having a smoothing capacitor (2C). 2a) and a resistor circuit (2b) having a discharge resistor (2R) are connected to the power supply line (2P, 2
N). The smoothing circuit (22) has a DC section current, that is, an induction motor (C
A current transformer (CT) that is a current detector that detects a motor current that is the current of M) is provided in the power supply line (2N).

The inverter circuit (23) is a transistor including six power transistors (Tr, Tr, ...).
A smoothing circuit (22) is a transistor module that converts a smoothed direct current into an alternating current, and is connected to an induction motor (CM) to supply three-phase AC control power to the induction motor (CM). I have. A free wheeling diode (d2, d2, ...) Is connected between the emitter and collector of the power transistor (Tr, Tr, ...), and the power transistor (Tr, Tr ,. ON / OFF by the drive signal of).

The electric power control circuit (30) is provided with a drive circuit (31) and a CPU (40) while a current signal is input from a current transformer (CT). The drive circuit (31) controls the power transistors (Tr, Tr,...) So that the power transistors (Tr, Tr,...) Perform PWM modulation (pulse width modulation) on the DC section voltage smoothed by the smoothing circuit (22).
The drive signal is output to. An air conditioning load signal such as an indoor temperature is input to the CPU (40).
Speed control means (41) and optimum control means (42) are provided.

An air conditioning load signal such as an indoor temperature is input to the speed control circuit (41), and the supply frequency of the induction motor (CM) which is the operating frequency of the compressor is derived corresponding to the air conditioning load signal. Then, the control signal is output to the drive circuit (31) so as to achieve this supply frequency.

That is, the speed control circuit (41) controls the drive of the inverter circuit (23) so that the supply frequency and the supply voltage of the induction motor (CM) change based on the preset reference voltage frequency characteristic. A control signal for controlling the supply frequency of the induction motor (CM) to control the induction motor (CM) at a variable speed is output to the drive circuit (31). Then, the drive circuit (31) outputs the drive signal to the inverter circuit (23) of the power conversion circuit (20) based on the control signal.

The optimum control means (42) drives an adjustment signal for adjusting the supply voltage of the induction motor (CM) so that the supply voltage of the induction motor (CM) is slightly changed by a predetermined change amount to minimize the motor current. Outputting to the circuit (31). Then, the drive circuit (31) outputs the drive signal to the inverter circuit (23) of the power conversion circuit (20) based on the adjustment signal.

The CPU (40) is provided with a limit setting means (43) and an operation setting means (44) as a feature of the present invention. The limit setting means (43) sets a limit range in the optimum control means (42) so that the voltage value of the supply voltage changed by the optimum control means (42) falls within a predetermined range with respect to the reference voltage frequency characteristic. are doing. Specifically, the limit setting means (43) is ± 15 with respect to the reference voltage frequency characteristic.
The limit range of% is set.

Further, the operation setting means (44), when the control of the optimum control means (42) is started, outputs a + polarity increase signal for increasing the supply voltage by the optimum control means (42) to the drive circuit (31).
The initial operation of the optimum control means (42) is set so as to output to.

-Basic Principle of Control- Therefore, the basic principle of the optimal control executed by the optimal control means (42) will be described.

First, as shown in FIG. 3, the reference voltage frequency characteristic L is set so that the compressor can always be operated with the best compressor efficiency even if the load condition of the air conditioner changes. The supply voltage of the induction motor (CM) (the output voltage of the inverter circuit (23)) is adjusted in accordance with, and the maximum compressor efficiency is set. The horizontal portion of the upper limit of the reference voltage frequency characteristic L in FIG. 3 indicates the rated voltage of the induction motor (CM).

On the other hand, the characteristic of the motor current when the supply voltage of the induction motor (CM) is kept constant and the supply voltage is changed, that is, the voltage-current characteristic is U-shaped as shown in FIGS. There is a minimum current point. In addition, A to E in FIG. 4 and FIG.
15Hz, B 30Hz, C 45Hz, D 60H
z and E are 90 Hz. The subscripts 1 to 4 of A to E indicate the torque kgfm, the subscript 1 is 0.2 kgfm, and the subscript 2 is 0.
4 kgfm, subscript 3 indicates 0.6 kgfm, and subscript 4 indicates 0.8 kgfm. Therefore, for example, A1 indicates a voltage-current characteristic when the supply frequency is 15 Hz and the torque is 0.2 kgfm, and D1 indicates a voltage-current characteristic when the supply frequency is 60 Hz and the torque is 0.2 kgfm. Is shown.

As is apparent from FIGS. 4 and 5, when the torque is changed at the same supply frequency, the minimum current point changes from P1 to P2 in FIG. When a certain load increases, the optimum voltage value also increases.

When the supply frequency is changed while keeping the torque constant, the minimum current point is, for example, P1 to P in FIG.
3, that is, as the supply frequency increases, the optimum voltage value increases, but the motor current is substantially constant.

On the other hand, the characteristics of the motor efficiency η when the supply voltage of the induction motor (CM) is changed and the supply voltage is changed, that is, the voltage motor efficiency characteristics are shown by R1 to R in FIG.
As shown in FIG. 3, the inverted U-shaped quadratic curve is formed, and the supply voltage at the maximum motor efficiency points P4 to P6 substantially matches the supply voltage at the minimum current points P1 to P3 in the voltage-current characteristics. Will be.

From the above voltage-current characteristics and voltage-motor efficiency characteristics, "when the supply frequency and torque (air conditioning load) are determined, the optimum voltage that gives the maximum motor efficiency (minimum current of the induction motor (CM)) is determined at one point. It will be said that.

For the above reason, first, the speed control circuit (4
1) changes the supply frequency output from the inverter circuit (23) based on the reference voltage frequency characteristic L in response to an air conditioning load signal such as indoor temperature. Then, the optimum control means (4
In 2), the supply voltage is adjusted so that the motor current is minimized by slightly changing the supply voltage.

At that time, the operation setting means (44) causes the initial operation of the optimum control means (42) to output a + polarity increase signal for increasing the supply voltage, and the limit setting means (43) further The fluctuation of the supply voltage of the optimum control means (42) is set within the limit range M of ± 15% with respect to the reference voltage frequency characteristic L.

That is, as shown in FIG. 3, the limit range M is set in a fan-shaped range with the zero voltage point O, which is obtained by extending the reference voltage frequency characteristic L, as the origin. The upper limit line Mmax is set corresponding to the maximum load (torque) assumed for the supply frequency, and the lower limit line Mmin corresponds to the minimum torque at which the induction motor (CM) does not lock. Is set.

-Operation of Optimum Voltage Frequency Control- Next, the operation of the optimum voltage frequency control in the induction motor (CM) will be described.

First, as described above, the speed control circuit (4
When 1) receives an air conditioning load signal such as room temperature, it outputs a control signal to the drive circuit (31) based on the reference voltage frequency characteristic L, and the drive circuit (31) outputs the drive signal to the inverter circuit (23). To change the supply frequency of the induction motor (CM).

After that, when the supply frequency is stabilized, the optimum control means (42) executes the optimum control, and as shown in the control flow of FIG. 6, first, in step ST1, the current signal from the current transformer (CT) is supplied. In response, the current motor current I of the induction motor (CM) is stored.

Subsequently, the process proceeds to step ST2, and the optimum control means (42) has a feature of the present invention that the supply voltage V obtained by adding or subtracting a predetermined variation amount ΔV to the current supply voltage V is within the limit range M. It is determined whether or not it is between the upper limit line Mmax and the lower limit line Mmin.

Then, the changed supply voltage V is within the limit range M.
If it is within the range, the determination in step ST2 is YES, and the process proceeds to step ST3. The optimum control means (42) adds or subtracts a predetermined variation amount ΔV to the current supply voltage V, and then proceeds to step ST4. , It is determined whether or not a predetermined control time Δt has elapsed.

Particularly in the initial operation, as a feature of the present invention, the operation setting means (44) outputs an increase signal of + polarity for increasing the supply voltage in the initial operation of the optimum control means (42) to perform the optimum control. The means (42) adds the predetermined variation amount ΔV to the current supply voltage V, and then moves to step ST4.

On the other hand, in step ST2, if the changed supply voltage V is out of the limit range M, the determination becomes NO and the process proceeds to step ST4, in which the optimum control means (42) determines the current supply voltage V. The current state is maintained without changing and the process proceeds to step ST4 to determine whether or not a predetermined control time Δt has elapsed.

Then, the process waits in step ST4 until a predetermined control time Δt elapses, and when this control time Δt elapses, the process proceeds to step ST5 and the motor current In after the change of the supply voltage V is equal to the supply voltage V It is determined whether or not the motor current Im before the change has become less than or equal to.

When the motor current In after the change of the supply voltage V is less than or equal to the motor current Im before the change of the supply voltage V, the motor current I has decreased, and therefore, the process proceeds from step ST5 to step ST6. , The sign of the fluctuation amount ΔV is left as it is, the process returns to the step ST1, and the above-mentioned operation is repeated. That is, for example, when the supply voltage V is decreased and the motor current I is decreased, there is a possibility that the minimum current point still exists. Therefore, the fluctuation amount ΔV is further decreased and the supply voltage V is further decreased. It will be.

On the other hand, in step ST5, when the motor current In after the change of the supply voltage V becomes larger than the motor current Im before the change of the supply voltage V, the motor current I
Therefore, the determination in step ST4 becomes NO, the process proceeds to step ST6, the sign of the variation amount ΔV is inverted, the process returns to step ST1, and the above operation is repeated. That is, for example, when the supply voltage V is decreased and the motor current I is increased, it means that the minimum current point has been exceeded, so the fluctuation amount ΔV is set to a positive sign and the supply voltage V is increased. .

The increase / decrease operation of the supply voltage V is repeated so that the motor current I of the induction motor (CM) is adjusted to be the minimum.

Specifically, as shown in the voltage-current characteristic of FIG. 7, for example, when optimum control is started from the state of V0, first, the operation setting means (44) causes the supply voltage to reach V1 by the first control operation. Increase. In this case, since the motor current In after the change is lower than the motor current Im before the change, the supply voltage is increased to V2 also in the next control. Even in this case, the changed motor current In
However, since it is further lower than the motor current Im before the change, the supply voltage is increased to V3 also in the next control.

In this case, since the motor current In after the change is larger than the motor current Im before the change, it means that the minimum current point is exceeded. So, in the next control,
Conversely, the supply voltage is reduced to V4. As a result, the changed motor current I is adjusted to the lowest current point.

In the above-mentioned optimum control, a feature of the present invention is that the fluctuation of the supply voltage V of the optimum control means (42) is limited to the limit range M shown in FIG.
For example, for a supply frequency of 1, the supply voltage V will vary between Vc1 and Vc2 and will be adjusted to the minimum current point.

-Effects of this Embodiment- As described above, according to this embodiment, the optimum control means (4
Since the fluctuation of the supply voltage in 2) is limited within a predetermined limit range, it is possible to reliably prevent the induction motor (CM) from being locked. That is, even if disturbance such as noise is mixed, it is possible to reliably prevent the supply voltage from being reduced more than necessary, so that it is possible to always maintain a predetermined torque and prevent a torque shortage with respect to the load. It is possible to reliably prevent the induction motor (CM) from locking.

Further, since the initial operation of the optimum control means (42) is started from the + polarity at which the supply voltage increases, the induction motor (CM ) Lock can be reliably prevented. As a result, the induction motor (CM) can always be started smoothly, so that the reliability of drive control can be improved.

Particularly, the fluctuation of the supply voltage of the optimum control means (42) is limited within a predetermined limit range, and at the same time, the initial operation of the optimum control means (42) is started from + polarity at which the supply voltage increases. Therefore, since the double lock prevention mechanism can be provided, the reliability of drive control can be further improved.

Further, the lock of the motor of the compressor in the air conditioner can be reliably prevented, so that the reliability of the air conditioning operation can be improved.

[0064]

Other Embodiments In the present embodiment, the reference operation is set as the initial operation and the limit of the fluctuation of the supply voltage of the optimum control means (42). It is not always necessary to set the initial operation, and it is not always necessary to set the limit range in the invention described in claim 2. In this case, if the initial operation of the optimum control means (42) is started from the positive polarity where the supply voltage increases,
It is possible to reliably prevent the induction motor (CM) from being locked due to insufficient torque without limiting the lower limit of the fluctuation of the supply voltage.

Although the above-mentioned limit range is set to ± 15%, the present invention is not limited to these ranges.

Further, although the present embodiment has been described with respect to the induction motor (CM) of the compressor of the air conditioner, the invention according to claims 1 and 2 can be applied to various induction motors (CM). You can

Further, although the inverter circuit (23) in this embodiment uses six power transistors (Tr, Tr, ...), in the present invention, six IGBTs (Insulated Gate) are used.
Bipolar Transistor) may be used.

[Brief description of drawings]

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

FIG. 2 is a control circuit diagram of the induction motor.

FIG. 3 is a characteristic diagram showing a reference voltage frequency characteristic.

FIG. 4 is a characteristic diagram showing an outline of voltage-current characteristics and voltage motor efficiency characteristics.

FIG. 5 is a characteristic diagram showing specific voltage-current characteristics.

FIG. 6 is a control flow chart of optimum control.

FIG. 7 is a characteristic diagram showing voltage-current characteristics in optimal control.

[Explanation of symbols]

 20 Power conversion circuit 21 Rectifier circuit 22 Smoothing circuit 23 Inverter circuit 30 Power control circuit 31 Drive circuit 40 CPU 41 Speed control means 42 Optimal control means 43 Limit setting means 44 Operation setting means PS Power supply CM Induction motor CT Current transformer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Norio Kagimura 1304 Kanaoka-machi, Sakai-shi, Osaka Daikin Industries, Ltd. Kanaoka factory, Sakai Manufacturing Co., Ltd. (72) Masafumi Hashimoto 1304, Kanaoka-machi, Sakai-shi, Osaka Daikin Industries Ltd. Sakai Factory Kanaoka Factory

Claims (4)

[Claims] An electric power conversion circuit comprising: a power supply (PS) and an induction motor (CM), while converting a power supplied from the power supply (PS) into a predetermined control power and outputting the control power to the induction motor (CM). Two
0), a drive circuit (31) that outputs a drive signal to the power conversion circuit (20), and a supply frequency and a supply voltage of the induction motor (CM) change based on a preset reference voltage frequency characteristic. Control signal for controlling the power conversion circuit (20) so as to control the supply frequency of the induction motor (CM).
The speed control circuit (41) that outputs a control signal for variable speed control to the drive circuit (31) and the induction motor (CM) by slightly varying the supply voltage of the induction motor (CM) with a predetermined variation amount. The optimum control means (42) for outputting an adjustment signal for adjusting the supply voltage to the drive circuit (31) so as to minimize the current, and the voltage value of the supply voltage fluctuated by the optimum control means (42) are the reference values. A control device for an induction motor, comprising: an optimum control means (42); and a limit setting means (43) for setting a limit range so that the voltage frequency characteristic falls within a predetermined range. 2. A power conversion circuit which comprises a power supply (PS) and an induction motor (CM), and which converts electric power supplied from the power supply (PS) into predetermined control power and outputs the control power to the induction motor (CM). 2
0), a drive circuit (31) that outputs a drive signal to the power conversion circuit (20), and a supply frequency and a supply voltage of the induction motor (CM) change based on a preset reference voltage frequency characteristic. Control signal for controlling the power conversion circuit (20) so as to control the supply frequency of the induction motor (CM).
The speed control circuit (41) that outputs a control signal for variable speed control to the drive circuit (31) and the induction motor (CM) by slightly varying the supply voltage of the induction motor (CM) with a predetermined variation amount. The optimum control means (42) for outputting an adjustment signal for adjusting the supply voltage to the drive circuit (31) so as to minimize the current, and the optimum control means (42) at the start of control of the optimum control means (42). ) Has an operation setting means (44) for setting the initial operation of the optimum control means (42) so as to output an increase signal for increasing the supply voltage to the power conversion circuit (20). Electric motor controller. 3. The control device for the induction motor according to claim 1, wherein the optimum control means (4) is activated when the control of the optimum control means (42) is started.
2) the power conversion circuit (2
The control device for an induction motor, comprising: an operation setting means (44) for setting the initial operation of the optimum control means (42) so as to output the optimum control means (42). 4. The control device for an induction motor according to claim 1, wherein the induction motor (CM) is a motor of a compressor provided in the air conditioner.