JP2003204691A - Motor controller, freezer air conditioner, and motor control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure reliability of the operation by improving the accuracy in motor control, even under the condition of a phase current being hardly detected as detecting of the phase current of a motor and driving it by sine waves. <P>SOLUTION: In a motor controller, which is equipped with a voltage inverter equipped with a switching circuit composed of one or more switching elements for adjusting the voltage to be supplied to the motor, a current detector for detecting the current flowing to the motor, and a controller for controlling the switching circuit, based on the detected result of the detector, and controlling the motor, sine wave drive control, where voltage is applied so that the phase current of the motor becomes sine wave form and rectangular wave control, where a voltage of 180° rectangular wave is applied to each phase of the motor are switched over, by the operating state or the conditions of the controller. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device using an inverter, a refrigerating and air-conditioning device using the control device, and a control method.

[0002]

2. Description of the Related Art FIGS. 15 and 16 are block diagrams of a conventional motor control device for generating a sinusoidal drive signal. 15, 1
In FIG. 6, 1 to 6 are drive elements switching elements (Up, Vp, Wp, Un, Vn, W) of three-phase positive and negative, respectively.
n), 11 is a motor, 7 is a DC power supply, 8 is a control unit that outputs drive signals for the switching elements 1 to 6, 9a is a current detection unit that uses one shunt resistor as a current detection element, and 9a.
b is a current detection unit using an ACCT as a current detection element, 1
Reference numeral 2 is a shunt resistor, and 13 is a bus voltage detector. A sine wave drive control in which the current waveform of the motor is a sine wave is performed based on the detection result of each of the current detection units. In addition to the sinusoidal wave drive control, there is an example of a rectangular wave drive drive signal that detects an induced voltage generated in each phase of the motor and applies a rectangular wave voltage of 120 ° to control the motor. For example, when the control device of the synchronous motor is activated, the current is controlled according to the current command value based on the rectangular wave, and after the rotary encoder generates the Z-phase signal indicating the specific position of the rotary shaft, the current command value is based on the sine wave. A technique for controlling current is disclosed in Japanese Patent Laid-Open No. 6-11.
It is known from Japanese Patent No. 3583. This control enables reliable start-up and operation with less torque ripple during normal operation. A technique for switching the drive of the synchronous motor according to the disturbance is known from Japanese Patent Laid-Open No. 2001-245487.

[0003]

In the conventional motor control device, when the ACCT is used for the current detecting portion as in 9b, a phase difference occurs in the detection result at a low rotation speed due to the characteristics of the ACCT, and a high load is applied. When a large current flows due to time, magnetic saturation occurs and it is difficult to accurately detect the current. Further, when DCCT is used instead of ACCT of the current detection unit, accurate current detection is possible, but it becomes extremely expensive and not practical. Further, when a shunt resistor is used in the current detecting portion as in 9a, it is difficult to accurately detect the current under conditions such as when the load of the motor is small or when the DC power supply voltage (bus voltage) is large. Further, a voltage signal including a current signal such as a shunt resistor becomes a pulse signal synchronized with the ON signal of the switching element, and it is necessary to detect the current within the rising time of the pulse. When the load of the motor is small or the DC power supply voltage is large, the pulse rise time becomes short and it becomes difficult to accurately detect the current due to the delay of the circuit such as the current detector.
In order to perform accurate current detection, an expensive microcomputer or DSP (Digital Signal Pro) with a high processing speed is used.
was required to be used. Further, when the induced voltage is detected and controlled by the rectangular wave voltage, the voltage that can be applied to the motor is smaller than when the sine wave drive is performed, so it is difficult to rotate at high load at high load, and efficiency decreases. There was a problem. In general, rectangular wave control is more likely to cause problems due to the generation of high frequencies and lower efficiency than sine wave control. Further, in the technique disclosed in Japanese Patent Laid-Open No. 6-113583, when a signal corresponding to a specific rotational position of the rotary shaft is received, the signal is controlled by a signal based on a rectangular wave at the time of start-up, but since it is switched to a sine wave, the shaft turns around only instantaneously. Therefore, there is a problem that the problems described above cannot be solved.

The present invention has been made to solve the above problems, and an object thereof is to obtain a highly reliable motor control and refrigerating air-conditioning apparatus having stable operability. It is also intended to perform stable and highly efficient motor control in a wide range such as low load, high load, low rotation, and high rotation. It is an object of the present invention to maintain reliable operation and obtain high performance motor control.

[0005]

A motor control device according to claim 1 of the present invention converts a DC voltage into an AC voltage,
A switching circuit composed of one or more switching elements that adjust the voltage supplied to the motor, a current detection unit that detects the current flowing in the motor, and a switching circuit that controls the switching circuit based on the detection result of the current detection unit. A sine wave drive control means that applies a voltage so that the phase current of the motor has a sine wave shape.
A rectangular wave drive control means for applying a 180-degree rectangular wave voltage to each phase of the motor provided in the control unit, and at least the input state, the output state of the switching circuit, the operation command value of the motor, and the operation state of the motor. One is to switch between the sine wave drive control means and the 180-degree rectangular wave drive control means depending on whether or not the current of the current detection section is easily detected.

The motor control device according to claim 2 of the present invention switches between the sine wave drive control means and the 180-degree rectangular wave drive control means depending on the ON time or OFF time of the switching element.

A motor control device according to a third aspect of the present invention is provided with a plurality of current detecting portions, and the current detecting portions are switched and used according to the number of rotations of the motor.

A motor control device according to a fourth aspect of the present invention switches between the sine wave drive control means and the 180-degree rectangular wave drive control means depending on the magnitude of the DC voltage input to the switching circuit.

According to a fifth aspect of the present invention, in a motor control device, a DC voltage is converted into an AC voltage, and a switching circuit composed of one or more switching elements for adjusting the voltage supplied to the motor and a current flowing in the motor. A current detection unit that detects a current, a control unit that controls the switching circuit based on the detection result of the current detection unit, and a motor that controls the motor, and a voltage that is provided in the control unit so that the motor phase current has a sine wave shape. A sine wave drive control means for applying, a rectangular wave drive control means provided in the control section for applying a voltage of a 180-degree rectangular wave to each phase of the motor, and a control by the sine wave drive control means.
A current calculator for comparing the detection results from the current detectors detected at the time of controlling both of the controllers by switching between control by the 80-degree rectangular wave drive controller and comparison of the current calculators. The sine wave drive control means or the 180-degree rectangular wave drive control means is selected according to the above.

A motor control device according to a sixth aspect of the present invention comprises a cycle calculation section for comparing the detection results of each detection timing of the current detection section in a predetermined cycle, and a sine wave is calculated according to the calculation result of the cycle calculation section. The drive and the 180-degree rectangular wave drive are switched.

According to a seventh aspect of the present invention, there is provided a motor control device, comprising an inverter having a switching circuit composed of one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to the motor. A current detection unit that detects a current flowing through the motor, and a control unit that controls the switching circuit based on the detection result of the current detection unit so that the phase current of the motor has a sinusoidal waveform.
The carrier frequency of the inverter is changed so that the current of the current detector can be easily detected.

According to the eighth aspect of the present invention, the motor control device is provided with a plurality of current detection units, and the current detection units are switched according to the carrier frequency of the inverter for supplying current to the motor.

According to a ninth aspect of the present invention, there is provided a motor control device, comprising an inverter having a switching circuit composed of one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to the motor. A current detection unit that detects a current flowing through the motor, and a control unit that controls the switching circuit based on the detection result of the current detection unit so that the phase current of the motor has a sinusoidal waveform.
The bus voltage of the inverter is changed so that the current of the current detector can be easily detected.

According to a tenth aspect of the present invention, the motor control device is provided with a plurality of current detecting portions, and the current detecting portions are switched according to the bus voltage of the inverter supplying the motor with current.

A refrigerating and air-conditioning apparatus according to claim 11 of the present invention uses the motor control device of the present invention, and the motor load is a compressor.

According to a twelfth aspect of the present invention, there is provided a motor control method, comprising a switching circuit including one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to the motor, and one or more switching circuits. In a motor control device including a control unit that generates a drive signal for controlling a switching circuit based on a detection signal of a current flowing through the motor from the current detection unit, a specific detection signal is detected according to an operating state of the motor. A step of selecting a drive waveform signal corresponding to a specific detection signal from a plurality of types of waveform signals stored in advance, and a step of generating the selected waveform signal as a drive signal of a switching circuit. It is a thing.

According to a thirteenth aspect of the present invention, there is provided a motor control method, wherein a DC voltage is converted into an AC voltage and a switching circuit including one or more switching elements for adjusting the voltage supplied to the motor is provided. In a motor control device including a control unit that generates a drive signal that controls a switching circuit based on a detection signal of a current flowing through the motor from the current detection unit, a plurality of pre-stored units is stored according to the operating state of the motor. The step of selecting a specific waveform signal from the waveform signals of the above types, and the step of detecting a specific detection signal corresponding to the selected waveform signal and generating the waveform drive control signal of the switching circuit. .

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 shows a motor control device according to the present invention. 1 to 6 in FIG.
Is a drive unit switching element, 11 is a motor, 7 is a DC power supply, 8 is a control unit which outputs drive signals for the switching elements 1 to 6, 9 is a current detection unit which detects a phase current of the motor, 1
3 is a bus voltage detector.

For example, when one shunt resistor is used in the current detecting section as shown in FIG. 1, the voltage signal including the current signal generated across the shunt resistor becomes a pulse signal synchronized with the ON time of the switching element. , Current detection must be performed within this rise time. For example, the pulse rise time may become short under conditions such as when the motor load is low or when the DC power supply voltage (bus voltage) is high. Detection was difficult. Further, in order to accurately detect the current, it is necessary to use an expensive microcomputer or DSP having a high processing speed.

According to the present invention, a sine wave drive control for applying a voltage so that the phase current of the motor becomes a sine wave depending on the operating condition of the motor and a rectangular wave control for applying a rectangular wave voltage of 180 degrees to each phase are provided. By switching, accurate current detection is possible and highly reliable motor control is possible.

FIG. 10 is a diagram showing an example of a voltage signal including a drive signal of a switching element by the spatial voltage vector method in the case of performing sine wave drive and a current signal generated in the shunt resistance of the current detecting section at that time. 2, FIG. 2 is a diagram showing a state of the waveform in the section A of FIG. 11, and FIG. 8 is a flowchart showing an example of the operation of the inverter control unit 8 of FIG. The numbers such as (100) in FIG. 11 are U-phase and V from the left.
Phase, W phase, where 1 indicates that the upper arm switching element is ON, and 0 indicates that the lower arm switching element is ON. However, in FIGS. 2 and 10, the dead time (Td) for preventing a short circuit between the upper and lower arms of the switching element is omitted for simplicity of description.

In FIG. 10, assuming that the direction in which the vector of Vk rotates clockwise is positive, the motor is generally moved in a certain direction,
For example, to rotate in the CW direction, A → B → ... → F → A
The Vk vector may be rotated by increasing θ so as to move in the section. For example, in FIG. 2, the Vk vector is (1
It is generated by combining the vector of (00) and the vector of (110), and the relationship between θ and t1, t2, t3, t4 can be obtained by the calculation of the following equation. K = Vin / Vdc a1 = t1 × 2 + t4 = (1-Ksin (θ + 60
°)) · T a2 = t2 × 2 = KTsin (60 ° −θ) a3 = t3 × 2 = KTsinθ where Vin is a voltage applied to the motor, Vdc is a bus voltage, and T is a carrier cycle. Since t1 is a section in which the switching elements 4 to 6 and t4 are the ON sections of the switching elements 1 to 3, no current flows through the shunt resistor, so 9
The current detection circuit of a cannot detect the current. For example, when the voltage Vin applied to the motor, which is the output voltage of the inverter circuit, is small, such as when the load is small, or when the bus bar voltage Vdc, which is the input voltage of the inverter, is large, U in FIG.
Switching elements 1, 5 and 6 of p, Vn and Wn phases are ON
Section, which is the command value from the inverter control unit 8, that is, the time t2 at which the U-phase current can be detected
The interval in which the Vp, Wn-phase switching elements 1, 2, 6 are turned on, that is, the time t3 at which the W-phase current can be detected is shortened, and accurate current detection is difficult due to the delay of the current detection unit. Further, in order to detect the current for three phases of U, V and W phases, the U phase current Iu is detected during t2 during one carrier period, the W phase current Iw is detected during t3, and the V phase is From the formula of Iu + Iv + Iw = 0 and the detection results of the U and W phases, V
The phase current Iv is calculated. In this case, two current detection processes occur. The switching from A to F in the vector control of FIG. 10 is performed by the angle θ. When θ = 0-60 °, it is A section, when it is 60-120 °, it is B section,
This θ is calculated by the current detection result. That is, in the case of sine wave drive, current detection is performed twice at t2 and t3 in FIG. 2 and another current is calculated by a simple calculation.

FIG. 3 is a diagram showing an example of drive signal waveforms of the switching elements 1 to 6 during rectangular wave drive control (180-degree energization control), and FIG. 4 during rectangular wave drive control (180-degree energization control). FIG. 4 is a diagram showing an example of a voltage signal including a drive signal of a switching element during one carrier period and a current signal generated in a shunt resistance of a current detection unit at that time. Also,
FIG. 5 shows another example of the 180-degree rectangular wave drive control.
, Two of the switching elements 1 to 6 are always switching, but in FIG. 5, only one is switching. By controlling in this way, it is possible to reduce the switching loss that occurs at the time of switching, so it is possible to perform energy-saving motor control. FIG. 4 shows a state in which the switching element 1 in the upper arm is switched at the carrier frequency in the 180 degree section and the switching element 4 in the lower arm is kept ON in the 180 degree section. in this case,
In order to detect the current for three phases of U, V, and W phases, the U phase current is detected during t2 during one carrier period, and the W phase has the same magnitude as the U phase but the opposite sign. Therefore, since the V phase is calculated from the formula of Iu + Iv + Iw = 0 and the U and W phase detection results, the number of times of detection in the current detection unit is smaller than that in the space voltage vector method, and FIG. The time t2 of can be obtained by a simple equation such as t2 = Vin / Vdc · T, and is longer than the time of t2 or t3 in FIG. That is, in the case of rectangular wave drive, the current is detected once only at t2 in FIG. 4 and the other two currents are calculated by a simple calculation.

FIG. 8 is a flow chart showing an example of the operation of the inverter control unit 8 of FIG. 1, in which a command value S1 of the rotation speed commanded to the motor control device and a current value S2 detected by the current detection unit 9a. Or DC voltage S output from DC power supply 7
3 and the like are determined by the control method determination unit S4 by a method described later. When the rectangular wave drive control is selected as a result of the determination, the rectangular wave signal generator calculates the ON time of the switching element 1-6, outputs a signal to each element as the rectangular wave drive signal output S6, and controls the inverter. . When the sine wave drive is selected as a result of the determination, a sine wave signal is generated S7, and the sine wave drive signal output S8 is sent from the control unit 8 to the inverter circuit. Under the condition that the times t2 and t3 in FIG. 2 are small, for example, when a motor with a small load such as a small current value from the current detection unit S2 is operating, or the detected voltage of the bus voltage detection unit 13 is large, the bus of the inverter is large. When the voltage is large, S4
By selecting the rectangular wave drive by the control method determination unit of 4 and performing the rectangular wave drive, the current detection time t2 can be increased as shown in FIG. 4, the number of times of current detection can be reduced, and the calculation is facilitated. Therefore, it is not necessary to use an expensive detection circuit or a microcomputer, and the current can be accurately detected, so that highly reliable motor control can be performed. That is, the time t2 of the sine wave drive is t2 = 1 from the above equation.
/ 2 * KT * sin (60 ° -θ), on the other hand, in the case of rectangular wave driving, t2 = KT from the above equation. When these two are compared, sin (60 ° -θ) ≦ 1 and therefore t of rectangular wave driving
2 hours longer.

During 180 ° rectangular wave driving, current detection is not performed for a certain period of time, for example, when the motor rotates twice at 2 rps, the signal of t2 shown in FIG. 4 is forcibly sent to the switching element to rotate the motor. After that, it is possible to start current detection by 180-degree rectangular wave drive control, that is, after detecting an accurate current value, automatically switch to sinusoidal wave drive again for efficient control. Needless to say, in the rectangular wave drive in this case, the motor can be rotated while gradually increasing the time t2 or changing the acceleration. As described above, in the operating state in which it is difficult to detect the current in the sine wave driving, by switching to the 180 degree rectangular wave driving for a certain period of time and then returning again, highly reliable and efficient operation can be performed with an inexpensive device.

FIG. 2 is a diagram showing an example of a voltage signal including a drive signal of a switching element by the spatial voltage vector method in the case of performing sine wave drive and a current signal generated in the shunt resistance of the current detection unit at that time. . The current is detected by the current detector between t2 and t3 in FIG. 2 and the result is input as an analog value to the microcomputer or the like in the inverter controller 8 to be calculated and processed. The current detectors 9a, 9b, etc. Has a delay t5, and further, a delay such as a time t6 for processing a signal input to the microcomputer in an analog manner occurs.
The time t2, t3 at which the current can be detected is calculated by, for example, t2 = 1/2 × Vin / Vdc × Tsin (60 ° −θ) ... t3 = 1/2 × Vin / Vdc × Tsinθ ... Required voltage is applied voltage Vin or bus voltage V
t2 <t5 + t6 and t3 <t5 + t6 due to the influence of dc and θ
If so, accurate current detection cannot be performed.

In another configuration of the motor control device according to the present invention, when the control unit 8 for controlling the motor is provided,
The carrier frequency (= 1 / T) of the voltage type inverter is arbitrarily changed, for example, by decreasing the carrier frequency, the ON times t2 and t3 of the switching element are increased,
The current detection times t2 and t3 in FIG. 2 and FIG. 4 are ensured to be times when t2> t5 + t6 and t3> t5 + t6 are satisfied, thereby enabling accurate current detection and enabling highly reliable motor control. Further, as shown in FIG. 12, two types of current detectors, that is, phase current detectors 9a and 9b, are provided, and the current detector 9a having the shunt resistor 12 is used because t2 and t3 increase at a low carrier frequency, for example, less than 6 kHz. On the other hand, at high carrier frequencies, for example, 6 kHz or more, t2 and t3 become small, so that it is possible to appropriately switch the current detection units such as using the current detection unit 9b having the ACCT and not using the shunt. This enables more accurate current detection and reliable operation.

In another configuration of the motor control device according to the present invention, when the control unit 8 for controlling the motor is provided,
The busbar voltage Vdc of the voltage-type inverter is arbitrarily changed, for example, the busbar voltage is reduced to increase the ON times t2 and t3 of the switching element, and the current detection times t2 and t3 in FIGS. 2 and 4 are t2> t5 + t6.
By ensuring the time that t3> t5 + t6 is satisfied, accurate current detection becomes possible and highly reliable motor control becomes possible. 6 and 7 show an example of a configuration for changing the bus voltage. Here, 14 is a diode bridge, 1
Reference numeral 5 is an AC power supply, 16 is a switch such as a relay or a semiconductor switch such as a transistor, 17, 17a and 17b are capacitors, 18 is a reactor, and 19 is a diode. In order to change the bus voltage, as shown in the DC power supply 7 in FIG. 6, a method using a converter that switches between full-wave rectification and voltage doubler rectification by turning the switch 16 OFF / ON, or as shown in the DC power supply 7 in FIG. You can use a large number of methods such as a simple boost converter. It is also possible to change the busbar voltage by changing the number of rotations such that the busbar voltage is lowered at a low rotation speed because the load is small, and the busbar voltage is increased at a high rotation speed because the load is large. Here, the AC power supply 15 in FIGS. 6 and 8 shows a single-phase power supply, but it goes without saying that it can also be used as a three-phase power supply.

Further, as shown in FIG. 11, the phase current detector 9a,
When the bus voltage is small, for example, t2 and t3 are large when the bus voltage is small, for example, t2 and t3 are large. Therefore, when the bus voltage is large, the current detecting unit 9a having the shunt resistor 12 is used. And t3
Therefore, it is possible to switch the current detecting unit appropriately, such as using the current detecting unit 9b having the ACCT and not using the shunt. This enables more accurate current detection and reliable operation.

FIG. 2 is a diagram showing an example of a voltage signal including a drive signal of a switching element by the spatial voltage vector method in the case of performing sine wave drive and a current signal generated in the shunt resistance of the current detection unit at that time. . FIG. 12 shows FIGS.
6 is a flowchart showing an example of the operation of the inverter control unit 8 of FIG. S34 is one of the input state and output state of the switching circuit, such as the rotational speed command value S31, the detected value S32 of the current detection unit, the detected value S33 of the bus voltage detection unit, the command value for motor operation and the operating state Step of selecting sine wave drive or 180 degree rectangular wave drive by one or a combination of detection data. If rectangular wave drive is selected, a rectangular wave signal is generated and ON time is calculated S35, and sine wave drive is selected. If so, generate a sine wave signal and calculate ON time S
37. In any case, this ON time is determined S36,
S38, and outputs the signal if within the current detection time range S3
9, S40.

The ON time during sine wave driving is t in FIG.
The current is detected by the current detector 12 between 2 and t3, and the result is input to a microcomputer or the like in the controller 8 as an analog value for calculation and processing. However, the delay of the current detector (hereinafter: t5 ) And a time (hereinafter referred to as t6) for processing a signal input in analog to the microcomputer. t2 and t3 are, for example, by the microcomputer,
It is obtained by the calculation of the above equation, and t2 <t5 + t6 and t3 <t due to the influence of the applied voltage Vin, the bus voltage Vdc and θ.
When it becomes 5 + t6, accurate current detection cannot be performed.

Further, the ON times t2 and t3 of the switching element are set by the microcomputer in the control unit 8 and the like, and the maximum value of this ON time is a time shorter than the time of one carrier period T, When the maximum value is reached, the voltage applied from the switching unit to the motor saturates, which may lead to a decrease in the number of revolutions and a deterioration in efficiency depending on the conditions of the motor. In general, the voltage that can be applied to the motor is higher in the 180-degree rectangular wave drive than in the sine wave drive. Therefore, in the sine wave drive, the reduction in the rotational speed of the motor and the deterioration in efficiency are more remarkable than in the rectangular wave drive. There is.

In the motor control device according to the present invention, a sine wave drive control for applying a voltage so that the phase current of the motor becomes a sine wave depending on the ON time or the OFF time of the switching element, and the voltage of a 180-degree rectangular wave for each phase. The rectangular wave control for applying is switched. As shown in the flowchart of FIG. 12, the control method determination unit S34 selects 180-degree rectangular wave drive S35 or sine wave drive S37,
Calculate the switching on time and calculate the result as O
The N-time determination units S36 and S38 make the determination and the control method is determined again. The location of the ON time determination unit is arranged between the ON signal generation unit and the signal output in FIG. 13, but it may be arranged at another place, for example, between the control method determination unit, depending on the control method. After receiving the signal from the signal generator or selecting the sine wave drive, the switching element O
Depending on the magnitude of N time t2, t3 or OFF time t1, t4, for example, when the condition of t2 <t5 + t6 is satisfied, the sine wave drive control is switched to the rectangular wave control, and the drive signal of the switching element as shown in FIG. 4 is changed to the rectangular wave drive. Switching t2> t
By setting the current detection time t2 that satisfies 5 + t6, accurate current detection becomes possible and highly reliable motor control becomes possible. As shown in the flowchart of FIG. 13, this switching is always or at a time interval determined from both detection data such as a driving command and feedback based on the determination of ON or OFF time, and an accurate and efficient operation is appropriately selected. It will be.

It is also possible to switch the drive system when the ON time of the switching element reaches a certain value.
For example, when performing rectangular wave drive, Up in FIG.
When the ON time t2 of Vn (= Vin / Vdc · T) exceeds a certain set value, switching to the sine wave drive makes it possible to perform motor control with smooth motor operation and low noise. Conversely, by switching from sine wave drive to 180 degree rectangular wave drive depending on the ON time of the switching element, the voltage applied to the motor can be increased, and highly reliable motor control can be realized.
Although various conditions for switching between the sine wave drive and the rectangular wave drive have been described above, it goes without saying that they may be switched individually or in combination with a plurality of conditions.

In the motor control device as shown in FIG. 11, when the ACCT is used for the phase current detecting portion 9b of the motor, the phase current period becomes small when the rotation speed of the motor is small. Becomes large and accurate current detection cannot be performed.

In the motor control device as shown in FIG. 11, when the ACCT is used for the phase current detector 9b of the motor, the cycle of the phase current becomes small when the rotation speed of the motor is small. The phase shift becomes large and accurate current detection becomes impossible.

A preset rotational speed at which the phase shift of the detection result of the ACCT becomes relatively large, for example, 20 rp
When controlling the motor at less than s, sine wave drive or 180 ° rectangular wave control using the detection result of the current detection unit 9a is performed without using the detection result of the current detection unit 9b, and this rotation speed becomes 20 rps or more. In this case, the sine wave drive is performed using the detection result of the current detector 9b. The rotation speed may be detected by a rotation speed command value or a measurement value that directly measures the rotation speed of the motor.

That is, in the motor control device according to the present invention, the current detecting portion is switched depending on the rotation speed of the motor, so that the motor can be stably driven at low rotation speed. In addition, efficiency can be improved at high speed.

In the present invention, rectangular wave drive control and sine wave drive control may be switched depending on the magnitude of the bus voltage of the inverter. At the time of sine wave driving, t2 and t3 are calculated by the above-mentioned microcomputer or the like using an equation using a bus voltage value, and when the bus voltage is high, t2 and t3 tend to be small. Therefore, when the bus voltage is low, 18
The current detection time t2 can be increased by controlling with a 0-degree rectangular wave and controlling with a sine wave when the bus voltage is above a certain value, so that the current can be accurately detected.

In the motor control device of the present invention, the efficiency when the motor is driven by a sine wave and the efficiency when the motor is driven by a 180-degree rectangular wave differ depending on conditions such as the load of the motor and the number of revolutions. It is difficult to select one efficient and appropriate control method. Generally, when the motor conditions such as load and rotation speed and the inverter circuit conditions such as bus voltage are the same or very close, the smaller the current value flowing in the phase current, the better the motor efficiency. It is advisable to store the current during operation and select the one that has been stored as having a small current during each operation.

According to the present invention, the calculation unit for calculating and comparing the detection result detected by the current detection unit when the motor is driven by the sine wave with the detection result detected by the current detection unit when the rectangular wave control is performed. Is provided in the inverter control unit, and efficient control of the motor is enabled by selecting the control with the smaller current detection result of the sine wave drive or the 180-degree rectangular wave drive according to the calculation result of the calculation unit. For example, both controls may be switched within a fixed time during which the operating conditions do not change, the currents in these two states may be detected by the current detector, and the comparison may be performed. As an example of this, current detection is performed instead of the ON time determination unit in the flowchart of FIG. 12, and thereafter, unlike the figure, the current values of both are compared and a control method with a small current detection result is selected.

FIG. 9 is a flow chart showing another example of the present invention. S23 is a step of obtaining the difference between the detected currents S21 and S22 from the past cycle when the operating state is constant. S24 is a step of determining the control method based on the obtained difference in current value. In the motor control device, sine wave drive is performed by space voltage vector control,
When detecting the phase currents of the three phases of the motor with one shunt resistor, the phase current detection time may become shorter under conditions such as when the motor load is light or when the bus power supply is large. As described above, there are cases where accurate current detection cannot be performed due to the influence of the circuit delay, etc. When the motor is driven by using the current detection result although the accurate current detection result is not obtained, there is a possibility of causing unstable operation of the motor, deterioration of efficiency, and noise.

In the example of the present invention, an arithmetic unit for comparing the detection results at each detection timing of the current detecting unit in a predetermined cycle is provided.
Switch 0 degree rectangular wave drive. For example, a sine wave drive by space voltage vector control is performed to detect the phase currents of three phases of the motor with one shunt resistor, and the arithmetic unit that compares the cycles compares the cycle with a previous current detection result at a certain cycle, for example, every current detection cycle. The absolute value of the difference is calculated, and if the calculation result is a predetermined value, which is greater than or equal to X in step S24 in FIG. When the sine wave drive is performed, each phase current of the motor becomes a sine wave,
The detection result of the current detector is also a sine wave. It is estimated that the absolute value of the difference between the previous current detection result and the current detection result of the arithmetic unit is less than a predetermined value. When the absolute value of the difference between the previous current detection result and the current detection result of the calculation unit exceeds a predetermined value, the current is disturbed by the detection result of the current detection unit or the condition of the motor or the control unit. Therefore, the current can be accurately detected by switching to the 180-degree rectangular wave drive, which is reliable and easy to detect the current, and enables highly reliable motor control.

FIG. 13 is a flow chart showing another example of the operation of the inverter control unit 8 shown in FIG. Figure 1
Reference numeral 2 denotes a phase current detection circuit as a detection signal for generating a drive signal to the inverter control unit 8, for example, a current signal from the phase current detection circuit 9b and another phase current detection circuit, for example, from the phase current detection circuit 9a. The current signal can be detected. S41 is a rotation speed command value that is the rotation speed to be operated in the inverter control unit 8, S42 is a current detection unit 9b,
9a is a detection signal of a current value, S43 is a DC voltage from the bus voltage detection unit 13, S44 is a condition set in the microcomputer or the like in the inverter control unit 8 such as the load state and the rotation speed of the motor as described above. A detection section selecting section for selecting a detection signal for driving signal generation, S45 is a driving wave signal selecting section for determining a control method of sine wave driving or 180 degree rectangular wave driving, and S46 is a 180 degree rectangular wave driving. A 180-degree rectangular wave signal generation unit for selecting control and calculating the ON time of the switching element based on the detection signal, S47
Outputs a 180-degree rectangular wave control signal from the inverter control unit 8. S48 is a sine wave signal generation unit that selects sine wave drive control and calculates the ON time of the switching element based on the current value from the phase current detection circuit as a feedback detection signal. S49 is a sine wave drive signal as an inverter drive signal. Output. S50 selects a certain phase current detection circuit and calculates the ON time of the switching element based on this signal, and the 180 degree rectangular wave signal generation section, and S51 outputs the 180 degree rectangular wave drive signal as an inverter drive signal.

In the motor control method relating to FIG. 13, a switching circuit composed of one or more switching elements for converting a DC voltage into an AC voltage and adjusting the voltage supplied to the motor, and at least one of the currents flowing through the motor. Step S44 of detecting a specific detection signal according to the operating state of the motor to the motor control device including a control unit that generates a drive signal that controls the switching circuit by one detection signal, and the specific detection signal Step S45 of selecting a drive waveform signal corresponding to the above from a plurality of types of waveform signals stored in advance in the microcomputer of the inverter control unit or the like.
And steps S46, S48 and the like for generating the selected waveform signal as a drive signal for the switching circuit. As a result, a drive signal suitable for a condition such as a load state is selected and used, so that the motor can be operated with high accuracy and high reliability.

FIG. 14 is a flow chart showing still another example of the operation of the inverter controller 8 shown in FIG.
S61 is a rotation speed command value that is the rotation speed to be operated in the inverter control unit 8, and S62 is current detection units 9b and 9a.
Detection signal of the detection unit typified by the current value from S, S63 is a DC voltage from the bus voltage detection unit 13, and S64 is a drive for determining which of the preset waveform control methods of the waveform drive control is selected. Wave signal selection unit, S65 is 18
A detection unit selection unit that selects 0 ° rectangular wave drive control and selects a detection signal for this, S66 is a certain current detection unit 1, for example, a switching element is turned on based on the phase current detection circuit 9b.
A rectangular wave signal generation unit that calculates time and generates a 180-degree rectangular wave signal, and S67 outputs a 180-degree rectangular wave control signal from the inverter control unit 8. In S68, the rectangular wave drive control is selected, and as a detection signal, the switching element O
180 degree rectangular wave signal generator for calculating N hours, S
69 outputs a 180-degree rectangular wave drive signal as an inverter drive signal. S70 outputs a sine wave drive signal from the inverter control section to the inverter circuit in S70, and the sine wave signal generation section generates a sine wave signal when sine wave drive control is selected.

The motor control method relating to FIG. 14 of the present invention includes a switching circuit composed of one or more switching elements for converting a DC voltage into an AC voltage and adjusting the voltage supplied to the motor, and a current flowing through the motor. And a control unit for generating a drive signal for controlling the switching circuit based on at least one detection signal of the inverter control unit 8 according to the operating state of the motor such as the load state and the rotation speed. Step S64 of preferentially selecting a waveform signal from which a sinusoidal drive can be obtained so as to reduce noise when there is a problem of noise from a plurality of types of waveform signals stored in the microcomputer and the selected waveform. A specific detection signal corresponding to the signal is detected and S6
5, step S66 for generating a waveform drive control signal for the switching circuit, and the like. As a result, a highly efficient operation method capable of reliable operation can be obtained.

The control contents may be preferentially selected from the above various control contents in accordance with a specific use or purpose. As a result, load, rotation speed, accuracy and stable operation, various conditions such as product price, vibration, noise, etc. This is a convenient control device and method that can flexibly pursue the best even if the state changes during operation Is obtained,
Easy-to-use control when optimal operation is required not only for the entire operating range but also for the time elapsed from the start of operation to the state of being in the state of being contaminated just before disposal for energy saving and environmental protection such as air conditioners. Is obtained. That is, according to the present invention, by using the motor control device as a control device for a compressor such as an air conditioner or a refrigerator, the motor control device is inexpensive and has stable motor startability, and a highly efficient compression is achieved even under high load and high rotation. It becomes possible to control the machine. In the refrigeration cycle of refrigerators and air conditioners, natural refrigerants such as hydrocarbons and carbon dioxide and refrigerants such as CFC substitutes are discharged by a compressor and circulated in the condenser and evaporator. It produces cold air for cooling and freezing. The air conditioner enables heating and cooling of the room. There are various types of heat source devices such as compressors used in these refrigeration and air-conditioning systems such as reciprocating, rotary, scroll, and pump, and in either method, the refrigerant is compressed and discharged into the refrigeration cycle or circulated. In the process of generating, a large load torque is generated and only a small load torque is generated when the refrigerant is mainly sucked, such as while compressing, and a variation cycle of the load torque is always generated by the rotation of the motor. In a compressor motor such as a motor that drives a fan, which does not have a constant acceleration state and always produces a torque cycle, the physical quantity to be measured is also affected by this cycle. When is the detected value of the operating state, the effect of this cycle fluctuation is reduced. Further, by using the control device of the present invention for the motor having the compressor of the refrigerating and air-conditioning system as a load, the control can be switched between drive waveform control and sine waveform control no matter what detection data is obtained. Therefore, the torque fluctuation is large like a compressor and the motor is apt to become unstable,
Further, even if the load is apt to cause abnormal noise or the like, it is possible to continue the highly reliable operation by the flexible control capable of continuously or intermittently responding.

The motor control device according to the present invention comprises a voltage type inverter having a switching circuit composed of a plurality of switching elements for adjusting the voltage supplied to the motor, and a current detecting section for detecting the current flowing through the motor. The present invention relates to a device for controlling the motor, which is a sine wave drive control that applies a voltage so that the phase current of the motor becomes a sine wave and a rectangular wave that applies a voltage of a 180-degree rectangular wave to each phase, depending on the operating conditions of the motor. Switch between control and.

Further, in the motor controller, the carrier frequency of the inverter is changed under certain predetermined conditions. Further, the sine wave drive control and the 180-degree rectangular wave control are switched depending on the ON time or the OFF time of the switching element. Further, the sine wave drive control and the rectangular wave control are switched according to a predetermined rotation number of the motor. Further, the sine wave drive control and the rectangular wave control are switched depending on the magnitude of the bus voltage of the inverter.

Further, according to the present invention, in the motor control device, the current value detected when the motor is sinusoidally driven and the current value detected from the current detection unit when the 180-degree rectangular wave control is performed are calculated. An arithmetic unit for comparison is provided, and sine wave drive and rectangular wave drive are switched according to the arithmetic result of the arithmetic unit.

In the control device of the present invention, an arithmetic unit for comparing the detection result of each detection timing of the current detecting unit in a predetermined cycle is provided, and the sine wave drive and the 180-degree rectangular wave drive are performed according to the arithmetic result of the arithmetic unit. Switch. Further, the motor controller of the present invention is used for a compressor controller such as an air conditioner.

In the motor control device of the present invention, the sine wave drive control for applying a voltage so that the phase current of the motor becomes a sine wave depending on the operating conditions of the motor, and the rectangular shape for applying a voltage of a 180-degree rectangular wave to each phase. By switching between wave control and wave control, accurate current detection is possible and highly reliable motor control is possible.

In the motor control device of the present invention, the ON time of the switching element is increased by arbitrarily changing the carrier frequency of the voltage type inverter, and the current detection time is increased to enable accurate current detection, which is reliable. It enables highly efficient motor control.

In the motor control device of the present invention, the ON time of the switching element is increased by arbitrarily changing the bus voltage of the inverter of the voltage type inverter, and the current detection time is increased to enable accurate current detection. This enables highly reliable motor control.

In the motor control device according to the present invention, accurate current detection becomes possible by switching between sinusoidal wave drive control and 180-degree rectangular wave control depending on the ON time or OFF time of the switching element, and highly reliable motor control is possible. It is possible.

In the motor control device according to the present invention, the 180-degree rectangular wave drive and the sine wave drive are switched depending on the number of rotations of the motor to enable stable motor drive at low rotation speeds.

In the motor control device according to the present invention, the current detection time can be increased by switching the 180-degree rectangular wave drive control and the sine wave drive control depending on the magnitude of the bus voltage of the inverter, so that the current can be accurately detected. can do.

In the motor control device according to the present invention, the detection result detected by the current detection unit when the sine wave drive of the motor is performed and the detection result detected by the current detection unit when the 180-degree rectangular wave control is performed. And a sine wave drive based on a calculation result of the calculation unit.
By selecting the control with the smaller current detection result of the 0-degree rectangular wave drive, efficient motor control is possible.

In the motor control device according to the present invention, there is provided an arithmetic unit for comparing the detection result of each detection timing of the current detecting unit in a predetermined cycle, and the sine wave drive and the 180-degree rectangular wave are calculated according to the arithmetic result of this arithmetic unit. By switching the drive, it is possible to accurately and accurately detect the current by switching to the 180-degree rectangular wave drive, in which the current detection is reliable and easy, which enables highly reliable motor control.

According to the present invention, the motor control device is used as a control device for a compressor such as an air conditioner or a refrigerator, so that the motor has inexpensive and stable motor operability and high efficiency even under high load and high rotation. It is possible to control various compressors.

[0062]

According to the first aspect of the present invention, there is provided a motor control device, which includes a switching circuit including one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to the motor, and a motor. Current detecting section for detecting the current flowing through the control circuit, a control section for controlling the switching circuit based on the detection result of the current detecting section and controlling the motor, and a phase current of the motor provided in the control section so that the phase current of the motor becomes sinusoidal. A sine wave drive control means for applying a voltage and a rectangular wave drive control means for applying a voltage of a 180-degree rectangular wave to each phase of the motor, which is provided in the control unit, are provided, and the input state, the output state of the switching circuit, the motor Of the sine wave drive control means and the rectangular wave drive control means depending on whether at least one of the operation command value of the motor and the operating state of the motor easily detects the current of the current detector. Since, stable operation becomes possible reliable motor control is obtained over the entire operating range.

Since the motor control device according to claim 2 of the present invention switches between the sine wave drive control means and the 180-degree rectangular wave drive control means according to the ON time or OFF time of the switching element, accurate current detection is possible. is there.

In the motor control device according to the third aspect of the present invention, the current detecting portion is switched and used depending on the rotation speed of the motor, so that the motor can be stably driven at a low rotation speed. Further, the efficiency at high speed can be improved.

In the motor control device according to claim 4 of the present invention, the sine wave drive control means and the 180-degree rectangular wave drive control means are switched according to the magnitude of the DC voltage input to the switching circuit, so that the configuration is simple. Accurate current is obtained.

According to a fifth aspect of the present invention, in the motor control device, the motor is driven by switching between control by the sine wave drive control means and control by the 180-degree rectangular wave drive control means, and when both control means are controlled. A current calculation unit that compares the detected results from the detected current detection unit, and since the sine wave drive control unit or the rectangular wave drive control unit is selected according to the comparison of the current calculation units, motor control is always efficient. Is obtained.

A motor control device according to a sixth aspect of the present invention comprises a cycle calculation section for comparing the detection results of each detection timing of the current detection section in a predetermined cycle, and a sine wave is calculated according to the calculation result of the cycle calculation section. Since the drive and the 180-degree rectangular wave drive are switched, highly reliable motor control can be obtained.

According to a seventh aspect of the present invention, there is provided a motor control device, which includes an inverter having a switching circuit which is formed of one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to the motor. A current detection unit that detects a current flowing through the motor, and a control unit that controls the switching circuit based on the detection result of the current detection unit so that the phase current of the motor has a sinusoidal waveform.
Since the carrier frequency of the inverter is changed so that the current of the current detector can be easily detected, a highly accurate and highly reliable device can be obtained.

The motor control device according to claim 8 of the present invention is provided with a plurality of current detectors, and the current detectors are switched according to the carrier frequency of the inverter for supplying the current to the motor. Is obtained.

According to a ninth aspect of the present invention, there is provided a motor control device, comprising an inverter having a switching circuit which is configured by one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to the motor. A current detection unit that detects a current flowing through the motor; and a control unit that controls the switching circuit based on a detection result of the current detection unit and controls the phase current of the motor to be sinusoidal. Since the bus voltage of the inverter is changed so that the current of the current detection unit can be easily detected, an accurate and highly reliable device can be obtained.

Since the motor control device according to claim 10 of the present invention is provided with a plurality of current detecting portions and is used by switching the current detecting portion according to the bus voltage of the inverter for supplying current to the motor, the motor controlling device can be used reliably. Signal is obtained.

A refrigerating and air-conditioning apparatus according to claim 11 of the present invention uses the motor control device of the present invention, and the load of the motor is a compressor. Therefore, even a machine having large fluctuations can be operated reliably in a wide range. The device is obtained.

According to a twelfth aspect of the present invention, in a motor control method, a DC voltage is converted into an AC voltage, and a switching circuit composed of one or more switching elements for adjusting the voltage supplied to the motor and a current flowing through the motor. In a motor control device including a control unit that generates a drive signal that controls a switching circuit by at least one detection signal of a current, a step of detecting a specific detection signal according to an operating state of the motor, The step of selecting a drive waveform signal corresponding to the detection signal from a plurality of types of waveform signals stored in advance and the step of generating the selected waveform signal as the drive signal of the switching circuit are provided, so that the efficiency is improved. A control method capable of stable operation is obtained.

According to a thirteenth aspect of the present invention, there is provided a motor control method, wherein a DC voltage is converted into an AC voltage and a switching circuit constituted by one or more switching elements for adjusting the voltage supplied to the motor and a current flowing through the motor. In a motor control device including a control unit that generates a drive signal that controls a switching circuit by at least one detection signal of a current, a plurality of types of waveform signals that are stored in advance according to the operating state of the motor are used. With the step of selecting a specific waveform signal and the step of detecting a specific detection signal corresponding to the selected waveform signal and generating the waveform drive control signal of the switching circuit, noise is low and reliability is high. A control method is obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a motor control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of signal waveforms of respective parts of the motor control device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a rectangular wave drive signal waveform that is an embodiment of the present invention.

FIG. 4 is an explanatory diagram of a rectangular wave drive signal waveform that is an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a 180-degree rectangular wave drive signal waveform that is an embodiment of the present invention.

FIG. 6 is a configuration diagram of a motor control device according to an embodiment of the present invention.

FIG. 7 is a configuration diagram of a motor control device according to an embodiment of the present invention.

FIG. 8 is a flowchart showing an operation of the motor control device according to the embodiment of the present invention.

FIG. 9 is a flowchart showing an operation of the motor control device according to the embodiment of the present invention.

FIG. 10 is an explanatory diagram of a space vector control method according to an embodiment of the present invention.

FIG. 11 is a configuration diagram of a motor control device according to an embodiment of the present invention.

FIG. 12 is a flowchart showing an operation of the motor control device according to the embodiment of the present invention.

FIG. 13 is a flowchart showing an operation of the motor control device according to the embodiment of the present invention.

FIG. 14 is a flowchart showing an operation of the motor control device according to the embodiment of the present invention.

FIG. 15 is a configuration diagram of a conventional motor control device.

FIG. 16 is a configuration diagram of a conventional motor control device.

[Explanation of symbols]

1,2,3,4,5,6 drive part switching element,
7 DC power supply, 8 control section, 9 current detection circuit, 1
0 induced voltage detector, 11 motor, 12 shunt resistor, 13 bus voltage detector, 14 diode bridge, 15 AC power supply, 16 switch, 1
7, 17a, 17b capacitors, 18 reactors,
19 diode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Makoto Hirano             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 5H576 AA10 BB02 BB06 DD02 EE19                       EE30 FF07 FF08 GG04 GG07                       HA04 HB02 JJ03 LL22

Claims (13)

[Claims] 1. A switching circuit configured by one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to a motor; a current detection unit for detecting a current flowing through the motor; A control unit that controls the switching circuit based on the detection result of the current detection unit and controls the motor, and a sine wave drive that is provided in the control unit and applies a voltage so that the phase current of the motor has a sine wave shape. Control means, and 180 degree rectangular wave drive control means for applying a voltage of a 180 degree rectangular wave to each phase of the motor, which is provided in the control section, and includes an input state and an output state of the switching circuit, The sine wave drive control means and the 180-degree quadrature depending on whether at least one of the operation command value and the operation state of the motor can easily detect the current of the current detector. A motor control device characterized by switching between a square wave drive control means. 2. The sine wave drive control means and the 180 depending on ON time or OFF time of the switching element.
2. The motor control device according to claim 1, wherein the control unit switches between the rectangular wave drive control means. 3. The motor control device according to claim 1, wherein a plurality of current detectors are provided, and the current detectors are switched and used according to the rotation speed of the motor. 4. The motor control according to claim 1, wherein the sine wave drive control means and the 180-degree rectangular wave drive control means are switched according to the magnitude of the DC voltage input to the switching circuit. apparatus. 5. A switching circuit configured by one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to a motor, a current detection unit for detecting a current flowing through the motor, and A control unit that controls the switching circuit based on the detection result of the current detection unit and controls the motor, and a sine wave drive that is provided in the control unit and applies a voltage so that the phase current of the motor has a sine wave shape. Control means, 180 degree rectangular wave drive control means provided in the control section for applying a voltage of 180 degree rectangular wave to each phase of the motor, and control by the sine wave drive control means,
A current calculation unit that switches the control by the 180-degree rectangular wave drive control unit to drive the motor and compares the detection results from the current detection unit detected during the control of both the control units. A motor control device, characterized in that the sine wave drive control means or the 180-degree rectangular wave drive control means is selected in accordance with a comparison of arithmetic units. 6. A cycle calculation section for comparing the detection result of each detection timing of the current detection section in a predetermined cycle,
6. The motor control device according to at least one of claims 1 to 5, wherein the sine wave driving means and the 180-degree rectangular wave driving means are switched according to the calculation result of the cycle calculating portion. 7. An inverter provided with a switching circuit configured to convert a DC voltage into an AC voltage and adjusting a voltage supplied to a motor, and a current detection for detecting a current flowing through the motor. And a control unit that controls the switching circuit based on the detection result of the current detection unit so that the phase current of the motor has a sine wave shape, and detects the current of the current detection unit. A motor control device characterized in that the carrier frequency of the inverter is changed so as to be easy. 8. At least one of claims 1 to 7, characterized in that a plurality of current detectors are provided and the current detectors are switched according to a carrier frequency of an inverter for supplying a current to the motor. 1. The motor control device described in 1. 9. An inverter provided with a switching circuit configured to convert a DC voltage into an AC voltage and adjusting a voltage supplied to a motor, and a current detection for detecting a current flowing through the motor. And a control unit that controls the switching circuit based on the detection result of the current detection unit so that the phase current of the motor has a sine wave shape, and detects the current of the current detection unit. A motor control device characterized in that the bus voltage of the inverter is changed so as to be easy. 10. At least one of claims 1 to 9 characterized in that a plurality of current detecting sections are provided and the current detecting section is switched according to the bus voltage of an inverter for supplying a current to the motor. 1. The motor control device described in 1. 11. A refrigerating and air-conditioning apparatus using the motor control device according to at least one of claims 1 to 10, wherein a load of the motor is a compressor. 12. A switching circuit composed of one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage supplied to the motor, and a current flowing through the motor from one or more current detection units. A control unit for generating a drive signal for controlling the switching circuit according to the detection signal, and a step of detecting a specific detection signal according to an operating state of the motor; A step of selecting a drive waveform signal corresponding to the signal from a plurality of types of waveform signals stored in advance, and a step of generating the selected waveform signal as a drive signal of the switching circuit. Motor control method. 13. A switching circuit composed of one or more switching elements for converting a DC voltage into an AC voltage and adjusting a voltage to be supplied to the motor, and a current flowing through the motor from one or more current detectors. A control unit for generating a drive signal for controlling the switching circuit according to the detection signal of 1., in a motor control device including a plurality of types of waveform signals stored in advance in accordance with an operating state of the motor. A method of controlling a motor, comprising: a step of selecting a waveform signal; and a step of detecting a specific detection signal corresponding to the selected waveform signal and generating a waveform drive control signal of the switching circuit. .