Patent Description:
In the related art, a motor drive device using a three-phase alternating current as a power source has been known (see, for example, PTL <NUM>).

In a case where there is a phase loss in the three-phase alternating current serving as the power source, when a load of the motor to be driven is relatively large, the motor drive device may not be able to normally drive the motor.

Thus, when there is a possibility that the motor cannot be normally driven due to a phase loss in the three-phase alternating current serving as the power source, it is desirable not to drive the motor.

<CIT> discloses a motor drive device configured to drive a motor using a three-phase alternating current and comprising a rectifier circuit, a current detection circuit to detect the rectified current; a cross point detection circuit to detect a cross point between the rectified current detected by the current detection circuit and a predetermined current value, and to output a control signal indicating whether or not to drive the motor; and a smoothing circuit to generate a smoothed current; wherein the cross point detection circuit outputs the control signal indicating that the motor is not to be driven in a case where a number of times of the detection of the cross point in one cycle of the three-phase alternating current is <NUM>, the cross point detection circuit further outputs the control signal indicating that the motor is to be driven where the number of times of the detection of the cross point in one cycle of the three-phase alternating current is <NUM>. Further relevant background art is disclosed in <CIT>, <CIT>, <CIT> and <CIT>.

Therefore, an object of the present disclosure is to provide a motor drive device capable of outputting a control signal not to drive a motor in a case where there is a possibility that the motor cannot be normally driven due to a phase loss in a three-phase alternating current serving as a power source.

A motor drive device according to the present disclosure is a motor drive device that drives a motor using a three-phase alternating current as a power source. The motor drive device includes a rectifier circuit that rectifies the three-phase alternating current to generate a direct current, a current detection circuit that detects the direct current rectified by the rectifier current, and a cross point detection circuit that detects a cross point between the direct current detected by the current detection circuit and a predetermined current value, and outputs a control signal indicating whether or not to drive the motor based on a result of the detection.

As a result, in a case where there is a possibility that the motor cannot be normally driven due to a phase loss in the three-phase alternating current serving as the power source, the motor drive device capable of outputting the control signal not to drive the motor is provided.

Hereinafter, a specific example of a motor control device according to the present disclosure will be described with reference to the drawings. Note that exemplary embodiments to be described below each illustrate a specific example of the present disclosure. Numerical values, shapes, constituent components, arrangement positions and connection modes of the constituent components, steps, order of the steps, and the like illustrated in the following exemplary embodiments are merely examples. Further, each of the drawings is a schematic view, and is not necessarily precisely illustrated.

Note that the comprehensive or specific aspects of the present disclosure may be implemented by a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a compact disk read only memory (CD-ROM), or may be implemented by any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

<FIG> is a block diagram illustrating a configuration of motor drive system <NUM> according to a first exemplary embodiment.

As illustrated in <FIG>, motor drive system <NUM> includes motor drive device <NUM>, three-phase alternating current power supply <NUM>, motor <NUM>, and display device <NUM>.

Motor <NUM> is driven by motor drive device <NUM>.

three-phase alternating current power supply <NUM> supplies a three-phase alternating current including three phases of an L1 phase, an L2 phase, and an L3 phase to motor drive device <NUM>.

Display device <NUM> displays an image based on a control signal (to be described later) output from motor drive device <NUM>.

Motor drive device <NUM> uses, as a power source, the three-phase alternating current supplied from three-phase alternating current power supply <NUM> to drive motor <NUM>.

As illustrated in <FIG>, motor drive device <NUM> includes rectifier circuit <NUM>, current detection circuit <NUM>, cross point detection circuit <NUM>, inverter <NUM>, and smoothing circuit <NUM>.

Rectifier circuit <NUM> rectifies the three-phase alternating current supplied from three-phase alternating current power supply <NUM>. Hereinafter, a direct current rectified by rectifier circuit <NUM> and not smoothed by smoothing circuit <NUM> to be described below is also referred to as an "unsmoothed direct current".

The unsmoothed direct current rectified by rectifier circuit <NUM> is supplied to smoothing circuit <NUM>, and the supplied unsmoothed direct current is smoothed. Hereinafter, the direct current smoothed by smoothing circuit <NUM> is also referred to as a "smoothed direct current".

The smoothed direct current smoothed by smoothing circuit <NUM> is supplied to inverter <NUM> to drive motor <NUM>. More specifically, inverter <NUM> converts the supplied smoothed direct current into a three-phase alternating current, and supplies the converted three-phase alternating current to motor <NUM> to drive motor <NUM>.

When a load of motor <NUM> increases, a power of the three-phase alternating current supplied from inverter <NUM> to motor <NUM> increases. Thus, a voltage drop of the smoothed direct current supplied to inverter <NUM> increases.

In a case where the smoothed direct current is converted into the three-phase alternating current, when a control signal (to be described later) indicating that the motor <NUM> is not to be driven is input from cross point detection circuit <NUM>, inverter <NUM> stops the conversion into the three-phase alternating current.

In a case where the conversion into the three-phase alternating current is stopped, when a control signal (to be described later) indicating that the motor <NUM> is to be driven is input from cross point detection circuit <NUM>, inverter <NUM> starts the conversion into the three-phase alternating current.

<FIG> is a waveform diagram illustrating a voltage waveform in a low load state in a case where there is no phase loss in the three-phase alternating current. <FIG> is a waveform diagram illustrating a voltage waveform in a high load state in a case where there is no phase loss in the three-phase alternating current.

<FIG> is a waveform diagram in a state (hereinafter, also referred to as a "low load state") where a relatively small load with which a voltage drop does not occur is applied to motor <NUM> only until a voltage of the smoothed direct current is greater than or equal to a minimum voltage of the unsmoothed direct current in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>. <FIG> is a waveform diagram in a state (hereinafter, also referred to as a "high load state") where a relatively large load with which a voltage drop occurs is applied to motor <NUM> until the voltage of the smoothed direct current is less than the minimum voltage of the unsmoothed direct current in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>.

<FIG> is a waveform diagram illustrating a voltage waveform in a low load state in a case where there is a phase loss in the three-phase alternating current. <FIG> is a waveform diagram illustrating a voltage waveform in a high load state in a case where there is a phase loss in the three-phase alternating current.

In <FIG>, <FIG>, a vertical axis represents a voltage, and a horizontal axis represents a time. L1-L2, L2-L3, and L3-L1 are a voltage difference between the L1 phase and the L2 phase, a voltage difference between the L2 phase and the L3 phase, and a voltage difference between the L3 phase and the L1 phase, respectively. Vrec is a voltage of the unsmoothed direct current rectified by rectifier circuit <NUM>. Vpn is a voltage of the smoothed direct current smoothed by smoothing circuit <NUM>.

Referring back to <FIG>, the description of motor drive device <NUM> will be continued.

Current detection circuit <NUM> detects a current of the unsmoothed direct current rectified by rectifier circuit <NUM>.

Cross point detection circuit <NUM> detects a cross point between the current detected by current detection circuit <NUM> and a predetermined current value (here, the predetermined current value is set to <NUM> [A]. The cross point refers to a state where the current detected by current detection circuit <NUM> and the predetermined current value have the same value. Here, cross point detection circuit <NUM> detects the cross point by detecting a change point at which the current detected by current detection circuit <NUM> changes from a state of the predetermined current value or less to a state of the predetermined current value or more.

Further, cross point detection circuit <NUM> outputs a drive signal indicating whether or not to drive motor <NUM> based on a detection result of the cross point. More specifically, cross point detection circuit <NUM> outputs (<NUM>) a control signal indicating that the motor <NUM> is not to be driven in a case where the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM>, and outputs (<NUM>) a control signal indicating that the motor <NUM> is to be driven in a case where the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM> or <NUM>. The reason why cross point detection circuit <NUM> outputs the drive signal in this manner is that the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM>, which is detected by cross point detection circuit <NUM>, is <NUM> in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, and the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM>, which is detected by cross point detection circuit <NUM>, in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>, is <NUM> or <NUM>. That is, cross point detection circuit <NUM> outputs a control signal indicating that the motor <NUM> is not to be driven to rectifier circuit <NUM> in a case where there is a phase loss in the three-phase alternating current input, and outputs a control signal indicating that the motor <NUM> is to be driven to rectifier circuit <NUM> in a case where there is no phase loss in the three-phase alternating current input.

Hereinafter, the reason why the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM>, which is detected by cross point detection circuit <NUM>, is <NUM> in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, and the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM>, which is detected by cross point detection circuit <NUM> is <NUM> or <NUM> in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM> will be described with reference to the drawings.

<FIG> is a waveform diagram illustrating a current waveform and the number of times of detection of a cross point in a low load state in a case where there is no phase loss in the three-phase alternating current. <FIG> is a waveform diagram illustrating a current waveform and the number of times of detection of a cross point in a high load state in a case where there is no phase loss in the three-phase alternating current.

<FIG> is a waveform diagram illustrating a current waveform and the number of times of detection of a cross point in a low load state in a case where there is a phase loss in the three-phase alternating current. <FIG> is a waveform diagram illustrating a current waveform and the number of times of detection of a cross point in a high load state in a case where there is a phase loss in the three-phase alternating current.

As illustrated in <FIG>, in a case where the load of motor <NUM> is in a low load state, when there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>, the voltage drop occurs only until the voltage of the smoothed direct current is greater than or equal to the minimum voltage of the unsmoothed direct current. Thus, the current flowing from rectifier circuit <NUM> to smoothing circuit <NUM>, that is, the current detected by current detection circuit <NUM> constantly has a current value of <NUM> [A] <NUM> times in one cycle of the three-phase alternating current input to rectifier circuit <NUM> as illustrated in <FIG>. Thus, as illustrated in <FIG>, cross point detection circuit <NUM> detects the cross point six times in one cycle of the three-phase alternating current input to rectifier circuit <NUM>.

As illustrated in <FIG>, in a case where the load of motor <NUM> is in a high load state, when there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>, the voltage drop occurs until the voltage of the smoothed direct current is less than the minimum voltage of the unsmoothed direct current. Thus, the current value of the current flowing from rectifier circuit <NUM> to smoothing circuit <NUM>, that is, the current detected by current detection circuit <NUM> does not become <NUM> [A] in one cycle of the three-phase alternating current input to rectifier circuit <NUM> as illustrated in <FIG>. Thus, as illustrated in <FIG>, cross point detection circuit <NUM> detects the cross point <NUM> times in one cycle of the three-phase alternating current input to rectifier circuit <NUM>.

As described above, in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>, cross point detection circuit <NUM> constantly detects the cross point <NUM> times or <NUM> times in one cycle of the three-phase alternating current input to rectifier circuit <NUM>.

As illustrated in <FIG>, in both a case where the load of motor <NUM> is in a low load state and a case where the load of motor <NUM> is in a high load state, when there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, the voltage of the smoothed direct current decreases to <NUM> [V]. Thus, the current flowing from rectifier circuit <NUM> to smoothing circuit <NUM>, that is, the current detected by current detection circuit <NUM> constantly has a current value of <NUM> [A] twice in one cycle of the three-phase alternating current input to rectifier circuit <NUM> as illustrated in <FIG>. Thus, as illustrated in <FIG>, cross point detection circuit <NUM> constantly detects the cross point twice in one cycle of the three-phase alternating current input to rectifier circuit <NUM>.

Hereinafter, motor stop processing performed by motor drive system <NUM> having the above configuration will be described.

The motor stop processing is processing of stopping the drive of motor <NUM> when the phase loss occurs in the three-phase alternating current supplied from three-phase alternating current power supply <NUM> in a case where motor drive device <NUM> drives motor <NUM>.

Motor drive device <NUM> starts driving motor <NUM>, and thus, the motor stop processing is started, for example.

<FIG> is a flowchart illustrating the motor stop processing.

When the motor stop processing is started, cross point detection circuit <NUM> checks whether the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM> (step S10).

In the processing of step S10, in a case where the number of times of detection of the cross point is not <NUM> (No in step S10), cross point detection circuit <NUM> returns to the processing of step S10 again and repeats the processing of step S10.

In the processing of step S10, in a case where the number of times of detection of the cross point to be detected is <NUM> (Yes in step S10), cross point detection circuit <NUM> outputs a control signal not to drive motor <NUM> (step S20).

When the control signal indicating that the motor <NUM> is not to be driven is output, inverter <NUM> stops the conversion of the smoothed direct current into the three-phase alternating current supplied to motor <NUM> (step S30).

When the conversion into the three-phase alternating current supplied to motor <NUM> is stopped, motor <NUM> is stopped (step S40).

When the control signal indicating that the motor <NUM> is not to be driven motor <NUM> is output, since there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, the display device <NUM> displays that motor <NUM> is stopped (step S50).

When the processing of step S50 is ended, motor drive system <NUM> ends the motor stop processing.

As described above, in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, motor drive device <NUM> outputs the control signal indicating that the motor <NUM> is not to be driven. As described above, according to motor drive device <NUM> having the above configuration, in a case where there is a possibility that motor <NUM> cannot be normally driven due to a phase loss in the three-phase alternating current serving as the power source, the control signal indicating that the motor <NUM> is not to be driven can be output.

Hereinafter, a motor drive device according to a second exemplary embodiment configured such that a part of motor drive device <NUM> according to the first exemplary embodiment is changed will be described.

Hereinafter, in the motor drive device according to the second exemplary embodiment, components similar to the components of motor drive device <NUM> will be denoted by the same reference marks as those already described, detailed description thereof will be omitted, and differences from motor drive device <NUM> will be mainly described.

<FIG> is a block diagram illustrating a configuration of motor drive system 1A according to the second exemplary embodiment.

As illustrated in <FIG>, motor drive system 1A is configured such that motor drive device <NUM> of motor drive system <NUM> according to the first exemplary embodiment is changed to motor drive device 10A. Motor drive device 10A is configured such that cross point detection circuit <NUM> of motor drive device <NUM> is changed to cross point detection circuit 13A.

Cross point detection circuit <NUM> according to the first exemplary embodiment has a configuration in which a predetermined current value is set to <NUM> [A]. On the other hand, cross point detection circuit 13A has a configuration in which a predetermined current value is set to a positive value X [A]. Here, predetermined current value X [A] which is a positive value is a maximum value of the current flowing from rectifier circuit <NUM> to smoothing circuit <NUM> in a case where a load with which motor <NUM> can be normally driven is applied to motor <NUM> even though there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>. As a result, according to cross point detection circuit 13A having the above configuration, even in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, when a load with which motor <NUM> can be normally driven is applied to motor <NUM>, the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM>.

On the other hand, according to cross point detection circuit 13A having the above configuration, in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, when a load greater than or equal to a load with which motor <NUM> can be normally driven is applied to motor <NUM>, similarly to cross point detection circuit <NUM> according to the first exemplary embodiment, the number of times of detection of the cross point to be detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM>. According to cross point detection circuit 13A having the above configuration, in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>, similarly to cross point detection circuit <NUM> according to the first exemplary embodiment, the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM> or <NUM>.

Therefore, in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM> and there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, cross point detection circuit 13A outputs a control signal to drive motor <NUM> when the load applied to motor <NUM> is a load with which motor <NUM> can be normally driven, and outputs a control signal not to drive motor <NUM> when there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM> and the load applied to motor <NUM> is a load greater than or equal to the load with which motor <NUM> can be normally driven.

In addition to a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>, even in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, motor drive device 10A having the above configuration outputs a control signal indicating that the motor <NUM> is to be driven when the load applied to motor <NUM> is small enough to normally drive motor <NUM>. On the other hand, in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, when the load applied to motor <NUM> is a load greater than or equal to a load with which drive motor <NUM> can be normally driven, motor drive device 10A outputs a control signal indicating that the motor <NUM> is not to be driven. As described above, according to motor drive device 10A having the above configuration, in a case where there is a possibility that motor <NUM> cannot be normally driven due to a phase loss in the three-phase alternating current serving as the power source, it is possible to output the control signal indicating that the motor <NUM> is not to be driven.

Hereinafter, a motor drive device according to a third exemplary embodiment configured such that a part of motor drive device <NUM> according to the first exemplary embodiment is changed will be described.

Hereinafter, in the motor drive device according to the third exemplary embodiment, components similar to the components of motor drive device <NUM> will be denoted by the same reference marks as those already described, detailed description thereof will be omitted, and differences from motor drive device <NUM> will be mainly described.

<FIG> is a block diagram illustrating a configuration of motor drive system 1B according to the third exemplary embodiment.

As illustrated in <FIG>, motor drive system 1B is configured such that motor drive device <NUM> of motor drive device <NUM> according to the first exemplary embodiment is changed to motor drive device 10B. As illustrated in <FIG>, motor drive device 10B is configured such that voltage detection circuit <NUM> and power calculation circuit <NUM> are added to motor drive device <NUM> and cross point detection circuit <NUM> is changed to cross point detection circuit 13B.

Voltage detection circuit <NUM> detects the voltage of the smoothed direct current smoothed by smoothing circuit <NUM>.

Power calculation circuit <NUM> calculates a power for driving motor <NUM> based on the current detected by current detection circuit <NUM> and the voltage detected by voltage detection circuit <NUM>.

In a case where the calculated power is smaller than a predetermined power value, power calculation circuit <NUM> outputs a first signal indicating that the calculated power is smaller than the predetermined power value. Here, even though there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, the predetermined power value is a maximum value of the power for driving motor <NUM> in a case where the load applied to motor <NUM> is a load with which motor <NUM> can be normally driven.

Similarly to cross point detection circuit <NUM> according to the first exemplary embodiment, cross point detection circuit 13B detects a cross point between the current detected by current detection circuit <NUM> and a predetermined current value (here, the predetermined current value is set to <NUM> [A].

Cross point detection circuit 13B outputs a drive signal indicating whether or not to drive motor <NUM> based on a detection result of the cross point. More specifically, cross point detection circuit 13B outputs (<NUM>) a control signal indicating that the motor <NUM> is not to be driven when the first signal is not output from power calculation circuit <NUM> in a case where the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM>, and outputs (<NUM>) a control signal indicating that the motor <NUM> is to be driven when the first signal is output from power calculation circuit <NUM> in a case where the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM> or <NUM> and in a case where the number of times of detection of the cross point detected in one cycle of the three-phase alternating current input to rectifier circuit <NUM> is <NUM>. That is, cross point detection circuit 13B outputs a control signal indicating that the motor <NUM> is not to be driven when the load applied to motor <NUM> is a load greater than or equal to a load with which motor <NUM> can be normally driven in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, and outputs a control signal indicating that the motor <NUM> is to be driven when the load applied to motor <NUM> is a load with which motor <NUM> can be normally driven in a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM> and in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>.

In addition to a case where there is no phase loss in the three-phase alternating current input to rectifier circuit <NUM>, even in a case where there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM>, when the load applied to motor <NUM> is small enough to normally drive motor <NUM>, motor drive device 10B having the above configuration suppresses the output of the control signal indicating that the motor <NUM> is not to be driven and instead outputs the control signal indicating that the motor <NUM> is to be driven. On the other hand, when there is a phase loss in the three-phase alternating current input to rectifier circuit <NUM> and the load applied to motor <NUM> is a load greater than or equal to a load with which motor <NUM> can be normally driven, motor drive device 10B outputs a control signal indicating that the motor <NUM> is not to be driven. As described above, according to motor drive device 10B having the above configuration, in a case where there is a possibility that motor <NUM> cannot be normally driven due to a phase loss in the three-phase alternating current serving as the power source, it is possible to output the control signal indicating that the motor <NUM> is not to be driven.

The motor drive device according to the present disclosure has been described above based on the first to third exemplary embodiments. Configurations in which various modifications conceived by those skilled in the art are applied to these exemplary embodiments, and configurations established by combining structural elements in different exemplary embodiments may also fall within the scope of one or more aspects.

Claim 1:
A motor drive device (<NUM>, 10A, 10B) configured to drive a motor (<NUM>) using a three-phase alternating current as a power source (<NUM>), the motor drive device (<NUM>, 10A, 10B) comprising:
a rectifier circuit (<NUM>) configured to rectify the three-phase alternating current to generate a rectified current;
a current detection circuit (<NUM>) configured to detect the rectified current;
a cross point detection circuit (<NUM>, 13A, 13B) configured to detect a cross point between the rectified current detected by the current detection circuit (<NUM>) and a predetermined current value, and to output a control signal indicating whether or not to drive the motor (<NUM>) ; and
a smoothing circuit (<NUM>) configured to smooth the rectified current and to generate a smoothed current; wherein
the cross point detection circuit (<NUM>, 13A, 13B) is configured to output the control signal indicating that the motor (<NUM>) is not to be driven in a case where a number of times of the detection of the cross point in one cycle of the three-phase alternating current is <NUM>,
the cross point detection circuit (<NUM>, 13A, 13B) is further configured to output the control signal indicating that the motor (<NUM>) is to be driven, in a case where a voltage of the smoothed current is equal to or higher than the minimum of a voltage of the rectified current and where the number of times of the detection of the cross point in one cycle of the three-phase alternating current is <NUM>, and
the cross point detection circuit (<NUM>, 13A, 13B) is further configured to output the control signal indicating that the motor (<NUM>) is to be driven, in a case where the voltage of the smoothed current is lower than the minimum of the voltage of the rectified current and where the number of times of the detection of the cross point in one cycle of the three-phase alternating current is <NUM>.