Motor control device, motor system and motor control method

Abstract

A method for energizing a motor having a rotor by turning on a portion of arms having different energization modes in all arms of an inverter, wherein PWM signals of each phase having periodic intervals are generated by duty ratios having the same value, the periodic intervals including a first interval in which the portion of arms are turned on in a first energization mode during an idling period of the rotor, a second interval in which the portion of arms are turned on in a second energization mode during the idling period, and a third interval in which all upper arms of all arms are turned on in a third energization mode during the idling period, and an offset current value of the first phase during the idling period is calculated by subtracting half of the sum of the first current value of the first phase flowing into the current detector in the first interval from the second current value of the first phase flowing into the current detector in the second interval.

Description

Technical Field

[0001] The present disclosure relates to a motor control device, a motor system and a motor control method. Background Art

[0002] Conventionally, a single-shunt current detection method is known in which a phase current of each phase for controlling a motor is detected using a single shunt resistor connected to a DC bus of an inverter circuit (for example, see Patent Document 1).

[0003] [Reference document]

[0004] [Patent document]

[0005] [Patent Document 1] (Japan) Patent Publication No. 2015-208071 Summary of the invention

[0006] <Technical issues to be solved>

[0007] When the motor is controlled by a 1-shunt current detection method, the current flowing into the 1-shunt current detector may be detected before the inverter rotates the rotor (before the motor is started). The current detected before the motor is started can be used, for example, for fault detection before the motor is started, or can be used to improve the accuracy of current detection and / or fault detection when the motor is started by the inverter and the inverter is rotating the rotor.

[0008] However, if the current flowing into the 1-way current sensor is detected while the rotor is idling before the inverter rotates the rotor, the rotation of the rotor may be hindered by the regenerative brake generated in the rotor during the idling period (i.e., during the idling period). If the rotation of the rotor during the idling period is hindered, unexpected behaviors such as motor deceleration and abnormal noise may occur.

[0009] An object of the present disclosure is to provide a motor control device, a motor system, and a motor control method that can reduce the obstruction of rotor idling by detecting the current flowing into a current detector.

[0010] <Technical solution>

[0011] A motor control device according to one embodiment of the present disclosure includes:

[0012] an inverter for energizing a motor having a rotor by turning on a portion of arms having different energization patterns among all arms;

[0013] A current detector connected to the DC side of the inverter;

[0014] a PWM signal generating unit that generates PWM signals of each phase having a first cycle interval by using a duty ratio having the same value, wherein the first cycle interval includes a first interval in which the part of the arms is turned on in a first energization mode during an idling period of the rotor, a second interval in which the part of the arms is turned on in a second energization mode during the idling period, and a third interval in which all upper arms or all lower arms of all the arms are turned on in a third energization mode during the idling period; and

[0015] The current detection unit calculates an offset current value of the first phase during the idling period by subtracting half of the sum of the first current value and the second current value from the first current value of the first phase flowing into the current detector in the first interval or the second current value of the first phase flowing into the current detector in the second interval.

[0016] <Beneficial Effects>

[0017] According to the present disclosure, the hindrance of rotor idling can be alleviated by detecting the current flowing into the current detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] [ Figure 1 ]A schematic diagram of a configuration example of a motor system according to embodiment 1 of the present disclosure.

[0019] [ Figure 2 ]Example diagram of the waveforms of multiple PWM signals, the waveform of the carrier of each cycle of these PWM signals, and the waveform of the phase voltage command of each phase.

[0020] [ Figure 3 ]A schematic diagram of an example of the switching state of each arm when power is supplied.

[0021] [ Figure 4 ]A schematic diagram of an example of the switching state of each arm when no power is supplied.

[0022] [ Figure 5 ] An example timing chart of the offset current of each phase flowing into the current detector by turning on some of the arms of all the arms of the inverter based on the PWM signal of each phase with a duty cycle of 50%.

[0023] [ Figure 6 ]When the inverter is rotating the rotor based on the PWM signals of each phase whose duty ratio is not 50%, Figure 5This is an exemplary timing diagram of the phase current of each phase flowing into the current detector when the same part of the arms is turned on.

[0024] [ Figure 7 ]A schematic diagram of a comparative example of a waveform of a PWM signal when the current value of the current flowing into the current detector before the inverter rotates the rotor is detected.

[0025] [ Figure 8 ] Schematic diagram of the situation where the lower arm is in the on state in the non-powered interval.

[0026] [ Fig. 9 ] Schematic diagram of the situation where the upper arm is in the on state in the non-powered interval.

[0027] [ Fig.10 ] Schematic diagram of the situation where both the upper and lower arms are in the disconnected (off) state in the non-powered range.

[0028] [ Fig.11 ]A schematic diagram of a first example of a waveform of a PWM signal when the current value of the current flowing into the current detector before the inverter rotates the rotor is detected.

[0029] [ Fig.12 ] An enlarged view of an example of the current waveform of the U-phase current flowing into the current detector when some of the arms of all the arms of the inverter are turned on based on the PWM signals of each phase with a duty ratio of 50%.

[0030] [ Fig.13 ]A schematic diagram of a second example of a waveform of a PWM signal when the current value of the current flowing into the current detector before the inverter rotates the rotor is detected.

[0031] [ Fig.14 ] Schematic diagram of the switching state of the negative U-phase current "-Iu" flowing into the current detector.

[0032] [ Fig.15 ] Schematic diagram of the switching state of the positive U-phase current “+Iu” flowing into the current detector.

[0033] [ Fig.16 ] is a waveform diagram showing an example of the calculation processing of the U-phase offset current value within 10 cycles of the PWM signal when the rotor is idling.

[0034] [ Fig.17 ] Fig.16 An enlarged view of a portion enclosed by a dashed box is shown.

[0035] [ Fig.18 ] is a waveform diagram showing an example of calculation processing of the U-phase offset current value.

[0036] [ Fig.19 ] is a waveform diagram showing an example of calculation processing of the W-phase offset current value. DETAILED DESCRIPTION

[0037] The motor control device, the motor system, and the motor control method according to the embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0038] Figure 1 It is a schematic diagram of a configuration example of a motor system 1 - 1 according to Embodiment 1 of the present disclosure. Figure 1 The motor system 1-1 shown is used to control the rotation of the motor 4. Examples of devices to which the motor system 1-1 can be installed include, but are not limited to, copy machines, personal computers, refrigerators, pumps, etc. The motor system 1-1 includes at least the motor 4 and a motor control device 100-1.

[0039] The motor 4 is a permanent magnet synchronous motor having a plurality of coils. The motor 4, for example, has a three-phase coil including a U-phase coil, a V-phase coil, and a W-phase coil. As a specific example of the motor 4, a three-phase brushless DC motor (electric motor) and the like can be cited. The motor 4 has a rotor having at least one permanent magnet and a stator arranged around the axis of the rotor. The motor 4 is a sensorless motor that does not use a position sensor for detecting the angular position (magnetic pole position) of the magnet of the rotor. The motor 4 is, for example, a fan motor that rotates a fan for blowing air.

[0040] The motor control device 100-1 drives the motor via an inverter that converts direct current into a three-phase alternating current by controlling the on / off (on / off) of a plurality of switching elements (also called switching elements) connected in a three-phase bridge based on an energization pattern including a three-phase PWM signal. The motor control device 100-1 includes an inverter 23, a current detection unit 27, a current detection timing adjustment unit 34, a drive circuit 33, an energization pattern generation unit 35, a carrier generation unit 37, and a clock signal generation unit 36.

[0041] The inverter 23 is a circuit that converts the DC supplied from the DC power supply 21 into a three-phase AC by switching a plurality of switching elements, and causes the three-phase AC driving current to flow into the motor 4, thereby rotating the rotor of the motor 4. The inverter 23 drives the motor 4 according to a plurality of energization patterns generated by the energization pattern generation unit 35 (specifically, a three-phase PWM signal generated by the PWM signal generation unit 32 in the energization pattern generation unit 35). PWM refers to Pulse Width Modulation.

[0042] The inverter 23 has a plurality of arms Up, Vp, Wp, Un, Vn, and Wn connected in a three-phase bridge. The upper arms Up, Vp, and Wp are high-side switching elements connected to the positive side of the DC power supply 21 via the positive bus (positive bus) 22a. The lower arms Un, Vn, and Wn are low-side switching elements connected to the negative side (specifically, the ground side) of the DC power supply 21. The plurality of arms Up, Vp, Wp, Un, Vn, and Wn are turned on or off according to corresponding drive signals among the plurality of drive signals supplied from the drive circuit 33 based on the PWM signal included in the above-mentioned power-on mode. Hereinafter, when there is no need to distinguish the plurality of arms Up, Vp, Wp, Un, Vn, and Wn in particular, they are sometimes referred to simply as arms.

[0043] The connection point of the U-phase upper arm Up and the U-phase lower arm Un is connected to one end of the U-phase coil of the motor 4. The connection point of the V-phase upper arm Vp and the V-phase lower arm Vn is connected to one end of the V-phase coil of the motor 4. The connection point of the W-phase upper arm Wp and the W-phase lower arm Wn is connected to one end of the W-phase coil of the motor 4. The other ends of the U-phase coil, the V-phase coil, and the W-phase coil are connected to each other.

[0044] Specific examples of the arm include N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor), IGBT (Insulated Gate Bipolar Transistor), etc. However, the arm is not limited to these.

[0045] The current detector 24 is connected to the DC side of the inverter 23 , and outputs a detection signal Sd corresponding to the current value of the current flowing into the DC side of the inverter 23 . Figure 1 The current detector 24 shown generates a detection signal Sd corresponding to the current value of the current flowing through the negative bus (negative bus) 22b. The current detector 24 is, for example, a current detection element arranged on the negative bus 22b, specifically, a shunt resistor inserted into the negative bus 22b. The current detection element such as the shunt resistor generates a voltage signal corresponding to the current value of the current flowing through itself, and uses it as the detection signal Sd.

[0046] The current detection unit 27 acquires the detection signal Sd based on the multiple energization patterns (specifically, the 3-phase PWM signals) generated by the energization pattern generation unit 35, thereby detecting the phase currents Iu, Iv, and Iw of the U, V, and W phases flowing into the motor 4. In detail, the current detection unit 27 acquires the detection signal Sd at an acquisition timing (timing) synchronized with the multiple energization patterns (specifically, the 3-phase PWM signals), thereby detecting the phase currents Iu, Iv, and Iw of the U, V, and W phases flowing into the motor 4. The acquisition timing of the detection signal Sd is set by the current detection timing adjustment unit 34.

[0047] For example, the current detection unit 27 inputs the detection signal Sd of the analog voltage generated by the current detector 24 to an AD (Analog to Digital) converter at the acquisition timing set by the current detection timing adjustment unit 34. The AD converter is provided in the current detection unit 27. Thereafter, the current detection unit 27 performs AD conversion on the input analog detection signal Sd to convert it into a digital detection signal Sd, and performs digital processing on the digital detection signal Sd after the AD conversion, thereby detecting the phase currents Iu, Iv, and Iw of the U, V, and W phases of the motor 4. The detection values ​​of the phase currents Iu, Iv, and Iw of the phases detected by the current detection unit 27 are supplied to the energization pattern generation unit 35.

[0048] The clock signal generating unit 36 ​​is a circuit that generates a clock signal of a predetermined frequency by a built-in oscillation circuit and outputs the generated clock signal to the carrier generating unit 37. It should be noted that the clock signal generating unit 36 ​​starts to operate (operate / work) when the power of the motor control device 100-1 is turned on (put on), for example.

[0049] The carrier wave generating unit 37 generates a carrier wave C based on the clock signal generated by the clock signal generating unit 36. The carrier wave C is a carrier wave signal whose level increases and decreases periodically.

[0050] The power-on pattern generation unit 35 generates a pattern for energizing the inverter 23 (power-on pattern of the inverter 23). The power-on pattern of the inverter 23 may also be referred to as a pattern for energizing the motor 4 (power-on pattern of the motor 4). The power-on pattern of the inverter 23 includes a three-phase PWM signal for energizing the inverter 23. The power-on pattern generation unit 35 includes a PWM signal generation unit 32, which generates a three-phase PWM signal for energizing the inverter 23 based on the detection values ​​of the phase currents Iu, Iv, and Iw of the motor 4 detected by the current detection unit 27, so as to rotate the motor 4.

[0051] When generating the energizing pattern of the inverter 23 by vector control, the energizing pattern generating unit 35 further includes the vector control unit 30. In this embodiment, the energizing pattern of the inverter is generated by vector control, but the present invention is not limited thereto, and the phase voltage of each phase may be obtained by VF control or the like.

[0052] When the rotation speed command ωref of the motor 4 is given from the outside, the vector control unit 30 generates a torque current command Iqref and an excitation current command Idref based on the difference between the measured value or estimated value of the rotation speed of the motor 4 and the rotation speed command ωref. The vector control unit 30 calculates the torque current Iq and the excitation current Id based on the phase currents Iu, Iv, Iw of the U, V, and W phases of the motor 4 by vector control calculation using the rotor position θ. The vector control unit 30 generates the voltage command Vq by, for example, performing a PI control calculation on the difference between the torque current command Iqref and the torque current Iq. The vector control unit 30 generates the voltage command Vd by, for example, performing a PI control calculation on the difference between the excitation current command Idref and the excitation current Id. The vector control unit 30 converts the voltage commands Vq and Vd into phase voltage commands Vu*, Vv*, and Vw* of the U, V, and W phases using the above-mentioned rotor position θ. The rotor position θ indicates the magnetic pole position of the rotor of the motor 4.

[0053] The PWM signal generating unit 32 generates a conduction pattern including a three-phase PWM signal by comparing the phase voltage commands Vu*, Vv*, and Vw* generated by the vector control unit 30 with the level of the carrier C generated by the carrier generating unit 37. The PWM signal generating unit 32 also generates a PWM signal for driving the lower arm for inverting the three-phase PWM signal for driving the upper arm, and outputs the conduction pattern including the generated PWM signal to the drive circuit 33 after adding a dead time as needed.

[0054] The drive circuit 33 outputs a drive signal for switching the six arms Up, Vp, Wp, Un, Vn, and Wn included in the inverter 23 according to the energization pattern including the PWM signal given. As a result, a three-phase AC drive current is supplied to the motor 4, and the rotor of the motor 4 can rotate.

[0055] The current detection timing adjustment unit 34 determines the acquisition timing for the current detection unit 27 to detect the phase current of any one of the three phases within one cycle of the carrier C, based on the carrier C supplied from the carrier generation unit 37 and the energization pattern including the PWM signal generated by the PWM signal generation unit 32 .

[0056] The current detection unit 27 detects the phase currents Iu, Iv, and Iw by acquiring the detection signal Sd at a plurality of acquisition timings determined by the current detection timing adjustment unit 34. The current detection unit 27 detects the phase currents Iu, Iv, and Iw in a manner in which a plurality of phase currents are detected from a single current detector 24 (i.e., a so-called single-shunt current detection method).

[0057] In addition, as a method for estimating the magnetic pole position (initial position) of the rotor when the sensorless permanent magnet synchronous motor is in a stopped state, there is a method called inductive sensing. Inductive sensing refers to a method of detecting the magnetic pole position of the rotor magnet of the permanent magnet synchronous motor using the rotor position dependence of inductance. This position detection method does not use the induced voltage of the motor, so the magnetic pole position of the rotor magnet can be detected even when the rotor of the motor is stopped or in an extremely low speed state. The state of the rotor in an extremely low speed refers to a state in which the rotor rotates at a low speed at which the motor control device is substantially unable to detect the induced voltage. In this specification, for the sake of convenience of description, "the state in which the rotor is stopped or in an extremely low speed" is referred to as "the stopped state of the rotor".

[0058] The motor control device 100-1 of the first embodiment includes an initial position estimation unit 38 that estimates the magnetic pole position of the rotor of the motor in a stopped state, that is, the initial position θs, by inductive detection. The power-on pattern generation unit 35 uses the initial position θs estimated by the initial position estimation unit 38 to output the power-on pattern including the PWM signal for rotating the rotor of the motor 4 to the drive circuit 33. The vector control unit 30 uses the initial position θs estimated by the initial position estimation unit 38 as the initial value of the rotor position θ, thereby converting the voltage instructions Vq and Vd into phase voltage instructions Vu*, Vv*, and Vw*. It should be noted that in the present disclosure, as an example, the initial position θs is a value having a width of 30 degrees. In such a case, a predetermined value determined based on the initial position θs is used to control the motor 4.

[0059] Figure 2 The diagram exemplifies waveforms of a plurality of PWM signals U, V, and W, a waveform of a carrier C in each cycle of these PWM signals, and waveforms of phase voltage commands Vu*, Vv*, and Vw* of each phase.

[0060] The PWM signal generating unit 32 generates a plurality of PWM signals U, V, W according to the magnitude relationship between the phase voltage commands Vu*, Vv*, Vw* of each phase and the level of the carrier C.

[0061] The PWM signal U is a PWM signal for driving the two switching elements constituting the upper and lower arms of the U phase. In this example, when the PWM signal U is at a low level, the switching element of the lower arm of the U phase becomes on (the switching element of the upper arm of the U phase becomes off), and when the PWM signal U is at a high level, the switching element of the lower arm of the U phase becomes off (the switching element of the upper arm of the U phase becomes on). The two switching elements constituting the upper and lower arms of the U phase complementarily perform on / off operations in response to changes in the level of the PWM signal U.

[0062] The PWM signal V is a PWM signal for driving the two switching elements constituting the upper and lower arms of the V phase. In this example, when the PWM signal V is at a low level, the switching element of the lower arm of the V phase becomes on (the switching element of the upper arm of the V phase becomes off), and when the PWM signal V is at a high level, the switching element of the lower arm of the V phase becomes off (the switching element of the upper arm of the V phase becomes on). The two switching elements constituting the upper and lower arms of the V phase complementarily perform on / off operations in response to changes in the level of the PWM signal V.

[0063] The PWM signal W is a PWM signal for driving the two switching elements constituting the upper and lower arms of the W phase. In this example, when the PWM signal W is at a low level, the switching element of the lower arm of the W phase becomes on (the switching element of the upper arm of the W phase becomes off), and when the PWM signal W is at a high level, the switching element of the lower arm of the W phase becomes off (the switching element of the upper arm of the W phase becomes on). The two switching elements constituting the upper and lower arms of the W phase complementarily perform on / off operations in response to changes in the level of the PWM signal W.

[0064] It should be noted that Figure 2 In the figure, the dead time for preventing the upper and lower arms from shorting out is omitted. Figure 2 The following definition is also made in that when the PWM signal is at a high level, the upper arm of the phase corresponding to the PWM signal is turned on, and when the PWM signal is at a low level, the lower arm of the phase corresponding to the PWM signal is turned on. However, considering the circuit structure, etc., the relationship between the logic level of the PWM signal and the on / off of each arm can also be defined in the opposite way.

[0065] One cycle Tpwm of each of the plurality of PWM signals U, V, and W corresponds to the cycle (the inverse of the carrier frequency) of the carrier C. The change points (t1 to t6) indicate the timings (times) at which the logic levels of the PWM signals transition (change).

[0066] like Figure 2As shown, the PWM signal generating unit 32 can use a carrier C shared by each phase to generate the PWM signal of each phase. Since the left-right symmetrical triangle wave centered on the phase tb is used as the carrier C, the circuit structure for generating the waveform of the PWM signal of each phase can be simplified. The counter of the carrier C counts down (down count) until the phase ta, counts up (up count) from the phase ta to the phase tb, and counts down from the phase tb. The counting period and the countdown period are repeated in this way. It should be noted that the PWM signal generating unit 32 can also use multiple carriers C corresponding to each phase to generate the PWM signal of each phase, and other well-known methods can also be used to generate the PWM signal of each phase.

[0067] Figure 2 The case where the first current detection timing Tm1 is set in the energization period T21 and the second current detection timing Tm2 is set in the energization period T22 is exemplified. Note that the energization periods for setting the first current detection timing Tm1 and the second current detection timing Tm2 are not limited to these periods.

[0068] When the inverter 23 is outputting a PWM-modulated three-phase AC, the current detection unit 27 can detect the current of a specific (predetermined) phase according to the power-on pattern corresponding to the upper arms Up, Vp, and Wp. Alternatively, when the inverter 23 is outputting a PWM-modulated three-phase AC, the current detection unit 27 can detect the current of a specific phase according to the power-on pattern corresponding to the lower arms Un, Vn, and Wn.

[0069] For example, Figure 2 As shown, during the power-on period T21, the voltage value of the voltage generated at both ends of the current detector 24 corresponds to the current value of the positive U-phase current "+Iu" flowing out of the U-phase terminal of the motor 4. The power-on period T21 is the time (period) from t4 to t5. The power-on period T21 is equivalent to the period when the lower arm Un and the upper arms Vp and Wp are turned on and the remaining three arms are cut off. To this end, the current detection unit 27 obtains the detection signal Sd at the first current detection timing Tm1 during the power-on period T21, and can detect the current value of the positive U-phase current "+Iu" flowing out of the U-phase terminal of the motor 4.

[0070] The current detection timing adjustment unit 34 sets the first current detection timing Tm1 when a predetermined delay time td has passed since the time when one phase of the PWM signal changes to a logic level different from the other two phases (for example, the time when the PWM signal of the U phase changes from a high level that is the same as the V phase and the W phase to a low level that is different from the V phase and the W phase: t4). At this time, the current detection timing adjustment unit 34 sets the first current detection timing Tm1 within the power-on period T21.

[0071] In addition, for example, Figure 2 As shown, during the power-on period T22, the voltage value of the voltage generated at both ends of the current detector 24 corresponds to the current value of the negative W-phase current "-Iw" flowing from the W-phase terminal of the motor 4. The power-on period T22 is the time (period) from t5 to t6. The power-on period T22 corresponds to the period when the lower arm Un, Vn and the upper arm Wp are turned on and the remaining three arms are turned off. To this end, the current detection unit 27 can detect the current value of the negative W-phase current "-Iw" flowing from the W-phase terminal of the motor 4 by acquiring the detection signal Sd at the second current detection timing Tm2 during the power-on period T22.

[0072] The current detection timing adjustment unit 34 sets the second current detection timing Tm2 when a predetermined delay time td has passed since the time when one phase in the PWM signal changes to a logic level different from the other two phases (for example, the time when the PWM signal of the V phase changes from the high level same as the W phase to the low level same as the U phase, resulting in the W phase changing to a logic level different from the U phase and the V phase: t5). At this time, the current detection timing adjustment unit 34 sets the second current detection timing Tm2 within the power-on period T22.

[0073] Similarly, the current detection unit 27 can also detect the current values ​​of other phase currents.

[0074] As described above, if the phase currents of two phases among the phase currents Iu, Iv, and Iw are detected and stored in sequence according to the energization pattern of the PWM signal including the three phases, the currents of the three phases can be detected in a time division manner. Since the sum of the phase currents of the three phases is zero (iu+iv+iw=0), if the current detection unit 27 can detect the phase currents of two phases among the three phases, the phase current of the remaining one phase can also be detected (calculated).

[0075] Figure 3 This is a diagram showing an example of the switch state of each arm when power is supplied. Figure 4 This is a diagram showing an example of the switch state of each arm when no power is supplied. Figure 3 As shown in FIG. 1 , during the energization period in which the upper arm Up and the lower arms Vn and Wn are turned on and the remaining three arms are turned off, the current detection unit 27 can detect the current value of the negative U-phase current "-Iu" flowing from the U-phase terminal of the motor 4. Figure 4As shown in FIG. 1 , when all upper arms Up, Vp, and Wp are turned on and all lower arms Un, Vn, and Wn are turned off, current does not flow into the current detector 24, so the current detection unit 27 cannot detect the phase current of each phase. When all upper arms Up, Vp, and Wp are turned off and all lower arms Un, Vn, and Wn are turned on, current does not flow into the current detector 24, so the current detection unit 27 cannot detect the phase current of each phase.

[0076] As mentioned above, in the 1-shunt current detection method, if the energization interval (energization period) is not set, the phase current of each phase cannot be detected. In addition, in the 1-shunt current detection method, the phase current that can be detected in one energization period is only one phase, so it is necessary to set at least two energization periods in one cycle of the PWM signal (see Figure 2 ), and the phase currents of the three phases are distinguished and detected according to the formula (iu+iv+iw=0). However, if a power-on period is set in order to distinguish and detect the phase currents of each phase, the current flowing into the current detector 24 will be amplified. Therefore, when the current flowing into the current detector 24 is zero, the current detection unit 27 cannot separately measure the detection error contained in the detection value of the phase current of each phase.

[0077] Therefore, when the motor is in a stopped state, the current flowing into each phase of the current detector 24 by turning on a part of all the arms of the inverter 23 based on the PWM signals of each phase having the same duty ratio may be defined as an offset current. In this case, the current detection unit 27 detects the current value of the offset current flowing into each phase of the current detector 24 by turning on a part of all the arms of the inverter 23 based on the PWM signals of each phase having the same duty ratio as the offset current value (detection error).

[0078] Figure 5 This is a timing chart illustrating an example of an offset current flowing into each phase of the current detector 24 when some of the arms of all the arms of the inverter 23 are turned on according to the PWM signals of each phase when the duty ratio is 50%. Figure 6 When the inverter 23 is rotating the rotor according to the PWM signals of each phase whose duty ratio is not 50%, Figure 5 This is a timing chart illustrating an example of a phase current of each phase flowing into the current detector 24 when the same part of the arms is turned on.

[0079] Figure 5In the embodiment, before the inverter 23 rotates the rotor (before the motor 4 is started), the current detection unit 27 detects the current value of each of the three-phase offset currents by performing current detection at least twice in each cycle of the PWM signal. The current detection unit 27 stores each detected current value in the memory as the three-phase offset current value. Figure 5 The following example is shown, that is, the current detection unit 27 detects the offset current value of each of the positive U-phase current "Iu" and the negative W-phase current "-Iw", and detects (calculates) the offset current value of the remaining V-phase current based on these detection results, and then stores the detected offset current values ​​of the three phases in the memory. After the offset current values ​​of the three phases are stored in the memory, the motor 4 is started by the inverter 23, and the inverter 23 rotates the rotor.

[0080] Figure 6 When the inverter 23 is rotating the rotor according to the PWM signals of each phase whose duty ratio is not 50%, the current detection unit 27 uses the same current detection unit as the current detection unit in each cycle of the PWM signal. Figure 5 The current detection is performed at least twice in the same power-on mode, thereby detecting the current value of each of the three-phase phase currents. In each cycle of the PWM signal, the current detection unit 27 subtracts the offset current value of the three phases pre-stored in the memory from the current value of each of the three-phase phase currents detected in accordance with each cycle of the PWM signal, thereby calculating the current detection value of each of the three-phase phase currents Iu, Iv, and Iw. Accordingly, the detection error can be removed from the current detection value of each of the three-phase phase currents Iu, Iv, and Iw. Based on the current detection values ​​of each of the three-phase phase currents Iu, Iv, and Iw from which the detection error has been removed, the PWM signal generation unit 32 generates a three-phase PWM signal when the inverter 23 is rotating the rotor, thereby enabling the rotation of the motor 4 to be controlled with high precision through the inverter 23.

[0081] In addition, even when the inverter 23 does not rotate the rotor by three-phase AC current, the rotor may idle due to interference such as wind. In particular, the rotor that rotates a rotating body such as a fan with a small friction resistance is more likely to idle. Before the inverter 23 rotates the rotor by three-phase AC current, when the rotor is idling, if the current flowing into the current detector 24 is detected at this time, the regenerative braking generated in the rotor during the idling period will hinder the rotation of the rotor. When the rotation of the rotor during the idling period is hindered, unexpected actions (behaviors) such as deceleration of the motor 4 and abnormal noise may occur.

[0082] Figure 7A comparative example of the waveform of the PWM signal when the current value of the current flowing into the current detector before the inverter rotates the rotor is shown, in which the duty ratio of the PWM signal of each phase is 50%. From the waveform of the PWM signal of each phase, it can be seen that there is a period when the regenerative current flows (regeneration interval) and a period when the regenerative current does not flow (non-regeneration interval). Figure 7 The de-energized section shown corresponds to the regeneration section. In the regeneration section (de-energized section), all upper arms or all lower arms are in the on state.

[0083] Figure 8 is a schematic diagram showing the situation where the lower arm is in the on state in the non-powered interval, which shows Figure 7 The switching state within the non-powered interval on both sides. Fig. 9 is a schematic diagram showing the situation where the upper arm is in the on state in the non-powered interval, which shows the Figure 7 The switch state in the middle non-powered interval sandwiched by the non-powered intervals on both sides. When the rotor of motor 4 is idling due to external forces such as wind, the idling of the rotor will cause induced voltages to be generated in the coils of each phase of motor 4. Through these induced voltages, Figure 8 and Fig. 9 As shown, in Figure 7 In the de-energized interval shown, a regenerative current flows from the motor 4 to the inverter 23, thereby regeneratively braking the rotor during the idling period. The rotation of the rotor during the idling period is hindered by the regenerative braking, and unexpected behaviors such as motor deceleration and abnormal noise may occur.

[0084] <Current detection method 1 when the rotor is idling>

[0085] In the "rotor idling current detection method 1" of the present disclosure, in order to prevent the regenerative current from flowing in the non-energized interval, as shown in FIG. Fig.10 As shown in FIG. 1 , the PWM signal generating unit 32 generates PWM signals of each phase for setting all arms of the inverter 23 to the disconnected state. Thus, even if the rotor is idling, since all arms of the inverter 23 are in the disconnected state in the non-energized section, theoretically no regenerative current will flow from the motor 4 to the inverter 23. Therefore, the obstruction to the rotation of the rotor caused by the regenerative braking generated in the rotor during the idling period can be reduced, and for example, the possibility of unexpected behavior such as deceleration of the motor 4 and abnormal noise can be reduced.

[0086] Fig.11It is a schematic diagram of a first example of the waveform of a PWM signal when the current value of the current flowing into the current detector before the inverter rotates the rotor is detected. The inverter 23 can energize the motor 4 having a rotor by turning on a part of the arms in which each energization mode is different among all the arms. The PWM signal generating unit 32 generates PWM signals of each phase including "a first period in which all arms are cut off during the idling period of the rotor", "a second period in which a part of the arms are turned on in the first energization mode during the idling period of the rotor", and "a third period in which a part of the arms are turned on in the second energization mode during the idling period of the rotor" in one cycle. Based on this, the following can be obtained: Fig.11 The switch status of each arm is shown.

[0087] exist Fig.11 In the example shown, the non-power-conducting interval T1 in which all arms are in the cut-off state is an example of the first period, the first half interval T2 of the current detection interval in which a part of the arms are in the conductive state in the first power-conducting mode is an example of the second period, and the second half interval T3 of the current detection interval in which a part of the arms are in the conductive state in the second power-conducting mode is an example of the third period.

[0088] In the first half section T2 of the current detection interval (an example of the second period), since the lower arm Un and the upper arms Vp and Wp are turned on in the first energization mode, the positive U-phase current "+Iu" flowing out from the U-phase terminal of the motor 4 can flow into the current detector 24. In the second half section T3 of the current detection interval (an example of the third period), since the lower arms Un, Vn and the upper arm Wp are turned on in the second energization mode, the negative W-phase current "-Iw" flowing in from the W-phase terminal of the motor 4 can flow into the current detector 24. Accordingly, the current detection unit 27 can detect the first reference current (the positive U-phase current "+Iu" in this example) flowing into the current detector 24 in the first half section T2 and the second reference current (the negative W-phase current "-Iw" in this example) flowing into the current detector 24 in the second half section T3.

[0089] As described above, according to the current detection method 1, since all arms are in the disconnected state in the non-energized section T1, the generation of unnecessary torque that can generate regenerative braking can be suppressed. For this reason, before the inverter 23 rotates the rotor by the three-phase AC current, when the rotor is idling, even if the current detection unit 27 detects the current flowing into the current detector 24 in the current detection section, since there is the non-energized section T1 in which all arms are in the disconnected state, the idling of the rotor is hardly hindered.

[0090] exist Fig.11In the example shown, the current detection interval, which is an example of the total period of the second period and the third period, is set to be shorter than the non-energized interval, which is an example of the first period. In the non-energized interval, since the regenerative braking state is cut off, the generation of unnecessary torque that can generate regenerative braking can be suppressed. On the other hand, since the current detection interval is shorter than the non-energized interval, only a small current can flow during the energized time (period) in the current detection interval. For this reason, before the inverter 23 rotates the rotor by the three-phase AC current, when the rotor is idling, even if the current detection unit 27 detects the current flowing into the current detector 24 in the current detection interval at this time, the obstruction of the rotor rotation during the idling period can be reduced. As a result, for example, the occurrence of unexpected behaviors such as deceleration of the motor 4 and abnormal noise can be suppressed.

[0091] For example, the current detection unit 27 can correct the phase current of the first phase flowing into the current detector 24 when the inverter 23 is rotating the rotor based on the first reference current of the first phase detected in the second period. Similarly, the current detection unit 27 can also correct the phase current of the second phase flowing into the current detector 24 when the inverter 23 is rotating the rotor based on the second reference current of the second phase detected in the second period. For example, the first phase is the U phase and the second phase is the W phase, but other combinations are also possible. Since the current does not flow into the current detector 24 in the first period of one cycle, the first reference current flowing into the current detector 24 in the second period and the second reference current flowing into the current detector 24 in the third period can be regarded as two-phase reference currents such as the above-mentioned offset current.

[0092] The current detection unit 27 can detect (calculate) the third reference current of the third phase flowing into the current detector 24 during the idling period of the rotor, for example, based on the first reference current of the first phase detected during the second period and the second reference current of the second phase detected during the third period, and using the formula that the sum of the phase currents of the three phases is zero. The third reference current of the third phase can also be regarded as a reference current of one phase like the above-mentioned offset current. The third phase is, for example, the V phase. The current detection unit 27 can correct the phase current of the third phase flowing into the current detector 24 when the inverter 23 is rotating the rotor based on the detected (calculated) third reference current of the third phase.

[0093] For example, the value of the first reference current of the first phase is used as the first reference current value, the value of the second reference current of the second phase is used as the second reference current value, and the value of the third reference current of the third phase is used as the third reference current value. The current detection unit 27 detects the first reference current value in the second period, detects the second reference current value in the third period, and detects (calculates) the remaining third reference current value based on these detection results, and then stores the detected reference current values ​​of the three phases in the memory. After the reference current values ​​of the three phases are stored in the memory, the motor 4 is started by the inverter 23, and the inverter 23 rotates the rotor.

[0094] When the inverter 23 is rotating the rotor, the current detection unit 27 generates a current corresponding to the current of the inverter 23 in each cycle of the PWM signal. Fig.11 The current detection is performed at least twice in the same energization mode, thereby detecting the current value of each phase current of the three phases. The current detection unit 27 subtracts the reference current value of the three phases stored in advance in the memory from the current value of each phase current of the three phases detected according to each cycle of the PWM signal, thereby calculating the current detection value of each phase current Iu, Iv, and Iw of the three phases. According to this, the current detection unit 27 can correct the phase current of each phase flowing into the current detector 24 when the inverter 23 is rotating the rotor according to the reference current of each phase, so that the detection error can be removed from the current detection value of each phase current Iu, Iv, and Iw of the three phases. The PWM signal generation unit 32 uses the current detection value of each phase current Iu, Iv, and Iw of the three phases after correction with the detection error removed to generate the PWM signal of the three phases when the inverter 23 is rotating the rotor, thereby controlling the rotation of the motor 4 with high accuracy through the inverter 23.

[0095] It should be noted that, as a method other than the above, for example, it is also possible to use only the general port function instead of the PWM function to output an on / off signal from the port to generate Fig.10 status.

[0096] <Current detection method 2 when the rotor is idling>

[0097] Next, the “current detection method 2 when the rotor is idling” of the present disclosure will be described.

[0098] Fig.12 This is an enlarged diagram showing an example of a current waveform of the U-phase current flowing into the current detector 24 when some of all the arms of the inverter are turned on by PWM signals of each phase having a duty ratio of 50%. Fig.12 In the figure, the upper waveform shows the waveform when the rotor is stopped, and the lower waveform shows the waveform when the rotor is idling. Fig.12The waveforms of about 16 cycles of the PWM signal are illustrated. The two waveforms are shifted up and down (misaligned) with almost no change, and this shift is caused by the induced voltage generated in the coil of each phase of the motor 4 due to the idling of the rotor.

[0099] Fig.13 It is a schematic diagram of a second example of the waveform of the PWM signal when the current value of the current flowing into the current detector 24 before the inverter rotates the rotor is detected. The inverter 23 energizes the motor 4 having the rotor by turning on a part of the arms in which each energization mode is different among all the arms. The PWM signal generating unit 32 generates PWM signals of each phase having a first period interval by using a duty ratio of the same value, and the first period interval includes a first interval in which a part of the arms are turned on in the first energization mode during the idling period of the rotor, a second interval in which a part of the arms are turned on in the second energization mode during the idling period of the rotor, and a third interval in which all the upper arms or all the lower arms are turned on in the third energization mode during the idling period of the rotor. Based on this, it can be obtained Fig.13 The switch status of each arm as shown.

[0100] exist Fig.13 In the example shown, the first current detection interval P1 (including the period of the first detection timing) in which a part of the arms is turned on in the first power-on mode is an example of the first interval, and the second current detection interval P2 (including the period of the second detection timing) in which a part of the arms is turned on in the second power-on mode is an example of the second interval. The non-power-on interval P3 in which all the upper arms are turned on and all the lower arms are turned off is an example of the third interval. In this example, the third interval is between the first interval and the second interval.

[0101] In the first current detection interval P1 (an example of the first interval), the upper arm Up and the lower arms Vn and Wn are turned on in the first energization mode, so the negative U-phase current "-Iu" flowing from the U-phase terminal of the motor 4 can flow into the current detector 24 (see Fig.14 In the second current detection interval P2 (an example of the second interval), the lower arm Un and the upper arms Vp and Wp are turned on in the second energization mode, so the positive U-phase current "+Iu" flowing from the U-phase terminal of the motor 4 can flow into the current detector 24 (see Fig.15 ). Accordingly, the current detection unit 27 can detect the first current value of the first phase flowing into the current detector 24 in the first interval and the second current value of the first phase flowing into the current detector 24 in the second interval. In this example, the first current value is the current value of the negative U-phase current "-Iu (=Iv+Iw)", and the second current value is the current value of the positive U-phase current "+Iu".

[0102] In the current detection method 2, the current detection unit 27 uses the fact that the phase current of the first phase detected in one cycle of the PWM signal is a pair, and detects the difference between half of the sum of the first current value of the first phase and the second current value of the first phase and zero as the influence of the induced voltage. Then, the current detection unit 27 subtracts the detected influence of the induced voltage from the first current value or the second current value detected at the first or second detection timing, thereby calculating the offset current value of the first phase. In addition, for the second phase or the third phase other than the first phase, the current detection unit 27 can calculate the offset current value in the same manner even during the idling period of the rotor by adopting the same method.

[0103] Fig.16 This is a waveform diagram showing an example of calculation processing of the U-phase offset current value within 10 cycles (for example, 400 μs) of the PWM signal when the rotor is idling. Fig.17 yes Fig.16 The enlarged view of the portion surrounded by the dotted line frame is a waveform diagram showing an example of calculation processing of the U-phase offset current value within one cycle (eg, 40 μs) of the PWM signal when the rotor is idling. The U-phase is an example of the first phase.

[0104] The current detection unit 27 can derive the influence component e of the induced voltage by calculating half of the sum of the first current value (-Iu+e) of the U phase flowing into the current detector 24 during the first detection in the first interval and the second current value (Iu+e) of the U phase flowing into the current detector 24 during the second detection in the second interval. Fig.16 and Fig.17 In the illustrated example, the current detection unit 27 can calculate the U-phase offset current value Iu by subtracting the influence component e from the second current value (Iu+e) of the U-phase detected for the second time.

[0105] As described above, according to the current detection method 2, the U-phase offset current value can be calculated within the time (period) of one cycle of the PWM signal. In other words, the U-phase offset current value can be calculated in a short time (quickly) even during the idling period of the rotor, so the idling of the rotor is less likely to be hindered. As a result, for example, the occurrence of unexpected behaviors such as deceleration of the motor 4 and abnormal noise can be suppressed.

[0106] Fig.18 : is a waveform diagram showing an example of the calculation process of the U-phase offset current value. Fig.19 : is a waveform diagram showing an example of calculation processing of the W-phase offset current value. Fig.19 As shown, the W-phase offset current value (or V-phase offset current value) is calculated in the same manner as the U-phase offset current value.

[0107] Fig.18The example shows a case where the PWM signal generating unit 32 generates PWM signals for each phase having a first period interval with a duty ratio of 50%. The PWM signal generating unit 32 generates PWM signals for each phase having a first period interval, and the first period interval includes a first interval Q1 for causing a part of the arms to conduct in a first energization mode during the idling period of the rotor, a second interval Q2 for causing a part of the arms to conduct in a second energization mode during the idling period of the rotor, and a third interval Q3 for causing all upper arms or all lower arms to conduct in a third energization mode during the idling period of the rotor. Fig.18 In the example shown, the first cycle section includes the first section Q1 including the first detection timing, the second section Q2 including the second detection timing, and the third section Q3 in which all upper arms are turned on. The current detection unit 27 subtracts half of the sum of the first current value and the second current value from the first current value of the first phase flowing into the current detector 24 in the first section Q1 or the second current value of the first phase flowing into the current detector 24 in the second section Q2. In this example, the current detection unit 27 can calculate the offset current value of the first phase by performing the operation of subtracting from the second current value. Fig.18 The case where the first phase is the U phase is illustrated.

[0108] Fig.19 The example shows a case where the PWM signal generating unit 32 generates PWM signals for each phase having a second period interval with a duty ratio of 50%. The PWM signal generating unit 32 generates PWM signals for each phase having a second period interval, and the second period interval includes a fourth interval Q4 for turning on a part of the arms in the fourth energization mode during the idling period of the rotor, a fifth interval Q5 for turning on a part of the arms in the fifth energization mode during the idling period of the rotor, and a sixth interval Q6 for turning on all the upper arms or all the lower arms in the sixth energization mode during the idling period of the rotor. Fig.19 In the example shown, the second cycle section includes the fourth section Q4 including the first detection timing, the fifth section Q5 including the second detection timing, and the sixth section Q6 in which all upper arms are turned on. The current detection unit 27 subtracts half of the sum of the third current value and the fourth current value from the third current value of the second phase flowing into the current detector 24 in the fourth section Q4 or the fourth current value of the second phase flowing into the current detector 24 in the fifth section Q5. In this example, the current detection unit 27 can calculate the offset current value of the second phase by performing the operation of subtracting from the fourth current value. Fig.19 The example shows a case where the second phase is phase W. It should be noted that the second period section may be a section adjacent to the first period section, may be a section sandwiched between one or more period sections and the first period section, or may be the same section as the first period section.

[0109] For example, the current detection unit 27 can correct the current value of the phase current of the first phase flowing into the current detector 24 when the inverter 23 is rotating the rotor based on the offset current value of the first phase. Similarly, the current detection unit 27 can correct the current value of the phase current of the second phase flowing into the current detector 24 when the inverter 23 is rotating the rotor based on the offset current value of the second phase. For example, the first phase is the U phase and the second phase is the W phase, but other combinations are possible.

[0110] The current detection unit 27 can detect (calculate) the offset current value of the third phase based on the offset current value of the first phase and the offset current value of the second phase, using a formula that the sum of the phase currents of the three phases is zero. The third phase is, for example, the V phase. The current detection unit 27 can correct the phase current of the third phase flowing into the current detector 24 when the inverter 23 is rotating the rotor based on the detected (calculated) offset current value of the third phase.

[0111] For example, the current detection unit 27 calculates the offset current value of the first phase, calculates the offset current value of the second phase, and then calculates the offset current value of the remaining third phase based on these calculation results, and then stores the calculated offset current values ​​of the three phases in the memory. After the offset current values ​​of the three phases are stored in the memory, the motor 4 is started by the inverter 23, and the inverter 23 rotates the rotor.

[0112] When the inverter 23 is rotating the rotor, the current detection unit 27 performs current detection at least twice to detect the current value of each of the three-phase phase currents. The current detection unit 27 calculates the current detection value of each of the three-phase phase currents Iu, Iv, and Iw by subtracting the three-phase offset current value pre-stored in the memory from the current value of each of the three-phase phase currents detected in accordance with each cycle of the PWM signal. According to this, the current detection unit 27 can correct the phase current of each phase flowing into the current detector 24 when the inverter 23 is rotating the rotor according to the offset current value of each phase, so that the detection error can be removed from the current detection value of each of the three-phase phase currents Iu, Iv, and Iw. The PWM signal generation unit 32 generates the PWM signal of the three phases when the inverter 23 is rotating the rotor by using the current detection value of each of the three-phase phase currents Iu, Iv, and Iw after correction, and the detection error is removed, so that the rotation of the motor 4 can be controlled with high accuracy by the inverter 23.

[0113] It should be noted that the functions of the current detection unit 27, the power-on pattern generation unit 35, the current detection timing adjustment unit 34, and the initial position estimation unit 38 are implemented by the CPU (Central Processing Unit) running a program readable and stored in a storage device (not shown). For example, these functions are implemented by the cooperation of hardware and software in a microcomputer including a CPU.

[0114] The motor control device, the motor system and the motor control method are described above through the implementation modes, but the present invention is not limited to the above implementation modes, and various modifications and improvements can be made to the above implementation modes without departing from the technical scope described in the claims.

[0115] For example, a current detector that outputs a detection signal corresponding to the current value of the current flowing into the DC side of the inverter may be a current detector that outputs a detection signal corresponding to the current value of the current flowing into the positive bus (positive side bus). In addition, the current detector may also be a sensor such as a CT (Current Transformer).

[0116] The present international application claims the benefit of priority based on Japanese Patent Application No. 2020-064148 filed on March 31, 2020, and the entire contents of Japanese Patent Application No. 2020-064148 are incorporated herein by reference.

[0117] Description of reference numerals:

[0118] 1-1 Motor system

[0119] 4 Motor

[0120] 21 DC power supply

[0121] 22a Positive busbar

[0122] 22b Negative busbar

[0123] 23 Inverter

[0124] 24 Current detector

[0125] 27 Current detection unit

[0126] 30 Vector control unit

[0127] 32 PWM signal generation unit

[0128] 33. Driving circuit

[0129] 34 Current detection timing adjustment section

[0130] 35 Power-on pattern generation unit

[0131] 36 Clock signal generation unit

[0132] 37 Carrier generation unit

[0133] 38 Initial position estimation unit

[0134] 100-1 Motor control device

[0135] Up, Vp, Wp, Un, Vn, Wn arms.

Claims

1. A motor control device comprising: an inverter for energizing a motor having a rotor by turning on a portion of arms having different energization patterns among all arms; A current detector connected to the DC side of the inverter; a PWM signal generating unit that generates PWM signals of each phase having a first period interval by using a duty ratio having the same value, wherein the first period interval includes a first period in which the part of the arms is turned on in a first energization mode during an idling period of the rotor, a second period in which the part of the arms is turned on in a second energization mode during the idling period, and a third period in which all upper arms or all lower arms of all the arms are turned on in a third energization mode during the idling period; and The current detection unit calculates an offset current value of the first phase during the idling period by subtracting half of the sum of the first current value and the second current value from the first current value of the first phase flowing into the current detector during the first interval or the second current value of the first phase flowing into the current detector during the second interval.

2. The motor control device according to claim 1, wherein: The current detection unit corrects a current value of a phase current of the first phase flowing into the current detector when the inverter is rotating the rotor, based on an offset current value of the first phase during the idling period.

3. The motor control device according to claim 2, wherein: The PWM signal generating unit generates a PWM signal of the first phase when the inverter is rotating the rotor, using a current value of the corrected phase current of the first phase.

4. The motor control device according to claim 1, wherein: The PWM signal generating unit generates the PWM signals of the phases having a second period interval by using duty ratios having the same value, the second period interval including a fourth period in which the arms of the part are turned on in a fourth energization mode during the idling period, a fifth period in which the arms of the part are turned on in a fifth energization mode during the idling period, and a sixth period in which all upper arms or all lower arms of all arms are turned on in a sixth energization mode during the idling period, The current detection unit calculates the offset current value of the second phase during the idling period by subtracting half of the sum of the third current value and the fourth current value from the third current value of the second phase flowing into the current detector in the fourth interval or the fourth current value of the second phase flowing into the current detector in the fifth interval.

5. The motor control device according to claim 4, wherein: The current detection unit corrects a current value of a phase current of the second phase flowing into the current detector when the inverter is rotating the rotor, based on an offset current value of the second phase during the idling period.

6. The motor control device according to claim 5, wherein: The PWM signal generating unit generates a PWM signal of the second phase when the inverter is rotating the rotor, using a current value of the corrected phase current of the second phase.

7. The motor control device according to claim 4, wherein: The current detection unit calculates an offset current value of the third phase during the idling period based on the offset current value of the first phase during the idling period and the offset current value of the second phase during the idling period, and corrects the current value of the phase current of the third phase flowing into the current detector when the inverter is rotating the rotor based on the offset current value of the third phase during the idling period.

8. The motor control device according to claim 7, wherein: The PWM signal generating unit generates a PWM signal of the third phase when the inverter is rotating the rotor, using a current value of the corrected phase current of the third phase.

9. The motor control device according to claim 1, wherein: The identical value is 50%.

10. A motor system comprising: The motor control device as claimed in claim 1; and The motor.

11. A motor control method performed by a motor control device, the motor control device energizing a motor having a rotor by turning on a portion of arms of all arms of an inverter each having a different energization pattern, the motor control method comprising the following steps: generating PWM signals of each phase having a first period interval by using duty ratios having the same value, the first period interval including a first period in which the arms of the part are turned on in a first energization mode during an idling period of the rotor, a second period in which the arms of the part are turned on in a second energization mode during the idling period, and a third period in which all upper arms or all lower arms of all arms are turned on in a third energization mode during the idling period; and The offset current value of the first phase during the idling period is calculated by subtracting half of the sum of the first current value and the second current value from the first current value of the first phase flowing into the current detector connected to the DC side of the inverter during the first interval or the second current value of the first phase flowing into the current detector during the second interval.

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