JP2003348898A - Phase loss detection method for motor control device - Google Patents

Abstract

(57) An object of the present invention is to provide an electric motor control device capable of detecting a phase failure with high accuracy regardless of whether or not a current command is changed. An inverter device 3 for controlling an induction motor 1, a vector control device 5 for calculating an ignition signal of a semiconductor element constituting the inverter device 3 based on an input torque command, and an induction motor 1 A method for detecting an open phase of an electric motor control device including a current detector 2 for detecting a phase current, the inverter frequency Fi based on the phase current of the induction motor 1 detected by the current detector 2
A coordinate converter 12 that calculates the d-axis current and the q-axis current on the rotation coordinate synchronized with nv, and a subtractor 1 that calculates the change rate of the d-axis current based on the calculated d-axis current value.
5 and a comparator 16 that outputs an open phase detection signal when the calculated change rate of the d-axis current exceeds a set value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase loss detection method for a motor control device, and more particularly to a phase loss detection method for a motor control device for detecting phase loss of a motor control device having an inverter device.

[0002]

2. Description of the Related Art Generally, in a control device for an electric motor that drives an electric vehicle or the like, if a ground fault of the induction motor or a lack of wiring or the like from the inverter control device to the induction motor occurs, it is necessary to omit them. Although this is called a phase, if such a situation occurs, it is necessary to detect the phase loss promptly, stop the operation of the inverter control device, and prevent failure of the elements constituting the inverter control device. .

Therefore, as an open phase detection method, for example, there is an open phase detection method for an electric vehicle disclosed in Japanese Patent Application Laid-Open No. 06-245301. FIG. 7 is a block diagram showing a method for detecting an open phase of the electric vehicle. In FIG. 7, 51 is an induction motor that drives an electric vehicle, 52 is a VVVF inverter device that controls the induction motor 51, 53 is a CT for phase current detection, 54 is a logic unit, 55 is an overhead line, 56 is a pantograph, and 57 is cut off. vessel,
58 represents a reactor, and 59 represents a capacitor. FIG. 8 shows a detailed internal configuration of the logic unit 54. FIG.
54-1 is a means for converting each phase current iU, iV, iW into absolute values | iU |, | iV |, | iW |
-2 is a means for calculating the average value IU, IV, IW of the absolute value of each phase current, and 54-3 is the average value I0 (=
Means for calculating (IU + IV + IW) / 3), 54-4
Is the difference between the average value of each phase current and these three average values I0 | I
Means for calculating U−I0 |, | IV−I0 |, | IW−I0 |, 54-5 is a comparing means for comparing these differences with a reference value ΔI (output of the reference value setting means 54-6), 54 -7
Represents a logical means.

Normally, the overhead line 55 to the pantograph 56,
A DC voltage is applied to the VVVF inverter device 52 through the circuit breaker 57, the reactor 58 and the capacitor 59,
The three-phase alternating current converted by the VVVF inverter device 52 is supplied to the induction motor 51 to drive and control the electric vehicle. Now, for example, it is assumed that a one-phase disconnection abnormality occurs in the W phase of the main circuit on the outfitting side (point A) and no current flows. In this case, U
Since all the currents flowing from the phases return to the V phase, the three-phase currents flowing in the U, V, and W phases in the normal state become single-phase currents flowing only in the U and V. The logic unit 54 captures these phase currents and detects this difference. This relationship will be described with reference to FIGS.

FIG. 9 describes the normal state. The phase currents iU, iV, iW flowing through the U, V, W phases from the VVVF inverter device 52 are out of phase by 120 degrees as shown in FIG. Each phase current iU, i
V and iW are detected by the phase current detection CT 53 and input to the logic unit 54. Means 54 for converting each phase current into an absolute value
−1, these absolute values | iU |, | iV |, |
If iW | is taken, the result is as shown in (b). Further, in the means 54-2 for calculating the average value of each phase current, when the average value is taken, as shown in (c), IU, IV, IW and Become. Therefore, means 54- for calculating these three average values 54-
3, the average value I0 = (IU + IV + IW) / 3 is calculated, and the difference | I is calculated in the means 54-4 for calculating the difference between the average value of each phase current and these three average values I0.
When U−I0 |, | IV−I0 |, | IW−I0 | are calculated, the absolute value thereof becomes zero. As a result, the comparing means 54
At -5, the absolute value is the appropriately chosen reference value ΔI
It is determined that the value is smaller than (reference value setting means 54-6), and a normal signal of the phase current is output from the logic means 54-7.

FIG. 10 shows each current waveform when there is a one-phase disconnection abnormality in the W phase as described above. The phase current is
Since single-phase currents iU and iV flowing only in the U and V phases are obtained,
The phase relationship between the U phase and the V phase is 180 degrees as shown in FIG. Therefore, as described in FIG. 9, the absolute values | iU |, | iV |, | iW |, and the average value I
When U, IV, and IW are taken, they are as shown in (b) and (c), respectively, and only the average value of the W phase becomes zero. Average value of each phase and average value of these three values I0 (= (IU + IV + IW)
/ 3), the absolute value | IU−I0 |, | I
V-I0 | and | IW-I0 | are not zero but take a certain value. At this time, since the reference value ΔI is selected as an appropriate value, a certain value becomes larger than the reference value ΔI, and the logic means 54
Phase current abnormality signal is output from -7, and phase current phase loss detection is performed.

The above has described the single-phase disconnection failure in the W phase of the main circuit on the equipment side. However, the single-phase disconnection failure in the U and V phases of the main circuit on the equipment side, and the one-phase disconnection and main One-phase disconnection on the motor circuit can be detected in the same manner. Similarly, when the CT itself fails, for example, when the CT cannot detect the W-phase current, the W-phase detection current is zero and the average value is zero. As a result, the absolute value of the difference between the average value of each phase and the average value I0 (= (IU + IV + IW) / 3) | IU−I0 |, | IV−I0 |, | IW−I0 |
Takes a certain value without becoming zero, and is larger than the reference value ΔI, and therefore outputs an abnormal signal. Similarly, it is also possible to detect a failure such as a ground fault on the motor side where the main circuit current escapes somewhere and a failure from the inverter control device input to the CT output. Induction motor 5
1 'may be a parallel circuit as shown by a dotted line in FIG. 7, and a part of the circuit may be disconnected. However, since the average value of each phase current is used, an open phase of the phase current is detected. There is no inconvenience above.

[0008]

The conventional phase loss detection method for electric vehicles has the above-described configuration and operation, and phase loss detection can also be performed with this method. However, because phase loss is detected by focusing on the rate of change in phase current of induction motors, phase current fluctuations caused by changes in current command and current due to phase loss due to idling re-adhesion control, overhead wire voltage limiter control, etc. There is a problem that it is not possible to distinguish between fluctuations, and there is a possibility that an open phase may be erroneously detected depending on a set value of the open phase detection even though it is normal.

The present invention has been made to solve such a problem, and a phase loss detection method for an electric motor control device capable of accurately detecting phase loss regardless of whether or not a current command has changed. The purpose is to obtain.

[0010]

The present invention relates to an inverter device for controlling an induction motor by converting DC power to AC power, and a semiconductor element constituting the inverter device based on an input torque command. A phase failure detection method for a motor control device for detecting a phase failure of a motor control device comprising a vector control device for calculating a starting signal of the motor and a current detector for detecting a phase current of the induction motor. A current calculation step for calculating a d-axis current and a q-axis current on a rotation coordinate synchronized with the inverter frequency of the inverter device based on the phase current of the induction motor detected by the current detector; Based on the value of the d-axis current, a change rate calculating step for calculating the change rate of the d-axis current, and when the calculated change rate of the d-axis current exceeds a set value, A phase loss detection method of a motor control apparatus having an open phase detecting step of outputting a detection signal.

Further, the present invention further comprises a limiting step of inputting the rate of change of the d-axis current calculated in the rate of change calculating step and limiting and outputting the value of the rate of change, wherein the phase loss detecting step comprises: The phase loss is detected using the rate of change limited in the limiting step.

The set value used in the phase loss detection step is variable.

The second phase loss detection signal is output when the phase loss detection signal output in the phase loss detection step is input and the output of the phase loss detection signal continues for a predetermined time. The phase loss detection step is further provided.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. FIG. 1 is a block diagram showing a phase failure detection method in the motor control apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a detailed configuration of the logic unit 4 in FIG. In FIG. 1, 1 is an induction motor for driving an electric car, 2a to
2c represents phase currents Iu and I flowing in the induction motor 1, respectively.
A current detector for detecting v and Iw, 3 is an inverter device for supplying AC power to the induction motor 1, 4 is a logic unit for detecting a phase loss, and 5 is an ignition signal of a main circuit element constituting the inverter device 3. This is a vector control device for calculation. 6 is an overhead line, 7 is a pantograph that collects DC power from the overhead line 6,
8 is a DC circuit breaker, 9 is a filter reactor, and 10 is a filter capacitor.

In FIG. 2, reference numeral 11 denotes an inverter frequency F.
An integrator that integrates inv and calculates a phase θ, 12 is a d on a dq coordinate (rotating coordinate axis) that rotates in phase with the inverter frequency Finv using the phase θ from the phase currents Iu, Iv, and Iw. A coordinate converter that calculates an axial current and a q-axis current, 13 detects a maximum value of the d-axis current in a predetermined time, and outputs a maximum d-axis current;
A minimum current detector 15 for detecting a minimum value of the d-axis current in a predetermined time and outputting a d-axis minimum current, 15 subtracts the d-axis minimum current from the d-axis maximum current, and d-axis current deviation ΔIDF
(Ie, a subtractor for calculating the change rate of the d-axis current), 1
A comparator 6 compares an arbitrary set value ΔIDR with a current deviation ΔIDF, and outputs a phase loss detection signal PUD when the current deviation ΔIDF is larger than the set value ΔIDR.

Next, the operation will be described with reference to FIGS. FIG. 3 is a timing chart showing changes in each current value in the motor control device according to the present embodiment.
First, DC power is collected from the overhead line 6 through the pantograph 7, via the circuit breaker 8 and the filter reactor 9,
A DC voltage is input to the inverter device 3. The filter capacitor 10 constitutes an LC filter together with the filter reactor 9 and is installed to reduce the influence of the switching effect of the inverter device 3 on the overhead line 6.

The inverter device 3 includes a vector control device 5
The electric vehicle is driven by converting the input DC voltage into a three-phase AC voltage and supplying it to the induction motor 1 in accordance with the firing command of the element output by.

Current detectors 2a to 2c detect phase currents Iu, Iv and Iw flowing through induction motor 1, and output the signals to logic unit 4. In the logic part 4, as shown in FIG.
The inverter frequency Finv is integrated by the integrator 11 to calculate the phase θ, and the current converter 12 calculates the phase θ.
Are used to convert the phase currents Iu, Iv, and Iw into d-axis current and q-axis current on the dq coordinate rotating in synchronization with the inverter frequency Finv. Then, the d-axis current and the q-axis current are output to the vector control device 5.

The vector control device 5 performs current control so that the current command calculated by the command from the host system matches the d-axis current IDF and the q-axis current IQF calculated by the logic unit 4, respectively. The ignition signal of the semiconductor element which comprises the inverter apparatus 3 is output.

In the logic unit 4, the d-axis current IDF is input to the maximum current detector 13 and the minimum current detector 14, and the d-axis current deviation ΔIDF is calculated from each output by the subtractor 15. The arbitrary set value ΔIDR is compared with the current deviation ΔIDF, and when the current deviation ΔIDF is larger than the set value ΔIDR, the phase loss detection signal PUD is output.

In the normal state, as shown in part (A) of FIG. 3, the d-axis current IDF and the q-axis current IQF are constant values, and the d-axis current deviation ΔIDF is almost zero. In this state, the set value ΔIDR is set to a sufficiently large value with respect to the d-axis current deviation, so that the phase loss detection signal PUD is not output (becomes “L” level).

In addition, in order to change the output torque of the motor, such as idling re-adhesion control, as control unique to the electric vehicle,
As shown in part (B) of FIG. 3, the q-axis current IQF may be changed, but even in this case, the d-axis current IDF does not fluctuate.
D is not output ("L" level).

Next, when one of the wirings between the inverter device 3 and the motor 1 is disconnected, the d-axis current IDF and the q-axis current IQF fluctuate as shown in part (C) of FIG. At this time, the d-axis current deviation ΔIDF fluctuates as shown in part (C) of FIG. 3, and when this value becomes larger than the set value ΔIDR, the phase loss detection signal PUD is output (“H "Become level". In this case, vector control 5
Can immediately stop the ignition signal to prevent a failure of the semiconductor elements constituting the inverter device 3.

As described above, according to the phase loss detection method of the motor control apparatus of FIG. 1, the phase loss can be detected by the logic unit 4 using the fluctuation (change rate) of the d-axis current. ,
By using the idling re-adhesion control and overhead wire voltage limiter control specific to electric vehicles, it is possible to distinguish between phase current fluctuations due to current command changes and current fluctuations due to phase loss, and to detect phase loss accurately. . Further, as described above, even when the wiring is disconnected or the current detector fails, the phase loss is reliably detected, and the ignition signal is immediately stopped, so that the semiconductor device constituting the inverter device 3 can be stopped. Failure can be prevented.

Embodiment 2 FIG. FIG. 4 shows a phase loss detection method in the motor control apparatus according to Embodiment 2 of the present invention. 4 shows only the configuration of the portion corresponding to the vicinity of the comparator 16 in the logic unit 4 shown in FIG. In the present embodiment, as shown in FIG. 4, a limiter 21 for limiting the magnitude of the current deviation ΔIDF is provided between the subtracter 15 and the comparator 16 in FIG. Since the other whole structure is the same as FIG. 1 and FIG. 2, it attaches | subjects and shows the same code | symbol and abbreviate | omits description here. In the phase failure detection method of the motor control device shown in FIG.
Current deviation ΔIDF calculated by the subtractor 15 in the logic unit 4
4 is input to the comparator 16. However, in the phase loss detection method of the motor control device shown in FIG. 4, the limited second current deviation ΔIDF2 output from the limiter 21 that limits the magnitude of the current deviation ΔIDF is obtained. This is output to the comparator 16.

In FIG. 4, a limiter 21 limits the current deviation ΔIDF and outputs a second current deviation ΔIDF2. Note that the phase loss detection method of the motor control device shown in FIG. 4 can be applied to the phase loss detection method of the motor control device shown in FIG.

Next, the operation of the second embodiment will be described. The limiter 21 receives the current deviation ΔIDF. In the limiter 21, a maximum value ΔIDFmax and a minimum value ΔIDFmin of the current deviation ΔIDF are set in advance.

The input current deviation ΔIDF is the current deviation ΔIDF.
When the IDF is greater than the maximum value ΔIDFmax, the second current deviation ΔIDF2 is the maximum value Δ of the current deviation ΔIDF.
IDFmax is output.

When the input current deviation ΔIDF is smaller than the minimum value ΔIDFmin of the current deviation ΔIDF,
The minimum value ΔIDFmin of the current deviation ΔIDF is output as the second current deviation ΔIDF2.

When the input current deviation ΔIDF is smaller than the maximum value ΔIDFmax of the current deviation ΔIDF and larger than the minimum value ΔIDFmin of the current deviation ΔIDF, the input current deviation ΔIDF is the second current deviation ΔIDF2. Needless to say, it is output as is.

In the comparator 16, instead of the current deviation ΔIDF, the second current deviation ΔIDF2 and an arbitrary set value ΔI
DR is compared with the second current deviation Δ from the set value ΔIDR.
When IDF2 is large, the phase loss detection signal PUD is output.

As described above, in the present embodiment,
While obtaining the same effect as the first embodiment,
Further, a limiter 21 is provided between the subtractor 15 and the comparator 16.
And the second current deviation ΔI input to the comparator 16 is provided.
Since the value of DF2 was limited, the current deviation ΔID
It can be avoided that F becomes a value which is impossible in the use range due to, for example, a calculation error.

Embodiment 3 FIG. FIG. 5 shows another embodiment of the phase loss detection method of the motor control device as Embodiment 3 of the present invention. FIG. 5 shows only the configuration of the portion corresponding to the vicinity of the comparator 16 in the logic unit 4 shown in FIG. 2 or FIG. In the present embodiment, as shown in FIG.
A table 22 for inputting IDR2 is provided. Since the other whole structure is the same as FIG.1, FIG.2 or FIG.4, it attaches | subjects and shows the same code | symbol and abbreviate | omits description here. 1 and 2 shown in the first and second embodiments.
4, the phase loss detection method of the motor control device 4 includes the comparator 16.
In addition, a fixed set value ΔIDR is set. However, in the phase loss detection method of the motor control device according to the present embodiment, the set value ΔIDR is made variable according to the inverter frequency.

In FIG. 5, an inverter frequency Finv is inputted to a table 22 and the inverter frequency F is inputted.
The second set value ΔIDR2 determined by inv is compared with the comparator 1
6 is output.

The phase loss detection method of the motor control device shown in FIG. 5 can be applied to the phase loss detection method of the electric vehicle shown in FIGS.

Next, the operation of the phase loss detection method of the motor control apparatus according to the present embodiment shown in FIG. 5 will be described. In the table 22, the inverter frequency Finv is input. The table 22 includes a second set value ΔIDR2 corresponding to each value of the inverter frequency Finv in advance.
Is remembered. The table 22 shows the second set value ΔIDR2 corresponding to the inverter frequency Finv as the comparator 1.
6 is output. In the comparator 16, the second set value ΔIDR
2 and current deviation ΔIDF or second current deviation ΔID
When the current deviation ΔIDF or the second current deviation ΔIDF2 is larger than the second set value ΔIDR2, the phase loss detection signal PUD is output.

As described above, in the present embodiment,
The same effects as those of the first and second embodiments described above can be obtained, and the set value ΔID input to the comparator 16 can be further obtained.
Since R2 can be made variable by the inverter frequency Finv, for example, it is possible to cope with a case where the threshold value for detecting the phase loss detection signal needs to be changed according to the operating state.

Embodiment 4 FIG. FIG. 6 shows another embodiment of the phase loss detection method of the motor control device as Embodiment 4 of the present invention. In the phase loss detection method of the motor control device shown in FIGS. 1, 4 and 5 shown in the above first to third embodiments, the output of the comparator 16 is directly used as the phase loss detection signal. In the phase loss detection method of the motor control device according to the embodiment, the phase loss detection signal output PUD of the comparator 16 is output to the second logic unit 23, and when the output PUD continues for a certain time in the logic unit 23 The second phase loss detection output PUD2 is output.

FIG. 6 shows only the configuration of the portion corresponding to the vicinity of the comparator 16 in the logic section 4 shown in FIG. In the present embodiment, as shown in FIG. 6, a second logic unit 23 is provided after the comparator 16 of FIG. Since the other whole structure is the same as FIG. 1 and FIG. 2, it attaches | subjects and shows the same code | symbol and abbreviate | omits description here.

In FIG. 6, the second logic unit 23 is input only when the output PUD of the comparator 16 and the set time TPUD are input and the output PUD of the comparator 16 continues for a preset set time TPUD. The second phase loss detection output PUD2 is output.

The phase failure detection method for the motor control device shown in FIG. 6 can be applied to the phase loss detection method for the motor control device shown in FIGS.

Next, the operation of the phase loss detection method of the motor control apparatus in this embodiment shown in FIG. 6 will be described.
The second logic unit 23 receives the phase loss detection output PUD. The set time TPUD is input to the second logic unit 23. The second logic unit 23 outputs the phase loss detection output PUD.
Measures the time when becomes “H”, and the time is set time TP
When it becomes larger than UD, the second phase loss detection output PU
D2 is output (becomes "H" level). In this case, the vector control device 5 can prevent failure of the elements constituting the inverter device 3 by immediately stopping the ignition signal.

As described above, in the phase loss detection method of the motor control device according to the present embodiment, the phase loss detection setting time TPUD (time element) is provided for phase loss detection.
For example, even when a case in which the threshold value for detecting the phase loss detection signal is instantaneously exceeded due to a disturbance or the like, malfunction of the phase loss detection can be prevented.

[0044]

The present invention provides an inverter device for controlling an induction motor by converting DC power to AC power, and an ignition signal for a semiconductor element constituting the inverter device based on an input torque command. A phase failure detection method for a motor control device for detecting a phase failure of a motor control device comprising a vector control device for calculating a phase current and a current detector for detecting a phase current of the induction motor, wherein the current detection A current calculation step for calculating a d-axis current and a q-axis current on a rotation coordinate synchronized with the inverter frequency of the inverter device based on the phase current of the induction motor detected by a generator; and the calculated d-axis current A change rate calculating step for calculating a change rate of the d-axis current based on the value, and when the calculated change rate of the d-axis current exceeds a set value,
Since the phase loss detection method of the motor control device includes a phase loss detection step for outputting a phase loss detection signal, the phase loss can be detected using the rate of change of the d-axis current. Thus, it is possible to distinguish between fluctuations in the phase current due to the change in the current command and current fluctuations due to the missing phase, and to detect the missing phase with high accuracy.

In addition, the method further comprises a limiting step for inputting the rate of change of the d-axis current calculated in the rate of change calculating step and limiting and outputting the value of the rate of change. Since the phase loss is detected using the rate of change limited in the limiting step, it is avoided that the rate of change of the current becomes an insignificant value in the operating range due to calculation error or the like. it can.

Further, since the set value used in the phase loss detection step is variable, it is possible to cope with a case where the threshold value of the phase loss detection signal output needs to be changed.

The second phase loss detection signal is output when the phase loss detection signal output in the phase loss detection step is input and the output of the phase loss detection signal continues for a predetermined time. In this case, it is possible to prevent malfunction even when, for example, the threshold value of the phase loss detection signal output is instantaneously exceeded due to disturbance or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a phase loss detection device of an electric motor control device according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of a logic unit of the phase loss detection device of the electric motor control device according to Embodiment 1 of the present invention.

FIG. 3 is an explanatory diagram showing a graph for explaining the operation of the phase loss detection device of the electric motor control device according to Embodiment 1 of the present invention;

FIG. 4 is a partial block diagram showing a configuration of a logic part of a phase loss detection device of an electric motor control device according to Embodiment 2 of the present invention.

FIG. 5 is a partial block diagram showing a configuration of a logic part of an open phase detector of an electric motor controller according to Embodiment 3 of the present invention.

FIG. 6 is a partial block diagram showing a configuration of a logic part of a phase loss detection device of an electric motor control device according to Embodiment 4 of the present invention.

FIG. 7 is a block diagram showing a configuration of a phase loss detection device of a conventional motor control device.

FIG. 8 is a block diagram showing a configuration of a logic unit in a phase loss detection device of a conventional motor control device.

FIG. 9 is an explanatory diagram showing waveforms showing an operation in a normal state in a conventional electric vehicle phase loss detection device.

FIG. 10 is an explanatory diagram showing a waveform showing an operation when there is an abnormality of a single-phase disconnection in the W phase in a conventional phase loss detection device for an electric vehicle.

[Explanation of symbols]

1 induction motor, 2a, 2b, 2c current detector, 3
Inverter device, 4 logic unit, 5 vector control device, 6
Overhead line, 7 pantograph, 8 DC circuit breaker, 9 filter reactor, 10 filter capacitor, 11 integrator, 12 coordinate converter, 13 maximum current detector, 14
Minimum current detector, 15 subtractor, 16 comparator, 21
Limiter, 22 table, 23 second logic part, 51
Induction motor, 52 VVVF inverter device, 53
CT for phase current detection, 54 logic section, 55 overhead line, 56
Pantograph, 57 circuit breaker, 58 reactor, 59
Capacitor, 54-1 conversion means, 54-2 means for calculating average values IU, IV, IW of absolute values of respective phase currents, 54
-3 means for calculating average value I0, 54-4 means for calculating difference between average value of each phase current and I0, 54-5 comparing means, 54
-6 Reference value setting means, 54-7 Logic means.

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Claims (4)

[Claims] 1. An inverter device for controlling an induction motor by converting DC power into AC power, and a vector for calculating an ignition signal of a semiconductor element constituting the inverter device based on an input torque command A phase failure detection method for a motor control device for detecting a phase failure of a motor control device comprising a control device and a current detector for detecting a phase current of the induction motor, wherein the phase detection method is detected by the current detector. Further, based on the phase current of the induction motor, a current calculation step for calculating the d-axis current and the q-axis current on the rotation coordinate synchronized with the inverter frequency of the inverter device, and based on the calculated d-axis current value A change rate calculating step for calculating a change rate of the d-axis current, and an open phase detection signal for outputting a phase loss detection signal when the calculated change rate of the d-axis current exceeds a set value. And a step of detecting an open phase of the motor control device. 2. The method further comprises a limiting step of inputting the rate of change of the d-axis current calculated in the rate of change calculating step and limiting and outputting the value of the rate of change, wherein the phase loss detecting step comprises: The phase loss detection method of the motor control device according to claim 1, wherein phase loss detection is performed using the rate of change limited in the limiting step. 3. The set value used in the phase loss detection step is variable.
Or a phase loss detection method of the motor control device according to 2; 4. A second phase loss detection signal that outputs a second phase loss detection signal when the phase loss detection signal output in the phase loss detection step is input and the output of the phase loss detection signal continues for a predetermined time. The phase loss detection method for an electric motor control device according to any one of claims 1 to 3, further comprising: a phase loss detection step.