TW202208874A - Method of detecting connection fault of electric motor - Google Patents

Abstract

A method of detecting a connection fault of an electric motor, applies to a driving mechanism of an inverter, and includes steps of: capturing a three-phase stator current of an electric motor, transforming the three-phase stator current to acquire two current components in a stationary coordinate, calculating a rotating angle of the electric motor according to the two current components, calculating an angular velocity according to the rotating angle, comparing a frequency of the angular velocity with a frequency of an output voltage of the inverter, and determining that the electric motor occurs a connection fault if a difference between the frequency of the angular velocity and the frequency of the output voltage is greater than a predetermined value.

Description

Motor connection fault detection method

The present invention relates to a motor connection fault detection method, especially a motor connection fault detection method by performing operations in a stationary coordinate system.

Please refer to FIG. 1 , which is a schematic diagram of an open circuit of a three-phase motor. As shown in the figure, the three-phase (eg, U, V, W three-phase) output power output terminals of the inverter 10A need to be firmly connected to the motor 20A so that the motor 20A can properly operate according to the output of the inverter 10A. However, once the motor 20A is opened due to the disconnection of the power line, the output power of the inverter 10A cannot be normally transmitted to the motor 20A, so that the motor 20A cannot operate normally.

Taking the elevator system as an example, when the motor 20A has an open circuit, the torque cannot be output normally. At this time, it is necessary to immediately detect the fault and start the mechanical brake to stop the elevator car body from moving, so as to avoid the elevator car body in a state that cannot be controlled normally. Continue to move, causing loss of life and property of passengers and damage to the system. It should be noted that the motor open-circuit fault or short-circuit fault is a type of motor connection fault.

Therefore, how to design a motor connection fault detection method to solve the aforementioned technical problems is an important subject studied by the inventor of the present application.

The purpose of the present invention is to provide a motor connection fault detection method to solve the problems of the prior art.

In order to achieve the purpose disclosed above, the motor connection fault detection method proposed by the present invention is applied to the open-loop drive structure of the frequency converter. The detection method includes: capturing the three-phase stator current of the motor; converting the three-phase stator current to obtain the The two-axis current components of the static coordinate system; the rotation angle of the motor is calculated according to the two-axis current components; the angular velocity is calculated according to the rotation angle; the frequency of the angular velocity is compared with the frequency of the output voltage of the inverter; and if the frequency of the angular velocity and the output voltage of the inverter The difference of the frequency is greater than the frequency setting difference, then it is judged that the motor is a connection failure.

In one embodiment, if the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than the frequency setting difference, and the state continues for more than a predetermined time, it is determined that the motor is a connection failure.

In one embodiment, the frequency setting difference is 5 Hz.

With the proposed open-loop (open-loop) motor connection fault detection method, connection faults such as open-circuit faults or short-circuit faults can be detected immediately, so as to avoid the loss of life and property and system damage caused by the continuous operation of the motor.

Another object of the present invention is to provide a motor connection fault detection method to solve the problems of the prior art.

In order to achieve the aforementioned purpose, the motor connection fault detection method proposed by the present invention is applied to the closed-loop drive structure of the frequency converter. The detection method includes: capturing the three-phase stator current fed back by the motor; converting the three-phase stator current, Obtain the multi-axis current components in the static coordinate system; obtain the two-axis current command of the inverter in the synchronous coordinate system; convert the two-axis current command in the synchronous coordinate system to obtain the multi-axis current command of the inverter in the static coordinate system; and compare The multi-axis current command and multi-axis current components in the static coordinate system are obtained to obtain the multi-axis current error value in the static coordinate system. When the current error value of any axis is greater than the current setting difference, the motor is determined as a connection failure.

In one embodiment, the multi-axis current command of the stationary coordinate system may be a two-axis current command or a three-axis current command, and the multi-axis current component of the stationary coordinate system may be a two-axis current component or a feedback three-phase stator current, The multi-axis current error value may be a two-axis current error value or a three-axis current error value.

In one embodiment, it further includes adding the absolute value of the two-axis current error value or the three-axis current error value to obtain the total current error value; and if the total current error value is greater than the total current setting difference, determining that the motor is connected Fault.

In one embodiment, the total current setting difference is 3.5% of the maximum rated output current.

In one embodiment, if the total current error value is greater than the total current setting difference, and the state continues for more than a predetermined time, it is determined that the motor is a connection failure.

In one embodiment, the current setting difference of any axis is 2% of the maximum rated output current of the inverter.

In one embodiment, if the current error value of any axis is greater than the current set difference value, and the state continues for more than a predetermined time, it is determined that the motor is a connection failure.

With the proposed closed-loop (closed-loop) motor connection fault detection method, connection faults such as open-circuit faults or short-circuit faults can be detected immediately, so as to avoid the loss of life and property and system damage caused by the continuous operation of the motor.

In order to further understand the technology, means and effect adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and accompanying drawings of the present invention. For specific understanding, however, the accompanying drawings are only provided for reference and description, and are not intended to limit the present invention.

The technical content and detailed description of the present invention are described as follows in conjunction with the drawings.

Take open-loop control, such as voltage/frequency (V/f) proportional control as an example, because this open-loop control only outputs the corresponding voltage according to the frequency, and there is no information on the rotor position and current vector, etc., so if only the scalar current difference is used. The method of detecting connection failures such as motor open-circuit failures or short-circuit failures makes it difficult to set the current threshold.

Therefore, in the open-loop drive structure of the inverter, the method of the present invention for determining whether the motor is connected to a fault such as an open-circuit fault or a short-circuit fault is performed by using the frequency of the angular velocity converted and calculated by the motor current and the frequency of the output voltage of the inverter. Comparison, if the difference between the two is less than a frequency setting difference, it is determined that the multi-phase motor has no connection failure; on the contrary, if the difference between the two is greater than the frequency setting difference, it is determined that the multi-phase motor has a connection failure. The aforementioned The multi-phase motor is, for example, a three-phase motor or a six-phase motor. The present invention mainly takes a three-phase motor as an example, and the detailed description is as follows.

及

)。透過轉換，可將三相的定子電流(

,

,

)轉換為兩軸的α/β座標系的定子電流。亦即，靜止座標系與定子電流純量之間的關係如下：Please refer to FIG. 2 , which is a schematic diagram of the three-phase current and static coordinate system of the present invention. The present invention discloses the steps of a motor connection fault detection method, which is applied to an open-loop drive structure of an inverter, and the connection fault may include an open-circuit fault or a short-circuit fault. Referring to FIG. 3 , it is a system schematic diagram of the first embodiment of the motor connection fault detection method of the present invention; as shown in FIG. 4 , it is a flow chart of the first embodiment of the motor connection fault detection method of the present invention. . 4 is used as the main description, this method is applied to the open-loop drive structure of the inverter: first, a three-phase stator current fed back by a motor is captured (step S11 ). In this embodiment, the three-phase motor is detected Open circuit fault is used as an illustration, but it can also be applied to six-phase motor, and can also be applied to short circuit fault detection, which will be explained. Then, the three-phase stator currents are converted to obtain two-axis current components in a stationary coordinate system (step S12). Wherein, the stationary coordinate system is also called α/β (alpha/beta) coordinate system (shown as

and

). Through conversion, the three-phase stator current (

,

,

) into the stator current of the two-axis α/β coordinate system. That is, the relationship between the stationary coordinate system and the stator current scalar is as follows:

(1)

(1)

為定子電流純量的最大值、

為合成電流與參考軸的夾角。in,

is the maximum value of the stator current scalar,

is the angle between the resultant current and the reference axis.

,

)。Therefore, the three-phase stator current can be converted through the relation (1) to obtain the two-axis current component in the stationary coordinate system (

,

).

Then, a rotation angle of the motor is calculated according to the two-axis current components in the stationary coordinate system (step S13). Among them, the calculation (estimation) of the stator current vector angle is as follows (relationship (2)):

(2)

(2)

Then, an angular velocity is calculated based on the rotation angle (step S14). Specifically, by differentiating the rotation angle, the angular velocity can be obtained as follows (relationship (3)):

(3)

(3)

Then, the frequency of the angular velocity and the frequency of the output voltage of the inverter are compared (step S15). Under the allowable error range, since the motor angular velocity is converted and calculated from the motor current, the frequency of the motor angular velocity is close to the frequency of the stator current, so comparing the frequency of the motor angular velocity and the frequency of the output voltage of the inverter is an alternative. An embodiment of comparing the frequency of the motor stator current with the frequency of the output voltage of the frequency converter, wherein the frequency converter is used to drive and control the motor.

，這個估計的角速度的頻率

基本上與驅動控制該馬達的變頻器的輸出電壓的頻率

應該相等(在不考慮誤差的理想狀態下)，因此，本發明利用馬達的定子電流的頻率與變頻器的輸出電壓的頻率應該相同的特性，透過馬達的定子電流轉換並計算角速度的頻率，並且與變頻器的輸出電壓的頻率進行比較。一旦兩者差異過大時，即可判定馬達為連接故障。反之，若該角速度的頻率與該變頻器的輸出電壓的頻率的差異小於或等於該頻率設定差值，則判定該馬達無連接故障。換言之，透過對定子電流進行角速度估測，可得知馬達在正常連接及驅動狀態下(即無發生開路故障或短路故障)，經由定子電流轉換並計算的角速度的頻率與變頻器實際輸出的電壓的頻率應該相當接近，甚至相同。再者，由於經由回授定子電流轉換並計算以估測角速度的頻率的響應快速，可即時地追隨變頻器的輸出電壓的頻率，因此，可利用回授定子電流轉換並計算以估測角速度的頻率這個資訊快速地進行馬達連接故障與否的檢測。Finally, according to the result of the comparison, it is judged whether the connection failure of the motor occurs. Specifically, if the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than a frequency setting difference, it is determined that the motor has a connection failure (step S16 ). because

, the frequency of this estimated angular velocity

Basically the frequency of the output voltage that drives the inverter that controls the motor

should be equal (in the ideal state without considering the error), therefore, the present invention utilizes the characteristic that the frequency of the stator current of the motor and the frequency of the output voltage of the inverter should be the same, and the frequency of the angular velocity is converted and calculated through the stator current of the motor, and Compare with the frequency of the output voltage of the inverter. Once the difference between the two is too large, the motor can be judged as a connection failure. On the contrary, if the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is less than or equal to the set frequency difference, it is determined that the motor has no connection fault. In other words, by estimating the angular velocity of the stator current, it can be known that the frequency of the angular velocity converted and calculated by the stator current and the actual output voltage of the inverter when the motor is in a normal connection and driving state (that is, no open-circuit fault or short-circuit fault occurs) The frequencies should be fairly close, or even the same. Furthermore, since the frequency of the angular velocity estimated by the feedback stator current conversion and calculation has a fast response, the frequency of the output voltage of the inverter can be followed in real time. Therefore, the feedback stator current can be converted and calculated to estimate the angular velocity. The frequency information enables quick detection of motor connection failure or not.

)可為5赫茲，然不以此為限制本發明。亦即，若該角速度的頻率與該變頻器的輸出電壓的頻率的差異大於5赫茲，因為在連接正常時定子電流的頻率應與變頻器的輸出電壓的頻率相同，則根據此頻率差異過大的現象判定馬達為連接故障。上述馬達包括三相馬達或六相馬達，上述連接故障包括開路故障或短路故障。In this embodiment, the frequency setting difference (

) can be 5 Hz, but this does not limit the present invention. That is, if the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than 5 Hz, because the frequency of the stator current should be the same as the frequency of the output voltage of the inverter when the connection is normal, then according to this frequency difference is too large. The phenomenon determines that the motor is a connection failure. The above-mentioned motor includes a three-phase motor or a six-phase motor, and the above-mentioned connection fault includes an open-circuit fault or a short-circuit fault.

In different embodiments, in order to avoid the influence of noise, it is erroneously judged that a motor connection failure occurs. Therefore, it can be designed that even if the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than 5 Hz (that is, the frequency of the Frequency setting difference), it is not immediately judged that a motor connection failure occurs, but it is further judged whether this state (exceeding the frequency setting difference) continues and exceeds a predetermined time, such as 4 milliseconds, but this is not a limitation. invention. In other words, when the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than the frequency setting difference, and the state where the difference exceeds the frequency setting difference continues and exceeds the predetermined time, the motor is determined to be connected Fault. Conversely, when the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than the frequency setting difference, but the state does not last and does not exceed the predetermined time, it is determined that the motor has no connection fault. In this way, there is an additional time mechanism for auxiliary judgment, which can prevent the influence of noise from causing the instantaneous (transient) difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter to be greater than the set frequency difference, and misjudgment as occurrence Motor connection failure. The above-mentioned motor includes a three-phase motor or a six-phase motor, and the above-mentioned connection fault includes an open-circuit fault or a short-circuit fault.

,

,

) (步驟S21)，本實施例以偵測三相馬達開路故障作為示意，惟亦可應用於六相馬達，且亦可應用於短路故障偵測，予以說明。然後，轉換該三相定子電流，得到在一靜止座標系的兩軸電流分量或三軸電流分量(步驟S22)。其中，所述靜止座標系亦稱為α/β(alpha/beta)座標系(圖示為

及

)。透過轉換，可將三相的定子電流(

,

,

)轉換為兩軸的α/β座標系的定子電流；若欲取得靜止座標系的三軸電流值，可直接取用回授的該三相定子電流(

,

,

)。亦即，靜止座標系定子電流純量之間的關係如下：Please refer to FIG. 5 , which is a schematic diagram of the three-phase current, the stationary coordinate system and the synchronous coordinate system of the present invention. The steps of the motor connection fault detection method of the present invention are applied to a closed-loop drive structure of a frequency converter, and the connection fault may include an open-circuit fault or a short-circuit fault. Referring to FIG. 6 , it is a system schematic diagram of the second embodiment of the motor connection fault detection method of the present invention; as shown in FIG. 7 , it is a flow chart of the second embodiment of the motor connection fault detection method of the present invention. . The following is the main description of the process shown in Fig. 7. This method is applied to the closed-loop drive structure of the inverter. First, a three-phase stator current fed back by a motor is extracted (

,

,

) (step S21 ), the present embodiment takes the detection of an open circuit fault of a three-phase motor as an illustration, but it can also be applied to a six-phase motor, and can also be applied to the detection of a short-circuit fault. Then, the three-phase stator currents are converted to obtain two-axis current components or three-axis current components in a stationary coordinate system (step S22). Wherein, the stationary coordinate system is also called α/β (alpha/beta) coordinate system (shown as

and

). Through conversion, the three-phase stator current (

,

,

) into the stator current of the two-axis α/β coordinate system; if you want to obtain the three-axis current value of the static coordinate system, you can directly use the feedback of the three-phase stator current (

,

,

). That is, the relationship between the stator current scalars in the stationary coordinate system is as follows:

(4)

(4)

,

,

)得到在靜止座標系的兩軸電流分量(

,

)；需說明的是，如圖6所示同步座標系上的電流命令與回授的馬達定子電流均可依需要區分不同實施例進行多軸轉換，例如分別轉換成靜止座標系上的兩軸電流命令或三軸電流命令與兩軸電流分量或三軸電流分量，再進行比較以達故障偵測目的，其中回授的靜止座標系上的三軸電流分量可直接取用前述回授的三相定子電流值(

,

,

)以簡化及加速運算。Therefore, through the relationship (4), the three-phase stator current can be converted (

,

,

) to obtain the two-axis current components in the stationary coordinate system (

,

); it should be noted that, as shown in FIG. 6, the current command on the synchronous coordinate system and the feedback motor stator current can be divided into different embodiments for multi-axis conversion according to needs, for example, they are respectively converted into two axes on the static coordinate system. The current command or the three-axis current command is compared with the two-axis current component or the three-axis current component for the purpose of fault detection. The three-axis current component on the feedback static coordinate system can be directly obtained from the three-axis current component of the feedback. Phase stator current value (

,

,

) to simplify and speed up operations.

)以及一交軸(q軸)電流命令(

。Then, two-axis current commands of the inverter in a synchronous coordinate system are obtained (step S23). Wherein, the synchronous coordinate system is a dq-axis rotation coordinate system. The two-axis current command of the inverter in the synchronous coordinate system refers to the straight-axis (d-axis) current command (

) and a quadrature axis (q axis) current command (

.

Then, convert the two-axis current command of the synchronous coordinate system to obtain the two-axis current command or three-axis current command of the inverter in the static coordinate system (step S24), wherein the current command of the synchronous coordinate system is converted to the two-axis current command of the static coordinate system. and the relationship between the three-axis current command are shown in the following equations (5a) and (5b) respectively:

(5a)

(5a)

(5b)

(5b)

,

)得到在靜止座標系的兩軸電流命令(

,

)或三軸電流命令(

,

,

)。Therefore, the two-axis current command in the synchronous coordinate system can be converted (

,

) to obtain the two-axis current command in the stationary coordinate system (

,

) or triaxial current command (

,

,

).

)與所對應在靜止座標系的交軸電流分量(

)相減，可得到在靜止座標系的交軸的電流誤差值

。同樣地，透過將在靜止座標系的直軸電流命令(

)與所對應在靜止座標系的直軸電流分量(

)相減，可得到在靜止座標系的直軸的電流誤差值

。然後，將交軸的電流誤差值與直軸的電流誤差值分別取絕對值後相加，可得到該總電流誤差值。前述交軸的電流誤差值

、直軸的電流誤差值

或總電流誤差值均可用以判斷馬達是否為連接故障，至於三軸的比對方式類似，且所述電流設定差值或所述總電流設定差值可以依據需要分別設定或統一設定，本發明不以此為限。Then, the biaxial current command in the stationary coordinate system is compared with the biaxial current component in the stationary coordinate system in one embodiment, or the triaxial current in the stationary coordinate system is compared in another embodiment Command and the three-axis current component (ie, the feedback of the three-phase stator current value) in the stationary coordinate system to obtain the two-axis current error value or the three-axis current error value in the stationary coordinate system, respectively, wherein , as long as the current error value of any axis is greater than a current setting difference value, it is determined that the motor is a connection failure (step S25 ). Furthermore, the absolute value of the two-axis current error value or the three-axis current error value calculated above can also be added to obtain a total current error value in the stationary coordinate system, and finally, according to the comparison of the total current error value Whether the result is greater than a total current setting difference determines whether the motor has a connection failure, that is, if the total current error value is greater than the total current setting difference, the motor is determined to be a connection failure (step S26 ). The embodiment in which the two-axis components are converted into the stationary coordinate system is taken as an example to illustrate, by converting the quadrature-axis current command in the stationary coordinate system (

) and the corresponding quadrature current component in the stationary coordinate system (

), the current error value in the quadrature axis of the stationary coordinate system can be obtained

. Likewise, by changing the direct-axis current command in the stationary coordinate system (

) and the corresponding direct-axis current component in the stationary coordinate system (

), the current error value in the direct axis of the stationary coordinate system can be obtained

. Then, the absolute value of the current error value of the quadrature axis and the current error value of the direct axis are respectively taken as absolute values and added to obtain the total current error value. Current error value of the aforementioned quadrature axis

, the current error value of the straight axis

Or the total current error value can be used to judge whether the motor is a connection failure, as for the three-axis comparison method is similar, and the current setting difference or the total current setting difference can be set separately or uniformly according to needs, the present invention Not limited to this.

,

)，應該與同步座標系的電流命令(

,

)轉換至靜止座標系的電流命令(

,

)相近，即靜止座標系回授的電流值(

,

)會追隨靜止座標系的電流命令(

,

)進行調節(即調整、改變輸出電壓使實際電流與電流命令一致)，因此，本發明利用這樣的特性，藉由比較電流誤差值是否超過所預設的電流設定差值，確認靜止座標系回授的電流值是否無法追隨靜止座標系的電流命令，據此判定此時馬達發生連接故障。在本實施例中，該電流設定差值為該變頻器額定輸出電流最大值的2%，然不以此為限制本發明。一旦直軸或交軸中的任一軸電流誤差值過大而超過該單軸的電流設定差值時，或該多軸的總電流誤差值過大而超過該多軸的總電流設定差值時，例如總電流誤差值超過該變頻器額定輸出電流最大值的3.5%，則可判定馬達為連接故障。反之，若直軸或交軸的電流誤差值均小於或等於該電流設定差值時，或該多軸的總電流誤差值小於或等於該多軸的總電流設定差值時，則判定該馬達無連接故障。換言之，透過確認直軸或交軸中的任一軸電流誤差值過大，或確認該總電流誤差值是否過大進行判斷，可得知馬達發生連接故障，因為在正常驅動狀態下(即無發生開路故障或短路故障)，靜止座標系回授的電流值(

,

)，應該與同步座標系的電流命令(

,

)轉換至靜止座標系的電流命令(

,

)相當接近，甚至相同。再者，無論馬達為暫態加速或穩態運轉時，由於靜止座標系回授的電流值(

,

)追隨靜止座標系的電流命令(

,

)的響應快速，因此，可利用電流誤差值這個資訊快速地進行馬達連接故障與否的檢測。上述馬達包括三相馬達或六相馬達，上述連接故障包括開路故障或短路故障，亦可應用於兩軸或三軸的電流值比對。Because when the motor is normally connected and driven, the following is still an example of the embodiment converted to the two-axis components of the static coordinate system. The current value fed back by the static coordinate system (

,

), which should match the current command in the synchronous coordinate system (

,

) to the current command of the stationary coordinate system (

,

) is similar, that is, the current value fed back by the stationary coordinate system (

,

) will follow the current command in the stationary coordinate system (

,

) to adjust (that is, to adjust or change the output voltage to make the actual current consistent with the current command). Therefore, the present invention utilizes such a characteristic to confirm whether the static coordinate system returns to the current setting difference by comparing whether the current error value exceeds the preset current setting difference. Whether the given current value cannot follow the current command of the static coordinate system, it is judged that the motor has a connection failure at this time. In this embodiment, the current setting difference is 2% of the maximum rated output current of the frequency converter, but this does not limit the present invention. Once the current error value of any axis in the direct axis or quadrature axis is too large and exceeds the current setting difference of the single axis, or the total current error value of the multi-axis is too large and exceeds the total current setting difference of the multi-axis, for example If the total current error value exceeds 3.5% of the maximum rated output current of the inverter, it can be determined that the motor is a connection failure. Conversely, if the current error value of the direct axis or the quadrature axis is less than or equal to the current setting difference, or the total current error value of the multi-axis is less than or equal to the total current setting difference of the multi-axis, the motor is judged. No connection failures. In other words, by confirming that the current error value of any axis in the straight axis or the quadrature axis is too large, or confirming whether the total current error value is too large, it can be determined that the motor has a connection failure, because in the normal driving state (that is, no open circuit failure occurs) or short-circuit fault), the current value fed back by the static coordinate system (

,

), which should match the current command in the synchronous coordinate system (

,

) to the current command of the stationary coordinate system (

,

) are fairly close, even the same. Furthermore, no matter when the motor is in transient acceleration or steady state operation, the current value (

,

) follows the current command in the stationary coordinate system (

,

) has a fast response, so the information of the current error value can be used to quickly detect whether the motor connection is faulty or not. The above-mentioned motors include three-phase motors or six-phase motors, and the above-mentioned connection faults include open-circuit faults or short-circuit faults, and can also be applied to two-axis or three-axis current value comparison.

In different embodiments, in order to avoid the influence of noise, it is wrongly judged that a motor connection failure occurs. Therefore, it can be designed that even if the current error value of any axis in the direct axis or the quadrature axis is greater than 2 times the maximum rated output current of the inverter %, or the total current error value is greater than 3.5% of the maximum rated output current of the inverter, it is not immediately determined that a motor connection failure has occurred, but it is further determined whether the state continues and exceeds a predetermined time, such as 4 milliseconds, However, this does not limit the present invention. In other words, when the current error value of any axis in the direct axis or the quadrature axis is greater than the current setting difference, or the total current error value is greater than the total current setting difference, and the state continues and exceeds the predetermined time, it is determined that the The motor is faulty in connection. Conversely, even when the current error value of either the direct axis or the quadrature axis is greater than the current setting difference value, or the total current error value is greater than the total current setting difference value, but the state does not last and does not exceed the predetermined time, when Then it is determined that the motor has no connection failure. In this way, there is an additional time mechanism for auxiliary judgment, which can prevent the instantaneous (transient) current error value from being larger than the set value due to the influence of noise, and misjudging as a motor connection failure occurs. The above-mentioned motors include three-phase motors or six-phase motors, and the above-mentioned connection faults include open-circuit faults or short-circuit faults, and can also be applied to two-axis or three-axis current value comparison.

To sum up, the present invention has the following features and advantages:

1. The application range of the motor connection fault detection method proposed by the present invention can widely cover the existing control methods generally based on inverter drive architecture, such as V/f control, V/f-PG control, SVC control, FOC-PG control Control, FOC-PGPM control, etc., can be applied to the open-loop and closed-loop drive architecture of the inverter at the same time, but the numerical basis for the judgment is slightly different. The present invention can be applied to three-phase, six-phase or other multi-phase motors. The detection method proposed by the present invention can detect connection faults including open-circuit faults or short-circuit faults.

2. Compared with the method of measuring the signal response by exciting the current signal at different angles, the present invention does not need to inject additional signals to measure the current response, and the influence of the motor parameters is small, so the operation is simple and accurate.

3. Compared with the control method of judging that the negative sequence voltage is higher than the threshold value, the present invention directly uses the current to determine the judgment, which can ensure that the fault can be detected immediately when the current is abnormal.

4. Compared with the method of fault detection by detecting negative sequence voltage, three-phase voltage RMS error and total harmonic distortion, the present invention does not require a complete sampling cycle, and can detect faults within a short period of time when the fault occurs. .

With the proposed motor connection fault detection method, the connection fault can be detected immediately, so as to avoid the loss of life and property and the damage to the system caused by the continuous operation of the motor.

The above descriptions are only detailed descriptions and drawings of the preferred embodiments of the present invention, but the features of the present invention are not limited thereto, and are not intended to limit the present invention. The entire scope of the present invention should be defined as the following claims All the embodiments that conform to the spirit of the scope of the patent application of the present invention and similar variations thereof shall be included in the scope of the present invention. Modifications can be covered by the following patent scope of this case.

10A: Inverter

20A: Motor

S11~S16: Steps

S21~S26: Steps

Figure 1: It is a schematic diagram of an open circuit of a three-phase motor.

FIG. 2 is a schematic diagram of the three-phase current and static coordinate system of the present invention.

FIG. 3 is a system schematic diagram of the first embodiment of the motor connection fault detection method of the present invention.

FIG. 4 is a flowchart of the first embodiment of the motor connection fault detection method of the present invention.

FIG. 5 is a schematic diagram of three-phase current, static coordinate system and synchronous coordinate system of the present invention.

FIG. 6 is a system schematic diagram of a second embodiment of the motor connection fault detection method of the present invention.

FIG. 7 is a flowchart of a second embodiment of the motor connection fault detection method of the present invention.

S11~S16: Steps

Claims (10)

A motor connection fault detection method, applied to an open-loop drive structure of a frequency converter, includes: extracting a three-phase stator current of a motor; Convert the three-phase stator current to obtain two-axis current components in a stationary coordinate system; Calculate a rotation angle of the motor according to the two-axis current components; Calculate an angular velocity according to the rotation angle; comparing the frequency of the angular velocity with the frequency of an output voltage of the frequency converter; and If the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than a frequency setting difference, it is determined that the motor is a connection failure. The motor connection fault detection method as claimed in claim 1, wherein if the difference between the frequency of the angular velocity and the frequency of the output voltage of the inverter is greater than the frequency setting difference, and the state continues for more than a predetermined time, it is determined that The motor is faulty in connection. The motor connection fault detection method as claimed in claim 1, wherein the frequency setting difference is 5 Hz. A motor connection fault detection method, applied to a closed-loop drive structure of a frequency converter, includes: capturing a three-phase stator current fed back by a motor; Convert the three-phase stator current to obtain multi-axis current components in a stationary coordinate system; Obtain the two-axis current command of the inverter in a synchronous coordinate system; converting the two-axis current command in the synchronous coordinate system to obtain the multi-axis current command of the frequency converter in the stationary coordinate system; and Comparing the multi-axis current command and the multi-axis current component in the stationary coordinate system to obtain a multi-axis current error value in the stationary coordinate system, wherein when the current error value of any axis is greater than a current setting difference, it is determined that the The motor is faulty in connection. The motor connection fault detection method as claimed in claim 4, wherein the multi-axis current command of the stationary coordinate system can be a two-axis current command or a three-axis current command, and the multi-axis current component of the stationary coordinate system can be two-axis current command The shaft current component or the feedback of the three-phase stator current, the multi-axis current error value may be a two-axis current error value or a three-axis current error value. The motor connection fault detection method as described in claim 5, further comprising: adding the absolute value of the two-axis current error value or the three-axis current error value in the stationary coordinate system to obtain a total current error value; and If the total current error value is greater than a total current setting difference, it is determined that the motor has a connection failure. The motor connection fault detection method as claimed in claim 6, wherein the total current setting difference is 3.5% of the maximum rated output current of the inverter. The motor connection fault detection method as claimed in claim 6, wherein if the total current error value is greater than the total current setting difference, and the state continues for more than a predetermined time, the motor is determined to be a connection fault. The motor connection fault detection method as claimed in claim 4, wherein the current setting difference of the any axis is 2% of the maximum rated output current of the inverter. The motor connection fault detection method according to claim 4, wherein if the current error value of any axis is greater than the current setting difference, and the state continues for more than a predetermined time, the motor is determined to be a connection fault.

Images