Motor demagnetization detection method and motor demagnetization detection device

A motor demagnetization detection method includes the following steps. The speed of a motor is calculated according to the rotation angle of the motor. When determining that the motor respectively maintains a first and second steady state according to the speed, the three-phase current values of the motor are received to obtain first and second steady-state data. An equivalent magnetic flux is calculated according to the first and second steady-state data. The motor is repeatedly driven to maintain the first and second steady states, the first and second steady-state data are updated according to the three-phase current values, and the equivalent magnetic flux is again calculated to generate equivalent magnetic fluxes. A magnetic flux change is calculated according to equivalent magnetic fluxes. A demagnetization warning is issued according to a comparison of the magnetic flux change and a demagnetization warning value.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of China Patent Application No. 202110149162.1, filed on Feb. 3, 2021, the entirety of which is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a motor detection method and a motor detection device, and in particular it relates to a motor demagnetization detection method and a motor demagnetization detection device for detecting a magnetic flux change.

BACKGROUND

In general, a permanent magnet synchronous motor does not require additional excitation current to generate a rotor magnetic field, and has the advantages of high efficiency, low inertia, and high power density. In recent years, permanent magnet synchronous motors have been widely used in industrial applications, such as electric vehicles, robotic arms, elevators, etc.

On the other hand, it is common to add a field weakening control to the control of a permanent magnet synchronous motor, i.e., an appropriate demagnetization current is added to the direct axis (or d axis) of the permanent magnet synchronous motor to extend the operating range of the speed. However, excessive direct axis current may cause permanent demagnetization of the rotor magnet, thereby reducing motor performance. In addition, as the temperature of the rotor increase, the direct axis current that permanently demagnetizes the magnet also decreases, so that the permanent magnet synchronous motor more easily undergoes permanent demagnetization. Therefore, how to effectively detect demagnetization occurring in a motor or electric motor has become an important issue.

SUMMARY

An embodiment of the present invention provides a motor demagnetization detection method and a motor demagnetization detection device, thereby effectively estimating a magnetic flux, decreasing the errors in estimation of the magnetic flux, and increasing the accuracy of demagnetization detection.

An embodiment of the present invention provides a motor demagnetization detection method suitable to detect demagnetization of a motor. The motor demagnetization detection method includes the following steps. An encoder is used to estimate the rotation angle of the motor. A current sensing device is used to estimate the three-phase current value of the motor. The speed of the motor is calculated according to the rotation angle. When determining that the motor maintains a first steady state according to the speed, the three-phase current value is received to obtain and store a first steady-state data. When determining that the motor maintains a second steady state according to the speed, the three-phase current value is received to obtain and store a second steady-state data. An equivalent magnetic flux is calculated and stored according to the first steady-state data and the second steady-state data. The motor is repeatedly driven to maintain the first steady state and the second steady state, the first steady-state data and the second steady-state data are updated according to the three-phase current value, and the equivalent magnetic flux is again calculated and stored to generate a plurality of equivalent magnetic fluxes. A magnetic flux change is calculated according to the equivalent magnetic fluxes. A demagnetization warning is issued according to a comparison result of the magnetic flux change and a demagnetization warning value.

An embodiment of the present invention provides a motor demagnetization detection device suitable to detect demagnetization of a motor. The motor demagnetization detection device includes an encoder, a current sensing device and a controller. The encoder is configured to estimate the rotation angle of the motor. The current sensing device is configured to estimate the three-phase current value of the motor. The controller is coupled to the encoder and the current sensing device. The controller calculates the speed of the motor according to the rotation angle. When the controller determines that the motor maintains a first steady state according to the speed, the controller receives the three-phase current value to obtain and store a first steady-state data. When the controller determines that the motor maintains a second steady state according to the speed, the controller receives the three-phase current value to obtain and store a second steady-state data. The controller calculates and stores an equivalent magnetic flux according to the first steady-state data and the second steady-state data. The motor is repeatedly driven to maintain the first steady state and the second steady state, the controller updates the first steady-state data and the second steady-state data according to the three-phase current value, and again calculates and stores the equivalent magnetic flux to generate a plurality of equivalent magnetic fluxes. The controller calculates a magnetic flux change according to the equivalent magnetic fluxes, and the controller issues a demagnetization warning according to a comparison result of the magnetic flux change and a demagnetization warning value.

According to the motor demagnetization detection method and the motor demagnetization detection device disclosed by the present invention, when determining that the motor maintains the first steady state according to the speed of the motor, the three-phase current value is received to obtain and store the first steady state date. When determining that the motor maintains the second steady state according to the speed of the motor, the three-phase current value is received to obtain and store the second steady-state data. The equivalent magnetic flux is calculated and stored according to the first steady-state data and the second steady-state data. The motor is repeatedly driven to maintain the first steady state and the second steady state, the first steady-state data and the second steady-state data are updated according to the three-phase current value, and the equivalent magnetic flux is again calculated and stored to generate a plurality of equivalent magnetic fluxes. The magnetic flux change is calculated according to the equivalent magnetic fluxes. A demagnetization warning is issued according to the comparison result of the magnetic flux change and the demagnetization warning value. Therefore, the convenience of debug operation and use may be effectively increased. Therefore, it may effectively estimate the magnetic flux and decrease the magnetic flux estimation error generated by non-linear characteristics of the integrated circuit, so as to increase the accuracy of detecting demagnetization, and it may not use the motor parameters (such as the d axis inductance) related to the motor, so as to increase the convenience and accuracy of detection.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

In each of the following embodiments, the same reference number represents an element or component that is the same or similar.

FIG.1is a schematic view of a motor demagnetization detection device according an embodiment of the present invention. In the embodiment, the motor demagnetization detection device100is suitable to detect demagnetization of a motor device150, wherein the motor150may include an inverter151and a motor152. The inverter151may output a three-phase current value ia, iband icaccording to a control command to drive the motor152, so that the motor152operates. In the embodiment, the motor demagnetization detection device100may first receive a speed command, and generate the control command to the inverter151according to the speed command. In some embodiments, the motor152is, for example, a permanent magnet synchronous motor, and the motor152may be applied to elevators, electric vehicles, robotic arms, etc., but the embodiment of the present invention is not limited thereto. Furthermore, the motor device150further include a rectifier153. The rectifier153is coupled to the inverter151, and provide a rectified voltage to the inverter151. In addition, the rectifier153is, for example, a full bridge rectifier, but the embodiment of the present invention is not limited thereto.

Please refer toFIG.1. The motor demagnetization detection device100may include an encoder110, a current sensing device120and a controller130.

The encoder110estimates the rotation angle of the motor device150(such as the motor152) to output a motor position signal. In the embodiment, the encoder110may be a position sensor.

The current sensing device120is configured to estimate the three-phase current value of the motor device150(such as the motor152). Furthermore, the current sensing device120is coupled to an output terminal of the inverter151, and estimates the three-phase current value ia, iband icoutput by the inverter151to generate a current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband ic.

In some embodiments, the current sensing device120may include two current sensors210and220, as shown inFIG.2. The current sensors210and220are configured to estimate a first phase current (such as ia) and a second phase current (such as ib) of the three-phase current value ia, iband icoutput by the inverter151to generate the corresponding current detection value (such as ia′ and ib′). The controller130may calculates the detection current value (such as ic′) corresponding to the third phase current (such as ic) of the three-phase current value according to the current detection value (such as ia′) corresponding to the first phase current (such as ia) and the current detection value (such as ib′) of the second phase current (such as ib).

In some embodiments, the current sensing device120may include three current sensors310,320and330. The current sensors310,320and330are configured to estimate a first phase current (such as ia), a second phase current (such as ib) and a third phase current (such as ic) of the three-phase current value ia, iband icoutput by the inverter151, so that the current sensing device120may generate the current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband ic. It is particularly noted that the current sensors210,220,310,320and330may be Hall sensors or current sensing resistors, but the present invention is not limited thereto.

The controller130is coupled to the inverter151, the encoder110and the current sensing device120. The controller130may provide the control command to the inverter151. The controller130may receive the motor position signal output by the encoder110and the current detection value generated by the current sensing device120, and the controller130may calculate the speed of the motor152(the motor device150) according to the motor position signal (such as the rotation angle). Typically, the controller130determines the rotation angle of the motor152according to the motor position signal, and differentiates the rotation angle of the motor152to obtain the speed of the motor152.

Then, the controller130may determine whether the motor device150(such as the motor152) maintains a first steady state according to the speed of the motor152(for example, determining whether the speed of the motor152is maintained at a first operating speed for more than a first predetermined time and within a first error range). In the embodiment, the first operating speed is, for example, 1000 rpm, and the first error range is, for example, 5%. That is, the controller130may determine whether the speed of the motor152is maintained within 5% of the first operating speed, for example, between 950 rpm and 1050 rpm. However, the first operating speed being 1000 rpm and the first error range being 5% is only an exemplary embodiment of the present invention, but the embodiment of the present invention is not limited thereto. In other embodiments, the user may set the first operating speed to 800 rpm, 900 rpm, 1100 rpm, 1200 rpm, etc., and the first error range to 2%, 8%, 10%, 15%, etc., according to the requirements thereof.

When the controller130determines that the motor device150(such as the motor152) does not maintain the first steady state (for example, the speed of the motor152is not maintained at the first operating speed for more than the first predetermined time and within the first error range), the controller130may continue to calculate the speed of the motor152according to the motor position signal output by the encoder110, so as to determine again whether the motor device150(such as the motor152) maintains the first steady state.

When the controller130determines that the motor device150(such as the motor152) maintains the first steady state (for example, the speed of the motor152is maintained at the first operating speed for more than the first predetermined time and within the first error range), the controller130may receive the current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband icto obtain and store a first steady-state data. In the embodiment, the first steady-state data may include a first direct axis current (such as id1), a first direct axis voltage (such as vd1), a first quadrature axis current (such as iq1) and a first quadrature axis voltage (such as vq1).

Then, the controller130may determine whether the motor device150(such as the motor152) maintains a second steady state according to the obtained speed of the motor152(for example, determining whether the speed of the motor152is maintained at a second operating speed for more than a second predetermined time and within a second error range). In the embodiment, the second operating speed is, for example, 50 rpm, and the second error range is, for example, 10%. That is, the controller130may determine whether the speed of the motor152is maintained within 10% of the second operating speed, for example, between 45 rpm and 55 rpm. However, the second operating speed being 50 rpm and the second error range being 10% is only an exemplary embodiment of the present invention, but the embodiment of the present invention is not limited thereto. In other embodiments, the user may set the second operating speed to 30 rpm, 40 rpm, 60 rpm, 80 rpm, etc., and the second error range to 5%, 8%, 15%, etc., according to the requirements thereof.

In an embodiment, the first operating speed, the second operating speed, the first error range and the second error range are program setting values of the controller130. Usually, the second operating speed is lower than the first operating speed, but the present invention is not limited thereto. In other embodiments, the second operating speed is usually zero, for example: the speed of the motor of an elevator system. When the elevator cage reaches the designated floor, the speed of the motor of the elevator system is zero.

When the controller130determines that the motor device150(such as the motor152) does not maintain the second steady state (for example, the speed of the motor152is not maintained at the second operating speed for more than the second predetermined time and within the second error range), the controller130may continue to calculate the speed of the motor152according to the motor position signal output by the encoder110, so as to determine again whether the motor device150(such as the motor152) maintains the second steady state.

When the controller130determines that the motor device150(such as the motor152) maintains the second steady state (for example, the speed of the motor152is maintained at the second operating speed for more than the second predetermined time and within the second error range), the controller130may receive the current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband ic, to obtain and store a second steady-state data. In the embodiment, the second steady-state data may include a second direct axis current (such as id2), a second direct axis voltage (such as vd2), a second quadrature axis current (such as iq2) and a second quadrature axis voltage (such as vq2).

After the controller130obtain the first steady-state data and the second steady-state data, the controller130may obtain and store an equivalent magnetic flux according to the first steady-state data and the second steady-state data.

In the embodiment, the direct axis-quadrature axis (d-q axis) voltage equation of the motor152may be expressed as equation (1):

ddt
is a differential operator, ωeis a motor angular speed of the motor152and λm′ is an equivalent magnetic flux.

When the motor152operates at a steady state (for example, the speed of the motor152is maintained at the operating speed within the error range), equation (1) may be rewritten as equation (2), as shown below:

In addition, under a fixed load and at different speed (such as the first operating speed and the second operating speed) operating points, the quadrature axis voltages (such as the first quadrature axis voltage of the first steady-state data and the second quadrature axis voltage of the second steady-state data) are sampled, equation (3a) and equation (3b) may be obtained from equation (2), as shown below:
vq1=rsiq1+ωe1(Ldid1+λm′)  (3a)
vq2=rsiq2+ωe2(Ldid2+λm′)  (3b)

wherein vq1is the first quadrature axis voltage, iq1is the quadrature axis current, ωe1is the first operating speed, id1is the first direct axis current, vq2is the second quadrature axis voltage, iq2is the second quadrature axis current, ωe2is the second operating speed and id2is the second direct axis current.

Then, the first quadrature axis voltage vq1and the second quadrature axis voltage vq1obtained at the two speed operating points are subtracted, i.e., equation (3a) and equation (3b) are subtracted, to obtain equation (4), as shown below:
vq1−vq2=rs(iq1−iq2)+ωe1(Ldid1+λm′)−ωe2(Ldid2+λm′)  (4)

When the first quadrature axis current iq1≈the second quadrature axis current iq2and the first direct axis current id1≈the second direct axis current id2, equation (4) may be simplified to equation (5), as shown below:
vq1−vq2=(ωe1−ωe2)(Ldid1+λm′)  (5)

Then, equation (5) may be rewritten as equation (6), so as to estimate the equivalent magnetic flux.

wherein {circumflex over (λ)}m′ is the equivalent magnetic flux. That is, the controller130may estimate the equivalent magnetic flux according to equation (6), and store the equivalent magnetic flux.

Furthermore, if the direct axis current (such as the first direct axis current id1) is controlled to zero, equation (6) may be simplified to equation (7), as shown below:

That is, the controller130may also estimate the equivalent magnetic flux according to equation (7). It can be seen from equation (7) that equivalent magnetic flux {circumflex over (λ)}m′ may be calculated from the different operating speeds (such as the first operating speed and the second operating speed) and their corresponding quadrature axis voltages (such as the first quadrature axis voltage and the second quadrature axis voltage), and does not use the motor parameters (such as the direct axis inductance Ld) related to the motor152, thereby increasing the convenience and accuracy of detection.

Therefore, the equivalent magnetic flux corresponding to the motor152may be estimated by the controller to effectively determine the operating state of the motor, i.e., determining whether the temperature of the rotor of the motor152is too high, or determining whether the motor152has a phenomenon with demagnetization. For example, when the equivalent magnetic flux is lower than a predetermined threshold, it indicates that the temperature of the rotor of the motor152is too high, or the motor152has a phenomenon with demagnetization. Otherwise, when the equivalent magnetic flux is not lower than a predetermined threshold, it indicates that the temperature of the rotor of the motor152is not too high, or that the motor152does not have a phenomenon with demagnetization.

In some embodiments, the controller130may adjust the control command to the inverter151according to the motor position signal, the first steady-state data and the second steady-state data, so that the inverter151changes the three-phase current value to drive the motor152. As shown inFIG.1, the controller130may include a speed controller131, a current controller132, a modulation unit133, a speed calculator134, a three-phase to two-phase converter135and an estimating unit136, but the embodiment of the present invention is not limited thereto.

The speed controller131may receive the speed command ωm* and the speed of the motor152, and generate a current command according to the speed command ωm* and the speed of the motor152. The current controller132is coupled to the speed controller131, and receives the current command generated by the speed controller131, the direct axis current (such as the first direct axis current id1or the second direct axis current id2) and the quadrature axis current (such as the first quadrature axis current iq1or the second quadrature axis current iq1) to generate the direct axis voltage (such as the first direct axis voltage vd1or the second direct axis voltage vd2) and the quadrature axis voltage (such as the first quadrature axis voltage vq1or the second quadrature axis voltage vq2). Furthermore, when the current sensing device120senses the three-phase current value ia, iband ic, the current sensing device120output the current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband icto the three-phase to two-phase converter135. The three-phase to two-phase converter135converts the current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband icto the direct axis current (such as the first direct axis current id1or the second direct axis current id2) and the quadrature axis current (such as the first quadrature axis current iq1or the second quadrature axis current iq1).

The modulation unit133is coupled to the current controller132, receives the direct axis voltage (such as the first direct axis voltage vd1or the second direct axis voltage vd2) and the quadrature axis voltage (such as the first quadrature axis voltage vq1or the second quadrature axis voltage vq2) generated by the current controller132, performs a three-phase to two-phase conversion and a pulse width modulation for the direct axis voltage and the quadrature axis voltage to generate the control command, and provides the control command to the inverter151. Then, the inverter151may output the three-phase current value ia, iband icaccording to the control command generated by the modulation unit133, so as to drive the motor152to operate.

The speed calculator134is coupled to the encoder110, receives the motor position signal output by the encoder110, and calculates the motor position signal to generate the corresponding speed of the motor152. The three-phase to two-phase converter135is coupled to the current sensing device120, receives the current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband icgenerated by the current sensing device120, and converts the current detection value (such as ia′, ib′ and ic′) to two-phase direct axis current (such as the first direct axis current id1or the second direct axis current id2) and quadrature axis current (such as the first quadrature axis current iq1or the second quadrature axis current iq1).

The estimating unit136is coupled to the current controller132, the three-phase to two-phase converter135and the speed calculator134. The estimating unit136may receive the speed of the motor152provided by the speed calculator134, the first direct axis voltage, the first quadrature axis voltage, the second direct axis voltage and the second quadrature voltage provided by the current controller132and the first direct axis current, the first quadrature axis current, the second direct axis current and the second quadrature axis current provided by the three-phase to two-phase converter135.

The estimating unit136may determine whether the motor device150(such as the motor152) maintains the first steady state (for example, determining whether the speed of the motor152is maintained at the first operating speed for more than the first predetermined time and within the first error range). If the estimating unit136determines that the motor device150(such as the motor152) maintains the first steady state (for example, the speed of the motor152is maintained at the first operating speed for more than the first predetermined time and within the first error range), the estimating unit136may store the first steady-state data corresponding to the first steady state (for example, the speed of the motor152is maintained at the first operating speed).

In addition, the estimating unit136may also determine whether the motor device150(such as the motor152) maintains the second steady state (for example, determining whether the speed of the motor152is maintained at the second operating speed for more than the second predetermined time and within the second error range). If the estimating unit136determine that the motor device150(such as the motor152) maintains the second steady state (for example, the speed of the motor152is maintained at the second operating speed for more than the second predetermined time and within the second error range), the estimating unit136may store the second steady-state data corresponding to the second steady state (for example, the speed of the motor152is maintained at the second operating speed). Then, the estimating unit136may obtain and store the equivalent magnetic flux according to the first steady-state data and the second steady-state data.

In some embodiments, the controller130may further repeatedly generate the control command to the inverter151to repeatedly drive the motor152to maintain the first steady state and the second steady state, the controller130may update the first steady-state data and the second steady-state data according to the current detection value (such as ia′, ib′ and ic′) of the three-phase current value ia, iband ic, and again calculate and store the equivalent magnetic flux to generate a plurality of equivalent magnetic fluxes. In the embodiment, the calculation manner of the above equivalent magnetic fluxes may also be calculated using equation (6) or equation (7).

Then, the controller130may calculate magnetic flux change according to the above equivalent magnetic fluxes. In some embodiment, the controller130may capture a minimum value and a maximum value from the above equivalent magnetic fluxes. That is, the controller130may compare the above equivalent magnetic fluxes to obtain the minimum value and the maximum value. Then, the controller130may calculate the magnetic flux change according to the minimum value and the maximum value of the above equivalent magnetic fluxes.

In addition, in some embodiments, the controller130captures an initial value and a final value from the above equivalent magnetic fluxes. That is, the controller130may sort the equivalent magnetic fluxes to obtain the initial value and the final value. Then, the controller130may calculate the magnetic flux change according to the initial value and the final value of the above equivalent magnetic fluxes. In the embodiment, the magnetic flux change may be calculated using equation (8), as shown below:

wherein Δ{circumflex over (λ)}m′ is the magnetic flux change, {circumflex over (λ)}m′(k) is the initial value and {circumflex over (λ)}m′(k−n) is the final value.

After the controller130calculates the magnetic flux change, the controller130may issue a demagnetization warning according to a comparison result of the magnetic flux change and a demagnetization warning value, so as to determine whether the motor152has a phenomenon with demagnetization. In the embodiment, the demagnetization warning value may be adjusted by the user according to the requirements thereof, such as 5% or 10%, but the embodiment of the present invention is not limited thereto.

For example, the controller130may compare the magnetic flux change with the demagnetization warning value, so as to determine whether the magnetic flux change is greater than or equal to the demagnetization warning value (for example, determining whether magnetic flux change is greater than or equal to 5% or 10%) and generate the comparison result. When the comparison result is that the magnetic flux change is less than the demagnetization warning value, the controller130does not issue a demagnetization warning. Therefore, the controller130may determine that the motor152does not have a phenomenon with demagnetization, and the controller130may continue the detection operation of the magnetic flux change or end the detection operation. When the comparison result is that the magnetic flux change is greater than or equal to the demagnetization warning value, the controller130may issue a demagnetization warning. Therefore, the controller130may determine that the motor152has a phenomenon with demagnetization, and perform a load reduction operation and issue a demagnetization warning signal. Accordingly, the demagnetization warning signal will let the user know that the motor152has a phenomenon with demagnetization, and that repairing or replacing the motor152may be required.

In some embodiments, the controller130includes a storage unit (not shown), so that the controller130may store the calculated equivalent magnetic flux in the storage unit, wherein the storage unit may be a memory, an electrically-erasable programmable read-only memory (EEPROM), etc.

According to the above-mentioned description, the embodiment of the present invention additionally provides a motor demagnetization detection method.FIG.4is a flowchart of a motor demagnetization detection method according an embodiment of the present invention. In the embodiment, the motor demagnetization detection method is suitable to detect demagnetization of a motor. In step S402, the method involves using an encoder to estimate the rotation angle of the motor.

In step S404, the method involves using a current sensing device to estimate the three-phase current value of the motor. In step S406, the method involves calculating the speed of the motor according to the rotation angle. In step S408, the method involves when determining that the motor maintains a first steady state according to the speed, receiving the three-phase current value to obtain and store a first steady-state data.

In step S410, the method involves when determining that the motor maintains a second steady state according to the speed, receiving the three-phase current value to obtain and store a second steady-state data. In step S412, the method involves calculating and storing an equivalent magnetic flux according to the first steady-state data and the second steady-state data.

In step S414, the method involves repeatedly driving the motor to maintain the first steady state and the second steady state, updating the first steady-state data and the second steady-state data according to the three-phase current value, and again calculating and storing the equivalent magnetic flux to generate a plurality of equivalent magnetic fluxes. In step S416, the method involves calculating a magnetic flux change according to the equivalent magnetic fluxes. In step S418, the method involves issuing a demagnetization warning according to a comparison result of the magnetic flux change and a demagnetization warning value.

In the embodiment, the first steady-state data may include the first direct axis current, the first direct axis voltage, the first quadrature axis current and first quadrature axis voltage. The second steady-state data may include the second direct axis current, the second direct axis voltage, the second quadrature axis current and the second quadrature axis voltage.

Furthermore, in some embodiments, step S416may include capturing a minimum value and a maximum value of the plurality of equivalent magnetic fluxes, and calculating the magnetic flux change according to the minimum value and the maximum value. In some embodiments, step S416may include capturing an initial value and a final value of the plurality of equivalent magnetic fluxes, and calculating the magnetic flux change according to the initial value and the final value. In some embodiments, step S418may include issuing a demagnetization warning when the comparison result is that the magnetic flux change is greater than or equal to the demagnetization warning value; and not issuing the a demagnetization warning when the comparison result is that the magnetic flux change is less than the demagnetization warning value.

It should be noted that the order of the steps ofFIG.4is only for illustrative purposes, and is not intended to limit the order of the steps of the present invention. The user may change the order of the steps above to meet specific requirements. The flowcharts described above may add additional steps or use fewer steps without departing from the spirit and scope of the present invention.

FIG.5is a waveform diagram of a speed of a motor and a quadrature axis current when a motor demagnetization detection device drives the motor according an embodiment of the present invention. InFIG.5, a curve S1indicates the speed of the motor152, a curve S2indicates the quadrature current, a reference number Speed1indicates the first operating speed, a reference number Speed2indicates the second operating speed, reference numbers T1˜T5indicate time. In addition, in the embodiment, the motor152is a motor of an elevator system for example, and the elevator cage rises from the first floor to the fifth floor, for example.

At time T1, when the elevator cage starts to operate from the first floor, a motor brake device releases the motor152, and the current value of the quadrature axis current S1increases, so that the motor152starts to operate and accelerate. Then, at time T2, when the elevator cage reaches between the second floor and the third floor, the speed of the motor152may reach the first operating speed Speed1and maintain the first operating speed Speed1. That is, the motor device150(such as the motor152) maintains the first steady state. At this time, the controller130of the motor demagnetization detection device100may obtain and store the first steady-state data. Afterward, at time T3, after the elevator cage reaches the third floor, the current value of the quadrature axis current S1decrease, so that the motor152starts to decelerate. Then, at time T4, the speed of the motor152may reach the second operating speed Speed2and maintain the second operating speed Speed2. That is, the motor device150(such as the motor152) maintains the second steady state. At this time, the controller130of the motor demagnetization detection device100may obtain and store the second steady-state data. Finally, at time T5, when the elevator cage reaches the fifth floor, the motor brake device may clamp the motor152, so that the motor152stop operating and the speed of the motor152is decreased to zero, and then the elevator cage is maintained on the fifth floor.

In summary, according to the motor demagnetization detection method and the motor demagnetization detection device disclosed by the embodiment of the present invention, when determining that the motor maintains the first steady state according to the speed of the motor, the three-phase current value is received to obtain and store the first steady state date. When determining that the motor maintains the second steady state according to the speed of the motor, the three-phase current value is received to obtain and store the second steady-state data. The equivalent magnetic flux is calculated and stored according to the first steady-state data and the second steady-state data. The motor is repeatedly driven to maintain the first steady state and the second steady state, the first steady-state data and the second steady-state data are updated according to the three-phase current value, and the equivalent magnetic flux is again calculated and stored to generate a plurality of equivalent magnetic fluxes. The magnetic flux change is calculated according to the equivalent magnetic fluxes. A demagnetization warning is issued according to the comparison result of the magnetic flux change and the demagnetization warning value. Therefore, it may effectively estimate the magnetic flux and decrease the magnetic flux estimation error generated by non-linear characteristics of the integrated circuit, so as to increase the accuracy of detecting demagnetization, and it may not use the motor parameters (such as the d axis inductance) related to the motor, so as to increase the convenience and accuracy of detection.