Method for quantifying open-phase of motor, motor driving device, and storage medium

Abstract

The application relates to a motor open-phase quantification method, a motor driving device and a storage medium. The method comprises the following steps: turning off the bridge arm of a non-target phase, inputting a direct-current voltage into the target phase between three-phase terminals of a motor in sequence, and sampling to obtain a current of each target phase; determining a total resistance between phases according to the ratio of the direct-current voltage to the current of each target phase; determining the sum of two-phase contact resistances according to the difference between the total resistance between phases and a stator resistance; determining a phase contact resistance according to the sum of the two-phase contact resistances; and normalizing the phase contact resistance to determine the open-phase degree of the motor. The method can quantify the open-phase degree of the motor.

Description

Technical Field

[0001] This application relates to the field of motor technology, and in particular to a method for quantifying a phase loss in a motor, a motor drive device, and a storage medium. Background Technology

[0002] Motor drive systems (permanent magnet synchronous motors, asynchronous motors, etc. powered by inverters / frequency converters / servo drives) are widely used in industrial automation, electric drives for new energy vehicles, home appliances (air conditioner compressors), servo control, and other fields. Phase loss faults in the motor and its power supply circuit (disconnection or poor contact in a phase winding or connection terminal) are one of the common and serious fault types in motor drive systems. Traditional methods diagnose phase loss by applying DC voltage to the motor and determining whether the current in a particular phase is zero; this relies on a binary on / off condition and cannot quantify the degree of phase loss. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for quantifying motor phase loss, a motor drive device, and a storage medium that can quantify the degree of motor phase loss, in order to address the above-mentioned technical problems.

[0004] A method for quantifying phase loss in a motor, the method comprising: Turn off the bridge arm of the non-target phase, sequentially input DC voltage to the target phases of the three-phase terminals of the motor, and sample to obtain the current of each target phase; The total resistance between each phase is determined based on the ratio of the DC voltage to the current of each target phase. The sum of the contact resistances of each pair of phases is determined based on the difference between the total resistance between each phase and the stator resistance. The contact resistance of each phase is determined based on the sum of the contact resistances of each pair of phases; The phase loss degree of the motor is determined by normalizing the contact resistance of each phase.

[0005] A motor drive device, characterized in that it includes a method for quantifying phase loss in each motor, comprising: The voltage injection module is used to turn off the bridge arm of the non-target phase and sequentially input DC voltage to the target phases of the three-phase terminals of the motor. The current sampling module is used to sample and obtain the current of each target phase. The resistance determination module is used for: The total resistance between each phase is determined based on the ratio of the DC voltage to the current of each target phase. The sum of the contact resistances of each pair of phases is determined based on the difference between the total resistance between each phase and the stator resistance. The contact resistance of each phase is determined based on the sum of the contact resistances of each pair of phases; The degree quantization module is used to normalize the contact resistance of each phase and determine the degree of phase loss of the motor.

[0006] A computer-readable storage medium storing a computer program thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of an embodiment of a method for quantifying phase loss of each motor.

[0007] The aforementioned method for quantifying motor phase loss, motor drive device, and storage medium, by shutting off the bridge arm of the non-target phase, sequentially inputs DC voltage to the target phases between the three phase terminals of the motor, and samples the current of each target phase. The total resistance between each phase is determined based on the ratio of the DC voltage to the current of each target phase, and the sum of the contact resistances of the two phases is determined based on the difference between the total resistance between each phase and the stator resistance, thereby determining the contact resistance of each phase. After normalizing each contact resistance, the degree of phase loss of the motor can be determined. The degree of phase loss of the motor is quantified by contact impedance, realizing predictive maintenance and repair classification. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a flowchart illustrating a motor phase loss quantification method in one embodiment; Figure 2 This is a block diagram illustrating the principle of decoupling location and degree quantification of motor phase loss in one embodiment; Figure 3 This is the equivalent circuit diagram of the single-phase impedance and inter-phase impedance of the motor. Figure 4 This is a timing diagram of the voltage injection and current sampling process in one embodiment; Figure 5 This is a schematic diagram of the phase loss level graded response in one embodiment. Detailed Implementation

[0010] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0011] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0012] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly. The connection can be a direct connection or an indirect connection.

[0013] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0014] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0015] It is understood that the "data acquisition" operation in the embodiments of this application includes, but is not limited to, the following implementation methods: directly reading data pre-stored in the device; data received from external devices; or indirect acquisition methods after data collection, conversion and processing.

[0016] The motor phase loss quantification method provided in this application can be applied to, for example... Figure 1 In the application environment. Figure 1 This diagram illustrates the application environment of a motor phase loss quantification method in one embodiment. The terminal device can be, but is not limited to, various personal computers, laptops, smartphones, tablets, and portable wearable devices. The server can be a standalone server or a server cluster consisting of multiple servers.

[0017] In some embodiments, traditional passive phase loss detection methods rely on the motor's operating current signal. When the motor is stationary (before startup) or operating at low speed, the current signal is missing or has an extremely low signal-to-noise ratio, making phase loss detection impossible. However, the period before startup is precisely the most critical time for phase loss diagnosis—starting with a missing phase will cause serious consequences such as stalling and burnout. Another method uses "whether the current is zero" as a criterion, which can only distinguish between "conducting" and "disconnecting" states. For a gradually changing contact failure process where the contact impedance increases from mΩ to Ω, any non-zero current is considered "conducting," leading to the underreporting of moderate contact failures and hindering predictive maintenance and repair grading.

[0018] therefore Figure 1 A method for quantifying motor phase loss is provided, and its application to a motor drive device is illustrated using this method as an example. In this embodiment, the motor drive device broadly refers to a power electronic device with multi-phase power conversion bridge arms and phase current sampling capabilities, including but not limited to industrial frequency converters, servo drives, new energy electric drive inverters, and home appliance frequency converters. Figure 1 The diagram shown is a flowchart of a motor phase loss quantification method in one embodiment, including steps 102 to 110, wherein: Step 102: Turn off the bridge arm of the non-target phase, sequentially input DC voltage to the target phases of the three-phase terminals of the motor, and sample the current of each target phase.

[0019] This embodiment is applicable not only to permanent magnet synchronous motors, but also to asynchronous motors, brushless DC motors, and all other motors powered by inverters and equipped with Y-connected (or equivalently, phase-to-phase series measurement) windings for phase loss / poor contact detection. Application areas include frequency converters, servo motors, home appliances (air conditioner compressors), and electric drives for new energy vehicles. The motor refers to a three-phase motor, with the three phase terminals being U-phase, V-phase, and W-phase. Therefore, the target phase-to-phase currents are UV-phase, UW-phase, and VW-phase. The target phase current is the response current when the target phase-to-phase input is applied.

[0020] Specifically, when the motor is stationary or running at low speed, the three-phase half-bridge arms of the original three-phase inverter are reused as the injection source, and the original current sampling is used for response detection. For example, the motor drive device controls the inverter to turn off the upper and lower bridge arms of phase U, applies a DC voltage between the target phases V and W, and samples the response current of phases V and W; turns off the upper and lower bridge arms of phase V, applies a DC voltage between the target phases U and W, and samples the response current of phases U and W; turns off the upper and lower bridge arms of phase W, applies a DC voltage between the target phases U and V, and samples the response current of phases UV; the order of turn-off is not restricted.

[0021] Step 104: Determine the total resistance between each phase based on the ratio of the DC voltage to the current of each target phase.

[0022] The total phase-to-phase resistance includes the corresponding two-phase contact resistance and stator resistance. The contact resistance reflects the quality of the motor connection and can be used to quantify phase loss in the motor.

[0023] Specifically, the motor drive determines the total resistance between each phase based on the ratio of the DC voltage to the current of each target phase. For example, the total resistance between phases UV, R_total_uv = Ud / I_sample_uv, where Ud is the DC voltage and I_sample_uv is the target phase current. Similarly, the total resistances between phases, R_total_uw and R_total_vw, can be obtained.

[0024] Step 106: Determine the sum of the contact resistances of each pair of phases based on the difference between the total resistance between each phase and the stator resistance.

[0025] Among them, phase contact resistance includes U-phase contact resistance, V-phase contact resistance, and W-phase contact resistance. The sum of two-phase contact resistance is the sum of U-phase contact resistance and V-phase contact resistance.

[0026] Specifically, it is necessary to separate the sum of the contact resistances of the corresponding two phases from the total phase-to-phase resistance, where the stator resistance is known.

[0027] Therefore, the contact resistance of phase U is Rc_U, phase V is Rc_V, and phase W is Rc_W. The sum of the contact resistances of each pair of phases is determined by the difference between the total resistance between each phase and the stator resistance. For example, ΔUV represents the sum of the contact resistances of phase U and phase V, ΔVW represents the sum of the contact resistances of phase V and phase W, and ΔWU represents the sum of the contact resistances of phase W and phase U. Rs is the stator resistance. Then, we have...

[0028] Step 108: Determine the contact resistance of each phase based on the sum of the contact resistances of each pair of phases.

[0029] Specifically, the contact resistances Rc_U, Rc_V, and Rc_W of each phase are determined by deriving and calculating based on the above formulas ①, ②, and ③.

[0030] Step 110: Normalize the contact resistance of each phase to determine the degree of phase loss in the motor.

[0031] Specifically, the contact resistance of each phase can be normalized by the ratio of the contact resistance of each phase to the upper limit threshold of the degree of phase loss, thereby determining the degree of phase loss of the motor. The lower the normalized value, the less severe the phase loss; the higher the normalized value, the more severe the phase loss. It can be divided into five levels: normal, mild, moderate, severe, and complete, and the gradual change process of contact impedance from mΩ to Ω can be identified and graded.

[0032] Optionally, the phase of the missing phase can be determined based on the total phase-to-phase resistance. For example, by comparing the total phase-to-phase resistances R_total_UV, R_total_VW, and R_total_WU of the three pairs, if one pair is normal and two pairs are increasing, the normal pair does not contain a third phase fault; if all three pairs are normal, there is no fault; if all three pairs are increasing, there is a three-phase fault; if two pairs are normal and one pair is increasing, it is logically impossible to implement.

[0033] Optionally, the phase of the missing phase can be determined based on the relative ratios between the contact resistances of each phase. If the ratios of all three phases are close to 1, then the three phases are considered balanced and without fault; if a single phase is abnormally prominent and a certain ratio is large, then the phase with the largest contact resistance is missing; if two phases are similar and the third phase is extremely small, then those two phases are faulty.

[0034] In this embodiment, by shutting off the bridge arms of non-target phases, DC voltage is sequentially input to the target phases of the three-phase terminals of the motor, and the current of each target phase is sampled. The total resistance between each phase is determined based on the ratio of the DC voltage to the current of each target phase, and the sum of the contact resistances of two phases is determined based on the difference between the total resistance between each phase and the stator resistance, thereby determining the contact resistance of each phase. After normalizing each contact resistance, the degree of phase loss of the motor can be determined. The degree of phase loss of the motor is quantified by contact impedance, realizing predictive maintenance and repair classification. Moreover, detection can be actively injected when the motor is stationary or at low speed (before startup), covering the most critical time before startup, avoiding stalling and burnout caused by starting with a phase loss. In addition, the three-phase half-bridge arms and current sampling of the original three-phase inverter can be reused without adding any hardware, reducing costs.

[0035] In some embodiments, DC voltages are sequentially input to the target phases of the three-phase terminals of the motor, and the current of each target phase is sampled, including: The DC voltage is sequentially output to the target phases of the three-phase terminals of the motor, where the q-axis voltage is zero and the d-axis voltage increases from zero. During the d-axis voltage increase process, the target phase current is monitored in real time; When the target phase current reaches the preset current limit or the d-axis voltage reaches the preset voltage limit, sample the current of each target phase.

[0036] The preset current limit In is not limited to the rated current. It can be set to 0.3·In, 0.5·In, or according to the short-time thermal allowable current of the motor, to adapt to different heating constraint scenarios.

[0037] The preset voltage limit Ud_ref_max is not limited to Vbus·√3 / 3·0.5. It can be adjusted to other ratios of Vbus·√3 / 3 (such as 0.3, 0.6) according to the motor parameters and application scenarios, or the upper limit of the injection voltage can be directly calculated by back-calculating In and the estimated impedance.

[0038] Specifically, the q-axis voltage is 0, and the d-axis voltage increases from zero. Taking the upper and lower bridge arms of phase W as closed, with the target phases being phases U and V, as an example, the current flows only through the UV phases of the motor, Uq = 0. Ud increases slowly from zero using a ramp function, reaching a maximum of the preset voltage limit Ud_ref_max. During the d-axis voltage increase, the target phase current is monitored in real time. When the target phase current reaches the preset current limit, or the d-axis voltage reaches the preset voltage limit, the current DC voltage remains unchanged, and the target phase currents are sampled, namely the response currents of phases UV, UW, and VW.

[0039] Optionally, the rise of the d-axis voltage Ud is not limited to the ramp function. It can be achieved by step injection followed by limiting, exponential rise, lookup table method, or prediction adjustment based on the first trial, as long as the target phase current does not exceed the preset current limit In and the signal-to-noise ratio is sufficient.

[0040] In this embodiment, the q-axis voltage is zero to ensure that the motor has no torque and remains stationary, thus achieving static state detection and eliminating interference from the rotating magnetic field and inductor voltage drop. DC voltages are sequentially output to the target phases of the motor's three-phase terminals, where the q-axis voltage is zero and the d-axis voltage increases from zero. During this process, the target phase current is monitored in real time. When the current limit or voltage limit is reached, the target phase current is sampled, enabling real-time monitoring and dynamic cutoff of the target phase current to avoid surge impacts caused by step voltage and protect the motor.

[0041] In some embodiments, the preset current limit is the rated current of the motor; the preset voltage limit is half of the maximum available voltage.

[0042] Specifically, the preset current limit is the motor's rated current In, and the preset voltage limit Ud_ref_max is half of the maximum usable voltage.

[0043] Where Vbus is the bus voltage. Since the maximum usable voltage is ud, the maximum amplitude of the applied voltage is half of the usable voltage. Specifically, in the inverter's space vector modulation (SVPWM), the maximum lossless voltage amplitude that the DC bus voltage Vbus can synthesize is... .

[0044] In this embodiment, the preset current limit is the rated current of the motor, and the preset voltage limit is half of the maximum usable voltage. By limiting the magnitude of the current and voltage, it is possible to avoid excessive current passing through the motor, which could damage the motor.

[0045] In some embodiments, sampling to obtain the target phase current includes: during the DC voltage holding phase, continuously sampling the current and performing digital filtering to obtain the target phase current.

[0046] Specifically, during the DC voltage holding phase, the motor drive device samples the current for a certain period of time, filters it, and calculates its absolute value to obtain the target phase currents I_sample_uv, I_sample_uw, and I_sample_vw.

[0047] Optionally, current sampling noise reduction is not limited to mean filtering; digital filtering methods such as median filtering, moving average, and FIR (Finite Impulse Response Filter) can be used.

[0048] In this embodiment, during the DC voltage holding phase, the current is continuously sampled and digitally filtered to obtain the target phase current, which can reduce sampling noise interference.

[0049] In some embodiments, determining the sum of the contact resistances of each pair of phases based on the difference between the total interphase resistance and the stator resistance includes: The sum of the contact resistances of the corresponding two phases is determined by the difference between the total resistance between each phase and twice the stator resistance.

[0050] Specifically, the contact resistance of phase U is Rc_U, the contact resistance of phase V is Rc_V, and the contact resistance of phase W is Rc_W. The sum of the contact resistances of each pair of phases is determined by the difference between the total resistance between each phase and the stator resistance. For example, ΔUV represents the sum of the contact resistances of phase U and phase V, ΔVW represents the sum of the contact resistances of phase V and phase W, and ΔWU represents the sum of the contact resistances of phase W and phase U. Then we have...

[0051] The total resistance between each phase is known, and the stator resistance is also known. Therefore, the sum of the contact resistances between the two phases can be obtained.

[0052] In this embodiment, the sum of the contact resistances of the two phases is determined based on the difference between the total phase-to-phase resistance and twice the stator resistance, thus enabling the separation of the sum of the contact resistances of the two phases from the total phase-to-phase resistance.

[0053] In some embodiments, determining the contact resistance of each phase based on the sum of the contact resistances of each pair of phases includes: For any phase, add the sum of the contact resistances of the two phases containing the phase, subtract the sum of the contact resistances of the two phases not containing the phase, and take half of the result as the phase contact resistance of the phase.

[0054] Specifically, by analyzing equations ①, ②, and ③, adding the three equations together yields: (Rc_U + Rc_V) + (Rc_V + Rc_W) + (Rc_W + Rc_U) = ΔUV + ΔVW + ΔWU 2·(Rc_U + Rc_V + Rc_W) = ΔUV + ΔVW + ΔWU Let the sum of the three phases be S = Rc_U + Rc_V + Rc_W, then: S = (ΔUV + ΔVW + ΔWU) / 2 Therefore, the contact resistance of phase W, Rc_W = S - ΔUV = (ΔUV + ΔVW + ΔWU) / 2 - ΔUV = (ΔUV + ΔVW + ΔWU - 2·ΔUV) / 2 = (ΔVW + ΔWU - ΔUV) / 2 That is, the sum of the contact resistances of the two phases containing phase W, ΔVW and ΔWU, is added together, and the sum of the contact resistances of the two phases excluding phase W, ΔUV, is subtracted. Half of the result is taken as the phase contact resistance of phase W.

[0055] Similarly, the contact resistance of phase U is Rc_U = S - (Rc_V + Rc_W) = S - ΔVW = (ΔUV + ΔVW + ΔWU) / 2 - ΔVW = (ΔUV + ΔWU - ΔVW) / 2 Phase V contact resistance Rc_V = S - (Rc_U + Rc_W) = S - ΔWU = (ΔUV + ΔVW + ΔWU) / 2 - ΔWU = (ΔUV + ΔVW - ΔWU) / 2 Specifically, for any phase, the sum of the two phase resistances containing that phase is subtracted from the sum of the contact resistances of the two phases excluding that phase, and half of the result is taken as the phase contact resistance of that phase. This allows us to obtain the contact resistance of each phase and quantify the phase loss of the motor.

[0056] In some embodiments, normalizing the contact resistance of each phase to determine the degree of phase loss in the motor includes: The degree index is obtained by comparing the ratio between the contact resistance of each phase and the upper limit threshold of degree quantification. The degree of phase loss of the motor is determined based on the range of values ​​that the degree index falls into.

[0057] The upper limit threshold R_max of the degree quantization corresponds to the equivalent complete disconnection. Equivalent complete disconnection includes situations such as torque pulsation, vibration, and heat generation reaching unacceptable levels, contact resistance reaching X times the stator resistance, and severe copper loss distribution. Therefore, the degree of phase loss of the motor can be determined by using the upper limit threshold of the degree quantization.

[0058] Specifically, the degree index D_X = clamp( Rc_X / R_max, 0, 1.0 ), X ∈ {U, V, W} That is, D=0 when Rc_X< 0, D=1.0 when Rc_X>R_max, otherwise D = Rc_X / R_max. D is a continuous value from 0 to 1, reflecting the normalization degree of the contact impedance relative to "complete disconnection".

[0059] The motor drive device determines the phase loss degree of the motor according to the numerical range into which the degree index falls, so as to perform response control on the motor according to the phase loss degree of the motor. The numerical range such as (0.05 / 0.3 / 0.7 / 1.0) can be adjusted according to the motor capacity and application scenario; the graded response actions (allowing operation / warning / derating / shutdown) can be configured according to system requirements.

[0060] In this embodiment, the degree index is obtained according to the ratio between the contact resistance of each phase and the upper quantization threshold of the degree, and the phase loss degree of the motor is determined according to the numerical range into which the degree index falls, so that the response mode for the motor can be determined, and damage to the motor can be avoided.

[0061] In some embodiments, the motor phase loss quantification method further comprises: determining the phase with phase loss according to the comparison result between the contact resistance of each phase and the phase loss judgment threshold.

[0062] The phase loss judgment threshold R_thresh is set according to requirements and stored in the motor drive device.

[0063] Specifically, the motor drive device determines the phase with phase loss according to the comparison result between the contact resistance of each phase and the phase loss judgment threshold, as follows: If Rc_U>R_thresh and Rc_V, Rc_W<R_thresh → U phase poor contact / phase loss If Rc_V>R_thresh and the rest are normal → V phase poor contact / phase loss If Rc_W>R_thresh and the rest are normal → W phase poor contact / phase loss If two phases are simultaneously >R_thresh → two-phase phase loss (simultaneous cable fault) If three phases are simultaneously >R_thresh → three-phase disconnection or neutral point disconnection Note: R_thresh is the judgment threshold for phase loss, and when the contact resistance is greater than this value, a phase loss is determined. In this embodiment, the phase with phase loss can be determined accurately and at low cost according to the comparison result between the contact resistance of each phase and the phase loss judgment threshold.

[0064] In some embodiments, Figure 2 is a schematic block diagram of the decoupling positioning and degree quantification of motor phase loss in one embodiment, which is applied to an inverter or a driver, including an MCU (software) side and a hardware execution side. The inverter / driver is represented by a dashed box as a whole, the functional modules implemented by MCU software are inside, and the inverter bridge and the motor body are outside.

[0065] The MCU-side "Voltage Injection Command Generation (Ud Ramp)" module generates a d-axis voltage ramp command, while the q-axis voltage remains zero. This command is sent to the "PWM Modulation (Shut Down a Certain Phase Arm)" module, which generates a PWM drive signal with a specific timing, and outputs it to the inverter bridge U / V / W. The inverter bridge shuts down the upper and lower arms of the non-target phase according to the PWM command, and outputs a DC voltage vector to the target two phases, which is applied to the motor's U / V / W three-phase terminals.

[0066] The motor phase current is acquired by the current sampling module, and then subjected to mean filtering and absolute value calculation. The filtered current and the injected voltage command are used to calculate the phase-total resistance R_total = Ud / I_sample, thus obtaining the total phase-total resistance. The three pairs of phase-total resistances are decoupled and used to calculate the Rc of each phase (full-rank equation). By constructing and solving the full-rank linear equation system, the independent contact impedances Rc_U, Rc_V, and Rc_W of each phase are obtained. Subsequently, the degree quantization D = Rc / Rmax is calculated, and the contact impedance is normalized to the continuity index D and graded according to a preset threshold. Finally, the phase loss location and phase loss degree are output, including the fault phase identifier and the corresponding warning code W01, W02 or fault code F01.

[0067] Figure 2 The functional modules are located on the MCU (software) side, while the inverter bridge U / V / W and motor U / V / W are existing hardware. This system reuses the three-phase half-bridge arms of the original three-phase inverter as the voltage injection source and the existing current sampling as the response detection. Phase loss diagnosis is implemented purely in software without adding any hardware components.

[0068] Motor static impedance model Figure 3 This is the equivalent circuit diagram of the single-phase impedance and phase-to-phase impedance of the motor. Figure 3 Divided into two parts, the left side is the single-phase impedance model and the right side is the phase-to-phase impedance (Y-connected, two phases in series) model, which together illustrate the simplified principle of motor impedance under DC injection conditions and the physical basis of phase-to-phase measurement in this invention.

[0069] Left side: Single-phase impedance module The equivalent circuit of any phase of the motor (taking phase U as an example) is shown. From terminal U to neutral point N, the stator resistance Rs and contact impedance Rc are connected in series. When the motor is stationary, there is no back electromotive force (e=0). The equivalent circuit for each phase is the stator resistance Rs and leakage inductance Lsσ connected in series, followed by the contact impedance Rc for that phase. The impedance of each phase is: Z_phase(f) = Rs + Rc + j•ω•Lsσ, where ω = 2π•f and j is the imaginary unit.

[0070] Where Rs is the stator resistance (a known quantity, identified from the nameplate or during startup, or obtained in conjunction with other solutions), Lsσ is the stator leakage inductance, and Rc is the contact impedance of that phase (reflecting faults: Rc≈0 in normal state, gradually increases during the initiation period, and Rc→∞ when completely disconnected).

[0071] With DC injection, the complex impedance term caused by the inductance disappears, and the single-phase impedance degenerates into pure resistance, providing a physical basis for subsequent real-number calculations. The formula can be simplified to... ω=0 →jωL=0 →Z_phase ≈ Rs + Rc Right side: Phase-to-phase impedance (Y-connected, two phases in series) model For a Y-connected motor with no external neutral point N (a typical connection for inverter-powered motors), the current path during phase-to-phase injection is a series circuit formed by connecting the U-phase winding, the internal neutral point N, and the V-phase winding. The phase-to-phase impedance is the sum of the impedances of the two phases. Because the injected voltage is a DC voltage, the impedance caused by inductance can be ignored.

[0072] The total interphase resistance Z_UV(f) = Z_U + Z_V = (2•Rs + Rc_U + Rc_V) The total interphase resistance Z_VW(f) = Z_V + Z_W = (2•Rs + Rc_V + Rc_W) The total interphase resistance Z_WU(f) = Z_W + Z_U = (2•Rs + Rc_W + Rc_U) Let the resistance part be R_total_XY = 2•Rs + Rc_X + Rc_Y (XY represents phase-to-phase, such as UV, VW, WU).

[0073] Key observation (physical basis of three-phase decoupling location): When the contact impedance Rc_X of a certain phase abnormally increases, the inter-phase impedances of the two phases containing that phase also increase, while the inter-phase impedance of the phase not containing that phase remains normal. For example, when phase U is abnormal: Z_UV increases (containing U), Z_WU increases (containing U), and Z_VW remains normal (excluding U). Based on this, phase loss location can be achieved.

[0074] Injected voltage and current sampling When measuring the resistance between the UV phases, the upper and lower bridge arms of the W phase need to be turned off so that the motor current flows only between the UV phases. Similarly, when measuring the UW phase, the V phase needs to be turned off, and when testing the VW phase, the U phase needs to be turned off.

[0075] When measuring the resistance between the UV phases, the angle of the voltage vector is 0°.

[0076] When measuring the resistance between phases V and W, the angle of the voltage vector is: .

[0077] When measuring the resistance between phases U and W, the angle of the voltage vector is: .

[0078] The injected voltage is applied to the D-axis voltage of the rotating coordinate system. If the applied voltage is too large, it will cause excessive motor current, damaging the motor. If the applied current is too small, it will result in insufficient sampled phase current, a low signal-to-noise ratio, and affect resistance calculations. Therefore, the maximum amplitude of the applied voltage is...

[0079] Where Vbus is the bus voltage. Since ud is the maximum voltage available, the maximum amplitude of the applied voltage is half of the available voltage.

[0080] In order to prevent motor overcurrent, the phase current of the motor is also limited, and the limit of the phase current is the rated current In of the motor.

[0081] Taking the UV phase as an example, the voltage injection process first turns off the upper and lower bridge arms of the W phase to ensure that the current flows only through the UV phase of the motor. Uq=0, Ud is slowly increased from zero using a ramp function, up to a maximum of Ud_ref_max. While the voltage is gradually increasing, the phase current of the motor is detected. If the absolute value of the phase current is greater than the current limit value In or Ud=Ud_ref_max, the current injection voltage is kept unchanged, and the process proceeds to the next step of current sampling.

[0082] To reduce sampling noise, the UV phase current is sampled continuously for a certain time period, then mean filtered and the absolute value is calculated to obtain I_sample_uv. Similarly, I_sample_uw and I_sample_vw can be obtained.

[0083] like Figure 4 The figure shown is a timing diagram of the voltage injection and current sampling process in one embodiment. Figure 4 Divided into two sub-plots, the diagram shows the time-series relationship between Ud (injected voltage) and phase current, presenting the complete process of a single phase-to-phase injection: the voltage injection phase (ramp-up) and the current sampling phase (holding Ud, mean filtering). The upper sub-plot shows the voltage injection phase (ramp-up) where Uq=0 and the Ud ramp-up slowly increases from zero. Ud increases linearly over time until it reaches Ud_ref_max = Vbus·√3 / 3·0.5, at which point sampling begins. Afterward, the injected voltage remains constant, transitioning to the current sampling phase (holding Ud, mean filtering).

[0084] The lower sub-diagram illustrates the phase current monitoring: a dual-condition limiting mechanism that maintains the injected voltage when |I|>In or Ud=Ud_ref_max. During the voltage injection phase, the phase current |I| rises synchronously with Ud. When |I| reaches the current limit In (shown as a dashed line in the diagram, with the annotation that |I|>In maintains the voltage), the holding condition is triggered synchronously with Ud reaching Ud_ref_max, and the injected voltage enters a constant phase. Subsequently, the phase current is continuously sampled using green discrete sampling points, and a stable current measurement value is obtained after mean filtering, which is used for subsequent inter-phase resistance calculations. The two sub-diagrams achieve timing alignment, demonstrating the complete closed-loop process of voltage ramp, current monitoring, condition triggering, and sample-and-hold.

[0085] The phase-total resistance R_total_uv is calculated as follows: R_total_uv = Ud / I_sample_uv; Similarly, we can obtain R_total_uw and R_total_vw. Separate the contact resistance Rc from R_total: Given Rs, subtract pairswise:

[0086] Adding the three equations together, we get: (Rc_U + Rc_V) + (Rc_V + Rc_W) + (Rc_W + Rc_U) = ΔUV + ΔVW + ΔWU 2·(Rc_U + Rc_V + Rc_W) = ΔUV + ΔVW + ΔWU Let the sum of the three phases be S = Rc_U + Rc_V + Rc_W, then: S = (ΔUV + ΔVW + ΔWU) / 2 Find Rc_W (subtract equation ① from the sum S): Rc_W = S - ΔUV = (ΔUV + ΔVW + ΔWU) / 2 - ΔUV = (ΔUV + ΔVW + ΔWU - 2·ΔUV) / 2 = (ΔVW + ΔWU - ΔUV) / 2 Similarly Rc_U = S - (Rc_V + Rc_W) = S - ΔVW = (ΔUV + ΔVW + ΔWU) / 2 - ΔVW = (ΔUV + ΔWU - ΔVW) / 2 Rc_V = S - (Rc_U + Rc_W) = S - ΔWU = (ΔUV + ΔVW + ΔWU) / 2 - ΔWU = (ΔUV + ΔVW - ΔWU) / 2 Phase loss positioning decision logic One phase is abnormal → two pairs of phase-to-phase impedances including this phase increase simultaneously, and the one pair not including this phase is normal If Rc_U>R_thresh and Rc_V, Rc_W<R_thresh → U phase poor contact / phase loss If Rc_V>R_thresh and the rest are normal → V phase poor contact / phase loss If Rc_W>R_thresh and the rest are normal → W phase poor contact / phase loss If two phases are simultaneously >R_thresh → two-phase loss (simultaneous cable fault) If three phases are simultaneously >R_thresh → three-phase disconnection or neutral point disconnection Note: R_thresh is the judgment threshold for phase loss, and phase loss is judged when the contact resistance is greater than this value Numerical verification example Assume the actual Rc_U = 4Ω, Rc_V = 0Ω, Rc_W = 0Ω (moderate poor contact of U phase), then: ΔUV = Rc_U + Rc_V = 4 + 0 = 4 ΔVW = Rc_V + Rc_W = 0 + 0 = 0 ΔWU = Rc_W + Rc_U = 0 + 4 = 4 Substitute into the closed-form solution:

[0087] Perfect restoration. It can be seen that when the U phase is abnormal, the two pairs ΔUV and ΔWU including U both increase (=4), and ΔVW not including U is normal.

[0088] Phase loss degree quantification (continuous index D) Assume R_max is the upper limit threshold for degree quantification (corresponding to "equivalent complete disconnection", for example, R_max = 10Ω or 5•Rs), and normalize the contact impedance of each phase into a continuous degree index: D_X = clamp( Rc_X / R_max, 0, 1.0 ), X ∈ {U, V, W} That is, D=0 when Rc_X< 0, D=1.0 when Rc_X>R_max, otherwise D = Rc_X / R_max. D is a continuous value from 0 to 1, reflecting the normalization degree of the contact impedance relative to "complete disconnection" - this is the core quantitative innovation that surpasses the "on / off binary" of the comparison scheme.

[0089] Figure 5 This is a schematic diagram of the phase loss level graded response in one embodiment. Figure 5 The graph uses D as the horizontal axis to show the complete range division of the quantitative graded response to phase loss and the corresponding control strategy. The contact impedance Rc_X of each phase is normalized to a continuity index of 0 to 1.

[0090] Figure 5 The corresponding classification and response are shown in Table 1:

[0091] Table 1 The engineering value of quantification: Traditional methods only have two values, on / off. When D=0.5 (moderate poor contact), the comparison scheme judges it as "on" (current is not zero) and misses the report. This embodiment reports "moderate poor contact" and reduces the rating; the upward trend of D over time can predict the remaining life (in conjunction with passive prediction scheme); D distinguishes between "tightening the terminal" (mild) and "replacing the cable" (severe), guiding the maintenance level.

[0092] This embodiment has the following beneficial effects: Advantage 1 (Criterion): Quantitative comparison of continuity level between on / off values. This embodiment uses contact impedance normalization to obtain a continuity index D (D=Rc / R_max), divided into five levels: normal / mild / moderate / severe / complete. It can identify the gradual change process of contact impedance from mΩ to Ω and respond in stages. The comparison scheme only uses the "whether the current is zero" on / off value, which misses the report for moderate contact failures. This invention achieves predictive maintenance and repair classification.

[0093] Advantage 2 (Operating Condition Coverage): Detectable in a stationary state. This invention can actively inject detection when the motor is stationary (before startup), covering the most critical time before startup and avoiding stalling and burnout caused by starting with a missing phase; passive detection technology cannot detect when there is no current signal in a stationary state.

[0094] Advantage 3 (Cost): Zero hardware increment. This invention reuses the three-phase half-bridge arms and current sampling of the original three-phase inverter, implemented purely in software, without adding any hardware, reducing costs and facilitating upgrades to existing products.

[0095] Advantage 4 (Efficiency): Rapid completion of a single injection. This invention uses Ud ramp injection combined with mean filtering, and three pairs of measurements can be completed within seconds without affecting the startup experience. This is shorter than the two-step serial process of the comparison scheme.

[0096] Advantage 5 (Safety): Dual-condition injection protection. The injection process is subject to dual constraints of the phase current limit In and the upper limit of the injection voltage Ud_ref_max, which avoids overcurrent damage to the motor and ensures injection safety.

[0097] In one embodiment, a method for quantifying a phase loss in a motor includes: Step (a1) sequentially outputs DC voltage between the target phases of the three-phase terminals of the motor, wherein the q-axis voltage is zero and the d-axis voltage increases from zero.

[0098] Step (a2): During the d-axis voltage increase process, monitor the target phase current in real time.

[0099] Step (a3): When the target phase current reaches the preset current limit or the d-axis voltage reaches the preset voltage limit, during the DC voltage holding phase, the current is continuously sampled and digitally filtered to obtain the current of each target phase; the preset current limit is the rated current of the motor; the preset voltage limit is half of the maximum usable voltage.

[0100] Step (a4): Determine the total resistance between each phase based on the ratio of the DC voltage to the current of each target phase.

[0101] Step (a5): Determine the sum of the contact resistances of the corresponding two phases based on the difference between the total resistance between each phase and twice the stator resistance.

[0102] Step (a6): For any phase, add the sum of the contact resistances of the two phases containing the phase, subtract the sum of the contact resistances of the two phases not containing the phase, and take half of the result as the phase contact resistance of the phase.

[0103] Step (a7): Determine the phase of the missing phase based on the comparison results between the contact resistance of each phase and the phase loss judgment threshold.

[0104] Step (a8): Obtain the degree index based on the ratio between the contact resistance of each phase and the degree quantification upper limit threshold.

[0105] Step (a9): Determine the degree of phase loss of the motor based on the numerical range of the degree index.

[0106] In this embodiment, by turning off the bridge arms of non-target phases, DC voltage is sequentially input to the target phases of the three-phase terminals of the motor, and the current of each target phase is sampled. The total resistance between each phase is determined according to the ratio of the DC voltage to the current of each target phase, and the sum of the contact resistances of two phases is determined according to the difference between the total resistance between each phase and the stator resistance, thereby determining the contact resistance of each phase. After normalizing each contact resistance, the degree of phase loss of the motor can be determined. The degree of phase loss of the motor is quantified by the contact impedance, realizing predictive maintenance and repair classification. Moreover, detection can be actively injected when the motor is stationary (before starting), covering the most critical time before starting, avoiding stalling and burnout caused by starting with a phase loss. In addition, the three-phase half-bridge arms and current sampling of the original three-phase inverter can be reused without adding any hardware, reducing costs.

[0107] It should be understood that, although the above Figure 1 In the flowchart, the steps are shown sequentially according to the arrows, and the steps (a1) to (a9) are shown sequentially according to their numbers. However, these steps are not necessarily executed in the order indicated by the arrows or numbers. Unless explicitly stated herein, there is no strict order requirement for the execution of these steps; they can be executed in other orders. Figure 1 At least some of the steps in the process may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0108] In some embodiments, a motor drive device is provided, which may be a software module, a hardware module, or a combination of both as part of a computer device. Specifically, the device includes: a voltage injection module, a current sampling module, a resistance determination module, and a level quantization module, wherein: The voltage injection module is used to turn off the bridge arm of the non-target phase and sequentially input DC voltage to the target phases of the three-phase terminals of the motor. The current sampling module is used to sample and obtain the current of each target phase. The resistance determination module is used for: The total resistance between each phase is determined by the ratio of the DC voltage to the current of each target phase. The sum of the contact resistances between each pair of phases is determined based on the difference between the total resistance between each phase and the stator resistance. The contact resistance of each phase is determined by the sum of the contact resistances of each pair of phases; The degree quantization module is used to normalize the contact resistance of each phase to determine the degree of phase loss of the motor.

[0109] Specific limitations regarding the motor drive device can be found in the above section on the limitations of the motor phase loss quantification method, and will not be repeated here. Each module in the aforementioned motor drive device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0110] In some embodiments, a motor drive device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method embodiments.

[0111] In some embodiments, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method embodiments.

[0112] In some embodiments, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the above-described method embodiments.

[0113] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0114] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for quantifying phase loss in a motor, characterized in that, The method includes: Turn off the bridge arm of the non-target phase, sequentially input DC voltage to the target phases of the three-phase terminals of the motor, and sample to obtain the current of each target phase; The total resistance between each phase is determined based on the ratio of the DC voltage to the current of each target phase. The sum of the contact resistances of each pair of phases is determined based on the difference between the total resistance between each phase and the stator resistance. The contact resistance of each phase is determined based on the sum of the contact resistances of each pair of phases; The phase loss degree of the motor is determined by normalizing the contact resistance of each phase.

2. The method according to claim 1, characterized in that, The process of sequentially inputting DC voltages to the target phases of the motor's three-phase terminals and sampling the current of each target phase includes: The DC voltage is sequentially output to the target phases of the three-phase terminals of the motor, where the q-axis voltage is zero and the d-axis voltage increases from zero. During the d-axis voltage increase process, the target phase current is monitored in real time; When the target phase current reaches the preset current limit or the d-axis voltage reaches the preset voltage limit, the target phase current is sampled and obtained.

3. The method according to claim 2, characterized in that, The preset current limit is the rated current of the motor; the preset voltage limit is half of the maximum usable voltage.

4. The method according to claim 1, characterized in that, The sampling to obtain the target phase current includes: During the DC voltage holding phase, the current is continuously sampled and digitally filtered to obtain the target phase current.

5. The method according to claim 1, characterized in that, The step of determining the sum of the contact resistances of each pair of phases based on the difference between the total resistance between each phase and the stator resistance includes: The sum of the contact resistances of the corresponding two phases is determined based on the difference between the total resistance between each phase and twice the stator resistance.

6. The method according to claim 1, characterized in that, The step of determining the contact resistance of each phase based on the sum of the contact resistances of each pair of phases includes: For any phase, add the sum of the contact resistances of the two phases containing the phase, subtract the sum of the contact resistances of the two phases excluding the phase, and take half of the result as the phase contact resistance of the phase.

7. The method according to any one of claims 1 to 6, characterized in that, The step of normalizing the contact resistance of each phase to determine the degree of phase loss of the motor includes: The degree index is obtained by comparing the ratio between the contact resistance of each phase and the upper limit threshold of the degree quantification. The degree of phase loss of the motor is determined based on the numerical range within which the degree index falls.

8. The method according to any one of claims 1 to 6, characterized in that, The method further includes: The phase of the missing phase is determined by comparing the contact resistance of each phase with the phase loss judgment threshold.

9. A motor drive device, characterized in that, To implement the method according to any one of claims 1 to 8, comprising: The voltage injection module is used to turn off the bridge arm of the non-target phase and sequentially input DC voltage to the target phases of the three-phase terminals of the motor. The current sampling module is used to sample and obtain the current of each target phase. The resistance determination module is used for: The total resistance between each phase is determined based on the ratio of the DC voltage to the current of each target phase. The sum of the contact resistances of each pair of phases is determined based on the difference between the total resistance between each phase and the stator resistance. The contact resistance of each phase is determined based on the sum of the contact resistances of each pair of phases; The degree quantization module is used to normalize the contact resistance of each phase and determine the degree of phase loss of the motor.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 8.

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