Method for monitoring starter, starter and computer readable storage medium
By monitoring the starter, using the processor and electric motor thermal protection application, the limit theoretical thermal state and current thermal state of the electric motor are calculated, which solves the thermal failure problem during continuous start of the electric motor and improves the startup success rate and debugging efficiency.
Patent Information
- Application Number
- CN202510040410.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-02-12
- Filing Date
- 2025-01-10
- Publication Date
- 2025-08-12
AI Technical Summary
Prior art When the electric motor is continuously started, thermal protection applications cause frequent thermal failure trips, resulting in startup failure and may cause mechanical damage, and the waiting recovery time is not fixed, affecting debugging efficiency.
By monitoring the starter, using the processor and electric motor thermal protection application, the limit theoretical thermal state and current thermal state of the electric motor are calculated, the warning signal is sent to prevent thermal failure, the theoretical waiting time and possible start times are calculated, and the mathematical model based on standard IEC 60947 is protected.
Effectively prevent thermal failure of electric motors, reduce debugging time, improve startup success rate, reduce mechanical damage, and provide accurate waiting time and start-up times guidance.
Smart Images
Figure CN120474382A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to methods of monitoring starters, soft starters, and direct-on-line starters. Background Art
[0002] The user may need to perform several consecutive starts of the electric motor, for example when commissioning an installation or when there is a problem with the power grid.
[0003] Because the current level in the electric motor can be four times the nominal current, the electric motor preheats during the startup phase. To prevent the motor from overheating, a thermal probe can be installed on the electric motor. A thermal relay or software thermal protection application can also be installed on the starter.
[0004] Thermal protection applications are based on a theoretical mathematical model that represents the evolution of heat in electric motors. This theoretical model is defined by the standard known as "IEC 60947." This standard was established to protect motors from overheating.
[0005] When a thermal protection application is implemented on a starter and several consecutive starts of an electric motor are performed, the thermal protection application triggers a motor thermal fault, which prohibits further starts until the motor is deemed to be at an acceptable temperature according to IEC 60947. The user must then wait before initiating a new start. The length of this waiting period varies. It depends on factors such as the motor's protection rating, the motor's initial temperature, and the ambient temperature. If the user initiates a new start and the thermal protection application determines that the motor is overheated, the application generates a new motor thermal fault. In this case, the start fails, but the motor is reheated by the start of the new start, forcing the user to wait even longer before starting. Furthermore, such a start can cause mechanical damage to the motor.
[0006] It would be desirable to provide a service that warns the user that it is useless to initiate a new start, as such a new start would in any case result in a fault and would preheat the electric motor again. It would also be desirable to warn the user of the time he must wait before a new start can be initiated without generating a thermal fault. Finally, it would be desirable to inform the user of the number of consecutive starts he can perform before a thermal fault trips the system. Summary of the Invention
[0007] An object of the present disclosure is to propose a method of monitoring a starter to prevent the user from triggering a motor thermal fault before it occurs.
[0008] To achieve this objective, the present disclosure proposes a method for monitoring a starter, the starter being connected to an electrical grid and an electric motor; the electric motor having at least one winding; the starter comprising a processor and an electric motor thermal protection application, the electric motor thermal protection application being configured to cause a motor thermal fault trip when the electric motor reaches a defined thermal condition; the method comprising:
[0009] a) Initial start of the electric motor,
[0010] b) determining the duration of the first start and the current supplied to a winding of the electric motor during the on-state of the first start,
[0011] c) calculating a limiting theoretical thermal state of the electric motor based on the duration of the first start, the current supplied to one winding of the electric motor during the first start and the parameters of said electric motor,
[0012] d) determining the current supplied to a winding of an electric motor,
[0013] e) calculating a current thermal state based on the determined current and said electric motor parameters,
[0014] f) comparing the current thermal state with a limit theoretical thermal state, and sending a warning signal representing a risk of triggering a motor thermal failure if the current thermal state is greater than the limit theoretical thermal state.
[0015] Advantageously, the method relies on a motor thermal protection application based on standard IEC 60947.
[0016] This approach is very useful when the user is doing some testing while debugging the installation, as he has a realistic perspective of the time and number of starts he can make.
[0017] This is a feature that saves debugging time.
[0018] Optionally, the electric motor parameters include a nominal current of the electric motor, a time constant, and an error threshold of a thermal state of the electric motor.
[0019] Optionally, if the current thermal state is lower than the limit theoretical thermal state, steps d) to f) are repeated.
[0020] Optionally, the transmission of the warning signal blocks a command received by the starter to initiate the current start.
[0021] Optionally, the method includes calculating a theoretical waiting time based on a theoretical limit thermal state, a current thermal state and a time constant.
[0022] Optionally, the method includes displaying the theoretical waiting time on a display screen.
[0023] Optionally, the method includes displaying a countdown timer on the display screen, the countdown timer being configured to count down from the theoretical waiting time to zero.
[0024] Optionally, when the current thermal state is lower than the limit theoretical thermal state, the method comprises calculating, by the electric motor thermal protection application, a possible number of starts before a thermal fault trip of the electric motor, the possible number of starts being calculated based on the duration of the first start, based on the current supplied to one winding of the electric motor during the first start, based on the electric motor parameters and based on the limit thermal state calculated for n starts.
[0025] Optionally, the method includes displaying the number of possible starts on a display screen.
[0026] Optionally, if the starter has been switched off, the theoretical waiting time is recorded in the memory unit, the method comprising the calculation of the remaining waiting time when switching on the starter, the remaining waiting time taking into account the power-off time.
[0027] Optionally, the defined thermal condition causing the motor thermal fault trip is based on the thermal protection class of the motor, the nominal current of the motor and settings based on standard IEC 60947.
[0028] The present disclosure also provides a method for monitoring a starter, the starter being connected to an electrical grid and an electric motor; the electric motor having at least one winding; the starter comprising a processor and an electric motor thermal protection application, the electric motor thermal protection application being configured to cause a thermal fault trip of the electric motor when the electric motor reaches a defined thermal condition; the method comprising:
[0029] a) Start the electric motor,
[0030] b) determining the current supplied to a winding of the electric motor,
[0031] c) calculating the current thermal state based on the electric motor, the current determined during startup and parameters of said electric motor,
[0032] d) comparing the current thermal state to the first thermal state and, if the current thermal state is greater than the first thermal state, treating the current thermal state as the previous thermal state,
[0033] e) determining the current supplied to a winding of the electric motor,
[0034] f) calculating the current thermal state based on the electric motor, the current determined during starting and parameters of said electric motor,
[0035] g) comparing the current thermal state with the previous thermal state and sending a warning signal representing a risk of triggering a motor thermal failure if the current thermal state is greater than the previous thermal state.
[0036] The present disclosure also proposes a computer-readable storage medium comprising instructions, which, when executed by a processor, cause the processor to perform the method of any one of the above claims.
[0037] The present disclosure also proposes a starter comprising a processor including a storage unit storing electric motor parameters, the processor being adapted to implement the method according to any one of the preceding claims.
[0038] Optionally, the state machine is a soft starter or a direct on-line starter. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Figure 1 is a schematic diagram of an example of a circuit including a soft starter according to the present disclosure.
[0040] Figure 2 is a flow chart of a monitoring method according to the present disclosure.
[0041] Figure 3 An example of the warm-up process of an electric motor during six consecutive starts. DETAILED DESCRIPTION
[0042] The present disclosure applies to a method for monitoring a starter for starting an electric motor. Figure 1 An example of a circuit to which this method can be applied is shown.
[0043] Figure 1 The circuit includes a power grid 2 , an electric motor 4 connected to the power grid 2 , and a motor soft starter 6 connected between the power grid 2 and the electric motor 4 .
[0044] The electrical grid 2 is configured to supply power to the electric motor 4. Figure 1 In the embodiment, the electrical network 2 is a three-phase network designed to provide an electrical signal, such as an AC signal, in each winding of an electric motor. The electrical network 2 comprises three electrical network phases 8, 10 and 12, which are respectively connected to the arms of the motor soft starter.
[0045] The soft starter 6 comprises three arms 14 , 16 and 18 suitable for being connected respectively on one side to the three windings 20 , 22 , 24 of the electric motor 4 and on the other side to the three phases 8 , 10 and 12 of the electrical network.
[0046] Each arm 14, 16, 18 of the soft starter comprises two thyristors in an anti-parallel configuration (head-to-tail), as defined in IEC 61148. Figure 1 As shown. The arms 14, 16, 18 of the soft starter can be considered as controlled switches between the phases 8, 10, 12 of the power grid and the corresponding windings 20, 22, 24 of the electric motor. That is, by controlling the thyristors of the arms 14, 16, 18 of the soft starter, the electrical signals transmitted from the phases of the power grid to the corresponding windings of the electric motor can be controlled.
[0047] exist Figure 1 In the embodiment shown, the soft starter further comprises a current determination device 25 for measuring the instantaneous current in each arm of the starter. The instantaneous current determination device 25 is, for example, an ammeter.
[0048] Alternatively, the soft starter comprises an input unit capable of receiving a current value from an external current determination device configured to measure the instantaneous current in each phase of the electrical network or in each winding of the electric motor.
[0049] exist Figure 1 In the soft starter, the soft starter includes a processor 26, such as a controller or a microcontroller. The processor 26 can be configured to control the thyristors of each arm by controlling the supply of their respective gates with appropriate trigger pulses so that the thyristors can switch from a blocking state to a passing state.
[0050] The processor 26 is configured to operate according to the methods described herein.The processor 26 may include electronic circuitry for computing managed by an operating system.
[0051] The processor includes a timer 28 configured to measure the duration of motor activation.
[0052] The processor may include a countdown timer 29 .
[0053] The soft starter may also include a non-transitory machine-readable or computer-readable storage medium 30. The storage medium is encoded with instructions executable by a processor, such as processor 26, to perform the example methods described herein.
[0054] The computer readable storage unit 30 according to the present disclosure can be any electronic, magnetic, optical or other physical storage device that stores executable instructions. The computer readable storage unit can be, for example, a random access memory (RAM), an electrically erasable programmable read-only memory (EEPROM), a storage drive, an optical disk, etc.
[0055] Computer-readable storage unit 30 may be encoded with an electric motor thermal protection application 32. The electric motor thermal protection application 32 is configured, when executed by a processor, to cause a trip of an electric motor thermal fault when the electric motor is within defined conditions. The motor thermal protection application 32 contains executable instructions. The purpose of the motor thermal protection application 32 is to protect the electric motor from overheating. The motor thermal protection application 32 is based on the IEC 60947 standard.
[0056] This standard defines the error threshold θ errorand a theoretical mathematical model representing the thermal evolution of the electric motor. The motor thermal protection application 32 calculates the theoretical mathematical model at each start-up of the motor based on motor-specific data and data measured during each start-up. The motor-specific data includes the motor's rms nominal current and the motor's protection class. The data measured during each start-up includes the duration of each start-up and the instantaneous current through the arm during the start-up.
[0057] Optionally, the soft starter 6 includes a display screen 34 connected to the processor.
[0058] When the thermal state calculated according to the theoretical mathematical model reaches the error threshold θ defined by the standard error The Motor Thermal Protection application will trigger a Motor Thermal Fault when
[0059] The theoretical mathematical model representing the evolution of the thermal state of an electric motor, as defined by standard IEC 60947, is given by the following equation (1): This thermal model is a first-order filter applied on the square of the current ratio.
[0060]
[0061] where θ(t) is the thermal state of the electric motor,
[0062] I n is the rms nominal current of the electric motor,
[0063] I RMS is the average value of the rms current flowing through each of the three arms of the starter during starting of the electric motor,
[0064] τ can be the thermal time constant of copper or the thermal time constant of iron. Cu Represents the temperature rise of the electric motor. The thermal time constant τ of iron Fe Represents the cooling of electric motors. The thermal time constant depends on the motor protection class. The following table gives examples of time constants according to the motor protection class.
[0065]
[0066]
[0067] For the first start of the electric motor, the thermal model defined by equation (1) can be written as:
[0068]
[0069] in And I n and I RMS As defined in equation (1),
[0070] θ1 is the thermal state of the electric motor after a start-up. θ1 is calculated at each sampling time of the processor 26 .
[0071] θ0 is the initial thermal state of the electric motor, which is equal to zero when it is first started.
[0072] t is the current time during first boot.
[0073] For the following start-up of an electric motor, the thermal model defined by equation (1) can be written as:
[0074]
[0075] in
[0076] t cur Is the current time during the current boot.
[0077] θ prec is the previous thermal state of the electric motor.
[0078] θ cur is the current thermal state of the electric motor. Current thermal state θ cur is calculated at each sampling time by the processor 26.
[0079] During the cooling period of the electric motor, the current thermal state between two starts is also calculated.
[0080] For the present disclosure, we consider all starts to be identical. In particular, we consider that the duration of all starts is equal to the duration of the first start and that the current I supplied to one winding of the electric motor during the on-state of all starts is equal to RMS The current I supplied to one winding of the electric motor during the initial start-up RMSstart Taking these factors into consideration, equation (1) can be written as follows for startup, which will cause tripping of the electric motor thermal fault by the electric motor thermal protection application 32 .
[0081]
[0082] in
[0083] θ lim is the extreme thermal condition, i.e. the thermal condition before start-up, during which the thermal protection will trigger a motor thermal fault.
[0084] θ error Is the error threshold for the thermal state where the thermal protection will trigger a motor thermal fault. Error threshold θ error Defined in standard IEC60947.
[0085] Δt startis the duration of the electric motor's initial start-up.
[0086] τ may be the thermal time constant of copper or iron and is selected according to the protection class of the electric motor connected to the starter.
[0087] The method according to the present disclosure monitors the starter to warn the user before a motor thermal fault is triggered. The thermal state prior to the thermal state that will cause the motor thermal fault to trip when the motor is next started is referred to as the limit theoretical thermal state, referred to in this patent application as θ lim .
[0088] The limit thermal state θ lim It is defined by the following equation (5). This equation (4) is obtained based on equation (3).
[0089]
[0090] in:
[0091]
[0092] I n is the rms nominal current of the electric motor,
[0093] I RMSstart It is the average value of the rms current flowing through the three arms of the starter when the electric motor is first started.
[0094] τ may be the thermal time constant of copper or iron and will be chosen according to the protection class of the electric motor.
[0095] θ error is the error threshold for thermal conditions defined in standard IEC 60947.
[0096] Δt start is the duration of the electric motor's initial start-up.
[0097] Therefore, the limiting theoretical thermal state θ lim The calculation is based on the data measured during the initial start-up, data dependent on the electric motor (such as its nominal current and protection class), and data from standard IEC 60947. When the calculated current thermal state θ cur will be greater than the limiting thermal state θ lim When the motor thermal protection application 32 triggers a motor thermal fault.
[0098] Optionally, the method of the present disclosure calculates the number of possible starts n before the motor thermal fault trips via the thermal protection application 32 .
[0099] This number n is defined by the following equation:
[0100]
[0101] in:
[0102] I n and I RMS As defined in equation (1),
[0103] I n is the rms nominal current of the electric motor,
[0104] I RMS is the average value of the rms current flowing through each of the three arms of the starter during starting of the electric motor,
[0105] τ can be the thermal time constant of copper or iron, selected according to the protection class of the electric motor.
[0106] θ error is the error threshold for thermal conditions defined in standard IEC 60947.
[0107] It is the extreme thermal state of n consecutive starts.
[0108] in
[0109]
[0110] If the user does not take the warning signal into account, a motor thermal fault will be triggered. The method according to the invention can estimate the theoretical waiting time t lim , until the electric motor reaches a thermal state that allows restarting.
[0111] The theoretical waiting time t lim It can be obtained by the following equation:
[0112]
[0113] in:
[0114] τ will be the thermal time constant of copper or iron and will be chosen according to the protection class of the electric motor connected to the starter.
[0115] θ lim is the extreme thermal condition, i.e. the thermal condition before start-up, during which the thermal protection will trigger a motor thermal fault.
[0116] θ cur is the current thermal state of the electric motor.
[0117] refer to Figure 2The method for monitoring a starter begins with an initial phase 50 during which parameters P are stored in the memory unit 30. According to a first possibility, these parameters P include at least the rms nominal current In and the protection level of the electric motor connected to the starter. Preferably, the error threshold θ error and the thermal time constant τ of copper Cu and the thermal time constant τ of iron Fe are already registered in the storage unit 30, and the method is adapted to select appropriate parameters according to the protection level of the electric motor.
[0118] According to a second possibility, during the initial phase 50, the user records the rms nominal current In of the electric motor, the error threshold θ error and the copper thermal time constant τ appropriate to the protection level of its electric motor Cu and the ferroic time constant τ Fe .
[0119] This initial phase 50 is only performed once, for example the first time a user connects his starter to the electric motor.
[0120] When the processor receives a command to initiate the first start of the electric motor, the starter initiates the first start in step 52. This command may be initiated by the user (pressing a button, sending a start request via a fieldbus or applying a signal on a digital input).
[0121] The method then comprises a step 54 of determining the duration Δt of the first start start and the current I supplied to one winding of the electric motor during the start-up period of the first start RMSstart This duration can be measured by the processor timer 28. In step 54, the instantaneous current I supplied to one winding of the electric motor during the first start-up is first measured. start . Instantaneous current I start can be measured by the current determination device 25. The processor 26 then calculates the rms current I RMSstart .
[0122] Current I RMSstart may be the average value of the rms current in each of the three arms of the starter and may correspond, for example, to:
[0123]
[0124] The method then comprises a step 56 of calculating a first thermal state θ1 of the electric motor. This first thermal state θ1 is based on equation (2a), the parameter P recorded in the memory unit 30, the duration Δt determined in step 54 and start and the current I determined in step 54 during the first start-up RMSstart Theoretical limit thermal state θlim is saved.
[0125] In step 59, receive the command of opening the second start.Then open the second start of electric motor.In this disclosure, this second start and subsequent start will be named "current start".
[0126] In step 60, the current time t of the current start is determined cur The current I supplied to one winding of the electric motor during the current start is also determined. RMScur The method described in step 54 is used to determine the current I RMScur .
[0127] In step 62, based on equation (2b), the current time t cur , the current I determined in step 60 during the current startup RMScur , previous thermal state θ prec and the parameter P stored in the storage unit 30, calculate the current thermal state θ cur .
[0128] During the second start-up, the previous thermal state θ prec is the thermal state calculated for the first startup.
[0129] In step 64, the current thermal state θ cur and the limiting theoretical thermal state θ lim Make a comparison.
[0130] If the current thermal state θ cur Below the limit theoretical thermal state θ lim , then during step 66, the processor considers the current thermal state θ cur is the previous thermal state θ prec , and the method returns to step 60. During the third start-up, the previous thermal state θ prec This is the thermal state calculated for the second start, etc.
[0131] Repeat steps 60 to 64.
[0132] During these steps 60 to 64 , the user can initiate a new start of the electric motor.
[0133] If the current thermal state θ cur Greater than the limit theoretical thermal state θ lim , then in step 68 the processor sends a warning signal representing the risk of tripping a motor thermal fault.
[0134] Advantageously, thanks to the present method, a warning signal is sent just before the start, which will cause the tripping of the motor thermal fault by the starter thermal protection application 32. Thus, the user knows that he should wait before initiating a new start.
[0135] According to a first embodiment, the method includes a start-up blocking option. When this option is activated, if the processor 26 sends a warning signal and after receiving a command to start a new start, the processor 26 blocks this command in step 70 and does not start the subsequent start. Step 70 Figure 2 It is drawn with a dotted line because it is optional.
[0136] Advantageously, with this option the user cannot initiate a new start after receiving the warning signal. The start blocking option is optional.
[0137] According to a second embodiment, the method does not include a start blocking option. In this case, if the user receives a warning signal at step 68 and still initiates a new start at step 72, the motor thermal protection application 32 triggers a thermal fault.
[0138] The method may then include calculating the theoretical waiting time t lim Step 74. Theoretical waiting time t lim is the time the user must wait until the electric motor is at a low enough temperature so that the temperature increase resulting from a new start does not cause the thermal fault to be triggered.
[0139] The waiting time t lim Based on equation (6), the theoretical limit thermal state θ lim 、Current thermal state θ cur and time constant τ.
[0140] Optionally, the theoretical waiting time t lim The iron time constant τ can be used Fe and copper time constant τ Cu Then, the two theoretical waiting times t lim Compare with each other and calculate the theoretical waiting time t lim Considered as the theoretical waiting time t lim .
[0141] The method then includes displaying the theoretical waiting time t on the screen lim Step 76.
[0142] Preferably, the countdown timer 29 is displayed on the display screen 34. The countdown timer is configured to count down from the theoretical waiting time t lim Countdown to zero.
[0143] Steps 74 to 76 are optional.
[0144] Optionally, at the current thermal state θ cur Below the limit theoretical thermal state θ lim When , the method may include step 80, namely calculating the possible number of starts n before the electric motor thermal fault trips by the electric motor thermal protection application 32. Based on equations (5) and (6), the duration of the first start Δt start , the rms current I determined in step 54 during the initial startup RMSstart , electric motor parameter P and the limit thermal state (θ limn ) to calculate the possible number of starts n.
[0145] The method may then comprise a step 82 of displaying the number n of possible starts on the display screen 34 .
[0146] Finally, in step 84, the theoretical waiting time t lim It can be recorded in the memory unit 30 of the starter. If the starter has been turned off, the method includes calculating the remaining waiting time when the starter is turned on. The remaining waiting time takes into account the power off time.
[0147] The method according to the present disclosure may also be implemented as an online direct starter as a supplementary protection with respect to the thermal relay.
[0148] Figure 3 An example of the thermal evolution percentage of a motor during a 20-second acceleration at 4 times the nominal motor current is shown, with 120 seconds of no motor current between the two starts. Error threshold θ for a class 30 motor error In this case, five starts have been performed without triggering a motor thermal fault, but the sixth start triggers a motor thermal fault.
[0149] The present invention is applicable to multi-phase circuits other than three-phase circuits.
[0150] Alternatively, the limiting theoretical thermal state theta_lim may be calculated based on data from a previous startup (rather than the first startup).
[0151] In this case, there are no changes on first start-up and the data (DeltaT_start, Irms, ...) are collected as before.
[0152] So between the first and second launch, theta_lim is calculated and compared to the previous Theta_curr, but after the second launch, theta_lim is calculated based on the data from the second launch, not the first.
[0153] Before the nth start, the limit threshold is calculated based on the data of the previous start rather than the first start.
Claims
1. A method of monitoring a starter (6), the starter (6) being connected to an electrical grid (2) and an electric motor (4); the electric motor having at least one winding (20, 22, 24); the starter comprising a processor (26) and an electric motor thermal protection application (32), the electric motor thermal protection application being configured to cause tripping of an electric motor thermal fault when the electric motor (4) reaches a defined thermal condition; the method comprising: a) opening (52) the first start of the electric motor, b) Determine (54) the duration of the first start (Δt start ) and the current supplied to one winding of the electric motor during the start-up period of the first start (I RMSstart ), c) Based on the duration of the first start (Δt start ), the current supplied to one winding of the electric motor during the first start (I RMSstart ) and the parameters (P) of the electric motor to calculate (56) the ultimate theoretical thermal state (θ lim ), d) determining (60) the current (I RMScu ), e) Based on the determined current (I RMScur ) and the electric motor parameters (P) to calculate (62) the current thermal state (θ cur ), f) Comparing (64) the current thermal state (θ cur ) and the limiting theoretical thermal state (θ lim ), if the current thermal state (θ cur ) is greater than the theoretical limit thermal state (θ lim ), a warning signal representing the risk of tripping the motor thermal fault is sent (68).
2. The method according to claim 1, wherein the electric motor parameters (P) include the nominal current (In) of the electric motor, a time constant (τ) and an error threshold value (θ) of the thermal state of the electric motor. error ).
3. The method according to any one of the preceding claims, wherein if the current thermal state (θ cur ) is lower than the theoretical thermal limit (θ lim ), then repeat steps d) to f).
4. Method according to any of the preceding claims, wherein the transmission of the warning signal blocks (70) a command received by the starter to initiate the current start.
5. The method according to any one of claims 1 to 3, comprising: lim ), the current thermal state (θ cur ) and time constant (τ) to calculate (74) the theoretical waiting time (t lim ).
6. The method according to claim 5, comprising displaying (76) the theoretical waiting time (t lim ).
7. The method according to claim 5, comprising displaying (76) a countdown timer (29) on a display screen (34), the countdown timer being configured to count down from the theoretical waiting time (t lim ) counts down to zero.
8. The method according to any one of claims 2 to 5, wherein when the current thermal state (θ cur ) is lower than the theoretical thermal limit (θ lim ), the method includes calculating (80) by the electric motor thermal protection application program the number of possible starts (n) before the electric motor thermal fault trips, based on the duration (Δt start ), the current supplied to one winding of the electric motor during the first start (I RMSstart ), the electric motor parameters (P) and the limit thermal state (θ calculated for n starts limn ) to calculate the number of possible starts (n).
9. The method according to claim 8, comprising displaying (82) the number of possible starts (n) on the display screen (34).
10. The method according to claim 8 or 9, wherein if the starter is already closed, the theoretical waiting time (t lim ) is recorded (84) in a storage unit (30), the method comprising calculating a remaining waiting time when the starter is turned on, the remaining waiting time taking into account a power-off time.
11. The method according to any of the preceding claims, wherein the defined thermal condition leading to an electric motor thermal fault trip is based on a thermal protection class of the electric motor, a nominal current (In) of the electric motor and settings based on standard IEC60947.
12. A method of monitoring a starter (6), the starter (6) being connected to an electrical grid (2) and an electric motor (4); the electric motor having at least one winding (20, 22, 24); the starter comprising a processor (26) and an electric motor thermal protection application (32), the electric motor thermal protection application being configured to cause tripping of an electric motor thermal fault when the electric motor (4) reaches a defined thermal condition; the method comprising: a) opening (59) the start of the electric motor, b) determining (60) the current (I) supplied to a winding of the electric motor RMScu ), c) Based on the electric motor current (I RMSstart ) and the electric motor parameter (P) calculate (62) the current thermal state (θ cur ), d) Comparing (64) the current thermal state (θ cur ) and the first thermal state (θ lim ), if the current thermal state (θ cur ) is greater than the first thermal state (θ lim ), then it is considered that the current thermal state (θ cur ) is the previous thermal state (θ prec ), e) determining (60) the current (I) supplied to a winding of the electric motor RMScu ), f) Based on the electric motor current (I RMSstart ) and the electric motor parameter (P) calculate (62) the current thermal state (θ cur ), g) Compare (64) the current thermal state (θ cur ) and the previous thermal state (θ lim ), if the current thermal state (θ cur ) is greater than the previous thermal state (θ lim ), then a warning signal indicating the risk of motor thermal failure is sent (68).
13. A computer-readable storage medium (30) comprising instructions which, when executed by a processor (26), cause the processor to perform the method according to any one of the preceding claims.
14. A starter (6) comprising a processor including a memory unit (30) storing parameters (P) of an electric motor, the processor being suitable for implementing the method according to any one of the preceding claims.
15. The starter (6) according to claim 14, wherein the starter is a soft starter or a direct on-line starter.