CN115913044B - Start protection method and device for mining high-voltage motor - Google Patents

Start protection method and device for mining high-voltage motor Download PDF

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CN115913044B
CN115913044B CN202211533565.7A CN202211533565A CN115913044B CN 115913044 B CN115913044 B CN 115913044B CN 202211533565 A CN202211533565 A CN 202211533565A CN 115913044 B CN115913044 B CN 115913044B
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motor
current
power factor
value
fault
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CN115913044A (en
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匡欣欣
张朝平
庞现泽
卜海滨
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Shanghai Sany Electronic Technology Co ltd
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Shanghai Sany Electronic Technology Co ltd
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Abstract

The embodiment of the specification discloses a starting protection method and a protection device for a mining high-voltage motor, wherein the method comprises the following steps: obtaining the maximum phase current and the corresponding phase voltage of the motor at the current moment, and calculating a power factor based on the maximum phase current and the corresponding phase voltage if the modulus value of the maximum phase current is larger than a preset current threshold value; if the power factor meets the preset condition, judging that the motor is in short circuit fault, and sending out a fault removal instruction; and if the power factor does not meet the preset condition, eliminating the short-circuit fault of the motor. According to the technical scheme, the starting heavy current and the short-circuit fault current of the motor can be distinguished, when a short-circuit fault occurs, the fault is cut off without time delay, the duration of the fault is shortened, and the probability of burning the motor is reduced.

Description

Start protection method and device for mining high-voltage motor
Technical Field
The specification relates to the technical field of motors, in particular to a mining high-voltage motor starting protection method and a mining high-voltage motor starting protection device.
Background
The mining high-voltage motor is frequently operated under various conditions such as frequent starting, braking, positive and negative rotation, variable load and the like, and high requirements are put on a protection device of the motor.
In the prior art, the motor is started and protected by comparing the amplitude value of the current with the current fixed value and setting the delay value to avoid the motor starting super-large current or combining the two methods. The existing method has slow response speed of the protection action, and can only play a role in protecting the starting of the motor in a certain range; the existing locked rotor protection has limited protection range and can not provide protection for the condition of interphase short circuit of the motor.
In view of this, there is a need for a more efficient motor start protection scheme that improves the sensitivity and reliability of the protection.
Disclosure of Invention
The embodiment of the specification provides a protection method for solving the following technical problems: the existing motor starting protection scheme does not distinguish short-circuit current, and has the problems of low protection sensitivity, small protection range and low reliability.
In order to solve the above technical problems, the embodiments of the present specification are implemented as follows:
the embodiment of the disclosure provides a starting protection method of a mining high-voltage motor, which comprises the following steps:
obtaining the maximum phase current and the corresponding phase voltage of the motor at the current moment;
if the modulus value of the maximum phase current is larger than a preset current threshold value, calculating a power factor based on the maximum phase current and the corresponding phase voltage;
if the power factor meets the preset condition, judging that the motor is in short circuit fault, and sending out a fault removal instruction;
if the power factor does not meet the preset condition, eliminating the short-circuit fault of the motor;
wherein the current threshold and the preset condition are set according to a normal start characteristic of the motor.
According to the method of the embodiment of the disclosure, after the power factor does not meet the preset condition, the method further includes:
starting delay timing to obtain a delay time value;
when the delay timing value is smaller than a delay preset value, if the modulus value of the maximum phase current is smaller than the current threshold value, judging that the motor starts normally, and allowing the motor to start continuously;
and when the delay timing value is larger than the delay preset value, if the modulus value of the maximum phase current is larger than the current threshold value, judging that the motor is in a locked rotor fault, and sending out a fault removal instruction.
According to the method of the embodiment of the disclosure, the power factor is the rotation active power P 1 The preset condition is P1 < 0, if the rotation active power P 1 If the motor is smaller than 0, judging that the motor is short-circuit fault, and sending out fault removal instructions; if the rotation active power P 1 And not less than 0, eliminating the short-circuit fault of the motor.
According to the method of the embodiment of the disclosure, the rotation active power P is calculated 1 The expression of (2) is:wherein the method comprises the steps of
For the rotation current, the maximum Xiang Dianliu is rotated clockwise by an angle alpha, which is the remaining angle of the power factor angle set value beta, (i) 1r ，i 1i ) Is->Is used for the vector coordinates of (a),
for the corresponding phase voltage of the maximum phase current, (u) r ，u i ) Is->Is defined in the vector coordinates of (a).
According to the method of the embodiment of the disclosure, the power factor is a power factor angle θ, the predetermined condition is θ > β, wherein θ is a phase difference between the maximum phase current and the corresponding phase voltage, β is a power factor angle set value, if θ is greater than β, it is determined that the motor is a short-circuit fault, and a fault removal instruction is issued; and if the power factor angle theta is not larger than the power factor angle set value beta, eliminating the short-circuit fault of the motor.
According to the method of the embodiment of the disclosure, the power factor angle set value beta is in the range of 0 to 36 degrees.
According to the method of the embodiment of the disclosure, the obtaining the maximum phase current and the corresponding phase voltage at the current moment of the motor includes:
detecting the phase current and the phase voltage of each phase of the motor in real time to obtain a detection result;
and extracting the maximum phase current and the corresponding phase voltage at the current moment from the detection result, wherein the maximum phase current is the phase current with the maximum module value in the phase current of each phase.
Embodiments of the present disclosure also provide a mining motor protection device, the protection device including:
the operation module is used for acquiring the maximum phase current and the corresponding phase voltage of the motor at the current moment, and calculating a power factor based on the maximum phase current and the corresponding phase voltage if the modulus value of the maximum phase current is larger than a preset current threshold value;
the main control module is used for judging that the motor is in a short circuit fault when the power factor accords with a preset condition and sending out a fault removal instruction; when the power factor does not meet the preset condition, eliminating the short-circuit fault of the motor;
wherein the current threshold and the preset condition are set according to a normal start characteristic of the motor.
According to the protection device of the embodiment of the disclosure, the protection device further comprises:
the timing module is used for starting delay timing when the power factor does not accord with the preset condition;
the main control module is further configured to obtain a delay timing value of the timing module, and determine that the motor is started normally when the delay timing value is smaller than a delay set value and if the modulus value of the maximum phase current is smaller than the current threshold, allow the motor to start continuously; and when the delay timing value is larger than the delay set value, judging that the motor is in locked-rotor fault if the modulus value of the maximum phase current is larger than the current threshold value, and sending out a fault removal instruction.
According to the protection device of the embodiment of the disclosure, the power factor is the rotation active power P 1 The predetermined condition is P 1 < 0; the operation module is used for according toCalculating the rotational active power P 1 Wherein, the method comprises the steps of, wherein,
for the rotation current, the maximum Xiang Dianliu is rotated clockwise by an angle alpha, which is the remaining angle of the power factor angle set value beta, (i) 1r ，i 1i ) Is->Is used for the vector coordinates of (a),
for the corresponding phase voltage of the maximum phase current, (u) r ，u i ) Is->Is used for the vector coordinates of (a),
the value range of the power factor angle set value beta is 0-36 degrees.
The above-mentioned at least one technical scheme that this description embodiment adopted can reach following beneficial effect: and when the starting short-circuit fault is judged, the fault is cut off without delay, the fault duration is reduced, and the probability of burning the motor is reduced. In addition, the rotation active power with low operand is used as a criterion, so that the calculation efficiency is improved, and the protection sensitivity and reliability are further improved.
Drawings
In order to more clearly illustrate the embodiments of the present description or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some of the embodiments described in the present description, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a motor starting normal current curve;
FIG. 2 is a schematic diagram of a motor start-up fault current curve;
FIG. 3 is a schematic diagram of a vector rotation analysis of phase currents during motor start-up;
fig. 4 is a schematic flow chart of a motor start protection method according to a first embodiment of the present disclosure;
fig. 5 is a schematic flow chart of a motor start protection method according to a second embodiment of the present disclosure;
fig. 6 is a schematic diagram of motor start stall protection logic according to a second embodiment of the present disclosure;
fig. 7 is a block diagram of a motor start protection device according to a third embodiment of the present disclosure;
fig. 8 is a block diagram of a motor start protection device according to a fourth embodiment of the present disclosure;
fig. 9 is a block diagram of a motor start protection device according to a fifth embodiment of the present disclosure.
Detailed Description
In order to make the technical solutions in the present specification better understood by those skilled in the art, the technical solutions in the embodiments of the present specification will be clearly and completely described below with reference to the drawings in the embodiments of the present specification, and it is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.
Several protection schemes exist, which are first analyzed based on the current characteristics at motor start-up.
The starting phase of the motor, in which the current in the motor supply circuit, called the starting current, refers to the process of starting from the closing of the mains switch, the motor speed going from zero to a steady speed. The starting current exhibits a change from large to small and eventually to steady state, which is the requisite phase of normal motor start.
As shown in fig. 1, under normal conditions, the current before the motor starts is zero, and after the circuit breaker is closed, the current increases instantaneously, and as the rotation speed of the motor increases, the current of the motor gradually decreases. When the motor reaches the rated rotation speed, the current of the motor is stabilized near the rated current. In fig. 1, when the current I of the motor is less than 0.1 times the rated current, the motor is considered to be in a stopped state. From time t1, the motor current is zero, and the motor is considered to be in a start state. After the start, the current is reduced from the large value and stabilized around the rated current Ie, and the motor is considered to have entered the steady operation state from the time t 2. As shown in fig. 2, in the failure state, when the motor is started, the time T elapses set After that, the current still cannot be reduced to the vicinity of the rated current and still is 1.1 times larger than the rated current, and the motor is considered to be started to be failed, T set The setting value of the motor is a value slightly longer than the longest starting time of the motor, and is related to the characteristics of the motor itself.
The start timeout protection is to judge the current of the motor after the set start time, and if the current is larger than 1.1 times of rated current, the motor is considered to be in fault, otherwise, the motor is considered to be normal. Because of fixed delay, if the motor is short-circuited during starting, the motor cannot be immediately stopped for starting, and the motor is easy to burn.
The inverse time limit overload protection is generally set according to three inverse time limit characteristic curves of international standard, the action time of the protection device is inversely proportional to the magnitude of short-circuit current, the larger the current flowing through the relay is, the shorter the action time is, and the longer the action time is, the larger the current when the motor is started is avoided according to the principle. The scheme still carries out judgment based on the current amplitude and action delay, so that the motor starting fault cannot be accurately judged.
In addition, in the starting process of the motor, the motor shaft is blocked due to overlarge load or self mechanical reasons, and after the motor is blocked, a stator winding flows a large current which is 5-12 times of rated current, so that the motor is easy to burn out, and the blocking protection is designed. The locked rotor protection scheme has the advantages that due to the small delay, when the motor is locked, the current flowing through the stator winding is always in a fault state before the end of the small delay timing, so that the stator winding of the motor heats, and the insulation performance and the structural performance of the motor are seriously affected.
Next, the relationship between the characteristics of the motor starting current and the power factor is analyzed.
The motor converts electric energy into kinetic energy through electromagnetic induction principle, and belongs to inductive load. The inductance of the motor winding resists the change of current, when the current flowing through the motor winding changes, induced electromotive force is generated at two ends of the motor winding, and the polarity of the induced electromotive force resists the change of current; when the current increases, the current will be hindered from increasing, and when the current decreases, the current will be hindered from decreasing in turn. This prevents abrupt changes in the current through the inductor, which is characteristic of an inductive load, so that the inductive load current lags the load voltage by a phase difference of at most 90 °, which phase difference is also referred to as the power factor angle. In polar coordinates shown in FIG. 3, with voltage vectorsFor reference, current vector +.>Falling within the fourth quadrant due to the lagging phase difference, assuming that the current at the time of normal start of the motor is +.>At this time, the corresponding power factor angle is θ, and the power factor of the motor is cos θ.
When the motor starts to rotate, excitation is required to be obtained to enable the motor to rotate, and as the rotating speed and the load increase, the current changes with time, and the power factor also gradually increases. In general, the power factor of the motor is gradually increased from about 0.2 to about 0.7 in steady state when the motor is started, and the corresponding power factor angle is changed between 80 degrees and 45 degrees.
Single-phase and phase-to-phase short-circuit faults may occur when the motor is started. A short circuit refers to the situation when two points of different potential in the circuit are incorrectly touched directly or turned on by a very small impedance conductor. The current in the circuit is very large during short-circuit, and the impedance approaches zero, and the power factor at this time is usually above 0.8. The single-phase short circuit fault and the interphase short circuit fault are collectively referred to as a short circuit fault in this disclosure.
The inventors found that the difference in the power factor of the motor between the short-circuit fault and the normal start can distinguish the fault current. Based on this finding, the inventors propose the solution of the present application, achieved by a protection device provided in the motor.
As shown in fig. 4, a motor start protection method provided in the first embodiment of the present disclosure includes steps S110 to S132.
S110: and acquiring the maximum phase current and the corresponding phase voltage of the motor at the current moment.
S120: and if the modulus value of the maximum phase current is larger than a preset current threshold value, calculating a power factor based on the maximum phase current and the corresponding phase voltage.
S131: if the power factor meets the preset condition, judging that the motor is in short circuit fault, and sending out a fault removal instruction.
S132: and if the power factor does not meet the preset condition, eliminating the short-circuit fault of the motor.
The current threshold and the preset condition in the above steps are set according to the normal start-up characteristic of the motor.
According to the scheme of the embodiment, the power factor is used for distinguishing the starting heavy current and the short-circuit fault current of the motor, when the short-circuit fault is started, the fault is cut off without time delay, the fault duration is shortened, and the probability of burning the motor is reduced.
The principle of the first embodiment will be described below.
Protection device arranged in motor, when motor is started, sampling and calculating phase current of each phase of three-phase motor, namely FFT (fast Fourier transform) calculation is carried out on sampling result of analog quantity of phase current, phase current and phase voltage can be converted into vector form, namely vector phase currentPhase voltage of sum vector->(hereinafter, abbreviated as phase current and phase voltage), the phase active power at the time of motor start is:
equation (1) is a scalar calculation method of active power.
Voltage of vectorCan be expressed by vector coordinate method (ur, ui), the current of vector +.>Can be obtained by vector coordinate method (i r ，i i ) The phase active power at motor start can also be calculated as follows:
calculating the active power P by using the formula (2) and calculatingModulus and>the power factor cos theta at the start of the motor can be calculated by using the formula (2), and then the power factor angle theta can be obtained.
In some cases, the power factor in S120 of the first embodiment may be the power factor angle θ obtained by the above method, that is, the phase difference between the actual current and the actual voltage. Of course, based on the correspondence of the angle and the cosine value, the same principle as the power factor angle θ is used as the power factor, and the present disclosure is described by taking the power factor angle θ as an example only, and does not exclude the implementation of the power factor cos θ as the power factor.
When calculating using formula (1), vector voltages are calculatedIs equal to the modulus and vector current->The modulus of (2) requires a root-number calculation, e.g., voltage +.>Is +.>Division is also performed when calculating the power factor cos θ. When the single chip microcomputer is used for realizing, the time consumed by root opening and division operation is longer, and the time is far longer than the time consumed by multiplication operation, so that the performance requirement on the single chip microcomputer is higher. In order to improve the operation efficiency and reduce the operation time consumption, an embodiment of the disclosure also provides another low operation amount method, which is specifically as follows.
Therefore, in other cases, the power factor in step S120 may be the rotation active power P for the purpose of reducing the computation amount 1 And calculated by means of vector coordinates, i.eThe principle of this calculation is specifically described below with reference to fig. 3.
As shown in fig. 3, the vector voltage for maintaining motor startInvariably, vector current of motor +.>Rotating alpha angle clockwise to obtain new vector current +.>Its vector coordinate representation (i) 1r ，i 1i ). Post-rotation vector current>The modulus of (2) is unchanged, i.e.)>But the phase is changed. From the rotation formula of the vector, can be derived +.>And->The coordinate relationship of (2) is:
i 1r ＝i r *cosα+i i *sinα
i 1 i＝i i *cosα-i r *sinα (3)
the rotation angle α is the complement of the actual power factor angle θ, i.e., α=90° - θ. Because the value range of the angle theta is (0-90 degrees), and the value range of the angle alpha is (0-90 degrees), the expression of the power factor angle of the motor starting can be converted into the expression of the formula (3):
i 1r ＝ir*sinθ+i i *cosθ
i 1i ＝i i *sinθ-i r *cosθ (4)
setting the active power obtained after the current vector rotates as P 1 Then
P 1 ＝u r *i lr +u i *i li (5)
It can be seen that P can be calculated using equation (4) and equation (5) 1 . When the power factor angle theta is a set value,calculating a set rotational active power P 1 The operation amount of the power factor angle calculation method is greatly reduced, only a few times of multiplication and addition operation are performed, and compared with a method for calculating the real-time power factor angle, the power is saved, and the efficiency is improved.
Therefore, the power factor calculated in step S120 may be either the power factor angle θ or the set rotational active power P 1 . At this time, the starting current is determined in combination with the power factor, and if a short-circuit fault is determined, the fault can be directly cut off without waiting for a delay time, so that the duration of the fault is reduced.
In steps S131 and S132, when the power factor is the power factor angle or the rotational active power, the corresponding preset conditions are also different, but are set according to the normal start characteristics of the motor.
The analysis is now based on the difference in power factor in both the case of a normal motor start and the case of a short circuit at motor start:
a) If the motor is started normally, the power factor cos theta gradually rises from about 0.2 to about 0.7 of a steady state, the power factor angle theta at the time of starting the motor is between (80-45 degrees), and the power factor angle is larger and tends to 80 degrees in the process that the motor starts to start and reaches the maximum starting current;
b) If the motor has a short circuit fault during starting, the power factor cos theta is more than 0.8, and the power factor angle theta during starting the motor is between (0 and 36 degrees);
c) From the above analysis, a set value of the power factor angle may be given to distinguish whether the motor start is a normal start or a short-circuit fault, for example, the power factor angle set value β=36°, the actual power factor angle at the time of the motor start is θ, and θ < β when the motor start indicates that the motor start is in a short-circuit fault state; similarly, when the motor is started, theta is larger than beta, which indicates that the motor is started normally;
d) Rotating the active power P according to a scalar formula for calculating the active power 1 Is that
The rotation angle alpha=90° -beta, and the formula (6) can be converted into
As can be seen from equation (7), when θ < β, sin (θ - β) < 0, P 1 < 0; when theta > beta, sin (theta-beta) > 0, P 1 ＞0。
Thus, when the beta value is given, the vector current is rotated by 90 degrees to beta degrees, and the rotation active power P is calculated 1 The positive and negative values thereof may reflect the characteristics of the actual current. For example, given a beta value of 30 deg. and an actual power factor angle of around 40 deg., the vector current will fall into the third quadrant beyond 90 deg. after 60 deg. rotation, as shown in fig. 3At this time according to->P calculated from vector coordinates of (c) 1 A negative value can be determined as a short-circuit fault in motor start.
Based on the above principle, when calculating the rotation active power Px, it can be performed by using vector coordinates, i.e., equation (5), at this time, P is calculated 1 The operation amount of the method is small, and only a few times of multiply-add operation is performed, so that the calculation force is saved, and the efficiency is improved. And calculated P 1 The positive and negative values of (a) can reflect the characteristics of the actual current, and it can be determined whether or not the current is a short-circuit fault.
From the above analysis, it can be seen that the angular range of the power factor can be used to distinguish between a normal start or a short circuit fault of the motor, and the rotational active power P can also be used 1 To distinguish between a normal start of the motor or a short circuit fault. The positive and negative values of the rotary active power are used as power factors for judgment, so that the calculation force can be saved, the calculation efficiency is higher, and the protection sensitivity is further improvedAnd reliability, are preferred.
Therefore, in the implementation, if the power factor angle θ is taken as the power factor, the power factor angle θ is calculated in step S120, and it is determined that the corresponding preset condition of the start short-circuit fault is θ < β, β is the set value of the power factor angle, and the range is 0 ° to 36 °, and may be specifically set according to the requirement of the protection sensitivity. If in practice, to rotate the active power P 1 As a power factor, the rotational active power P is calculated in step S120 1 The preset condition for judging the start short-circuit fault at this time corresponds to P 1 < 0, and the calculation of vector coordinates can be used to save computational effort. It will be appreciated that the preset condition is related to the current characteristics of the normal start of the motor.
Before the motor starts, the motor can be set according to the characteristics of the motor, for example, the maximum value of the starting current is set as a current threshold value, and a delay set value is set, wherein the delay set value is a value slightly larger than the setting value of the motor, so that the motor starts safely.
In step S110, the maximum phase current and the corresponding phase voltage at the current time of the motor are obtained by the detection result of the detection module. For example, the detection module detects the phase current and the phase voltage of each phase in real time during the starting process of the motor, provides a detection result, wherein the detection result comprises the phase current and the phase voltage of each phase, the detection result is provided in a vector form, the operation module extracts the phase current with the maximum modulus value from the detection result as the maximum phase current at each judging moment, and then compares the maximum phase current with a current threshold value, and the maximum phase current is the phase current with the maximum modulus value in the phase current of each phase. In the implementation, efficiency and precision can be considered, on the one hand, a proper time interval can be set for judgment, for example, the maximum phase current is extracted every 5ms, comparison and judgment are carried out, when the maximum phase current is larger than a current threshold value, the power factor is calculated by using the maximum phase current and the corresponding phase voltage, and then whether the preset condition of short circuit fault is met or not is judged. On the other hand, when the phase current having the maximum modulus is extracted and when the phase current is compared with the current threshold, the square value of the current modulus can be used for comparison, and the root-open operation can be avoided.
In the first embodiment, the starting current is distinguished by the power factor (the power factor angle or the rotational active power), and when the motor is started, a single-phase short-circuit fault and an inter-phase short-circuit fault occur, so that the faults can be directly cut off, the fault duration is reduced, and the protection sensitivity and reliability are improved.
The locked rotor protection scheme provided in the second embodiment is a more perfect protection scheme on the scheme of the first embodiment.
As shown in fig. 5, the motor start protection method provided in the second embodiment of the present disclosure includes steps S210 to S260.
S210: and acquiring the maximum phase current and the corresponding phase voltage of the motor at the current moment.
S220: if the modulus of the maximum phase current is greater than a preset current threshold, calculating a power factor based on the maximum phase current and the corresponding phase voltage.
S231: if the power factor meets the preset condition, judging that the motor is in short circuit fault, and sending out a fault removal instruction.
S232: and if the power factor does not meet the preset condition, eliminating the short-circuit fault of the motor.
S240: and starting a preset delay timer to acquire a delay timer value.
S250: when the delay timing value is smaller than the delay set value, if the modulus value of the maximum phase current is smaller than the current threshold value, the motor is judged to be started normally, and the motor is allowed to be started continuously.
S260: when the delay timing value is larger than the delay set value, if the modulus value of the maximum phase current is larger than the current threshold value, the motor is judged to be in locked-rotor fault, and a fault removal instruction is sent out.
The details of steps S210 to S232 are described in the first embodiment, and can be implemented with reference to the first embodiment.
Step S240, after branching step S232, i.e. when it is determined that the starting current is not the short-circuit current, after the short-circuit fault is removed, starts a small delay time to further distinguish whether it is the locked-rotor current. The delay setting value may be set at the time of motor configuration, and is slightly greater than the time when the starting current of the motor rises to the maximum value, that is, the delay setting value is greater than the setting value of the motor, so that the delay can reserve the current change time for normal starting to the motor, but the delay is not too long to cause damage to the motor, for example, the time when the starting current of a certain motor rises to the maximum value is 50ms, and the delay setting value of the small delay may be set to 55ms.
In steps S250 and S260, during the preset delay period, that is, during the period when the timer value does not reach the delay set value, if the detected maximum phase current has a modulus value smaller than the current threshold value and meets the variation curve of the normal starting current, the motor is determined to be started normally, and the motor is allowed to continue to start. And when the delay expires, namely the timing value is larger than the delay set value, if the modulus value of the maximum phase current is still larger than the current threshold value, determining that the phase current is a locked rotor fault, and sending out a fault removal instruction.
According to the scheme of the second embodiment, before the motor determines the locked rotor fault, the judgment on the short circuit fault is increased, and the damage time of the short circuit current to the motor during starting is reduced, so that the sensitivity and the reliability of the locked rotor protection logic are improved.
The scheme of the second embodiment is applied to implement the principle of locked rotor protection.
The motor stall is a condition that the motor still outputs torque when the rotating speed is 0 rotation, and is generally a phenomenon that the motor cannot start or stop rotating due to mechanical or artificial reasons, for example, the motor is excessively loaded, mechanical faults caused by dragging, damage to a bearing, bore sweeping and the like.
When the motor rotates, the rotating magnetic field formed by the stator winding drags the rotor to rotate, and the magnetic field generated by the induced current in the rotor also induces counter potential, namely inductive reactance, in the stator winding, so as to play a role in preventing the current of the motor stator from increasing. If the motor is locked, the counter potential is not generated, and the motor is like an inductance element connected in a power supply, and only the resistance and inductance of the motor are adopted, so that the natural current can be greatly increased. The motor operates with back emf, which is a major proportion of the consumption voltage. The counter potential is zero during locked-rotor, and all voltages are loaded on the windings, so that the current is large. According to the different sizes of motor capacity and processing technique, the motor locked-rotor current is generally 5-12 times of the rated current of the motor. Therefore, the power factor is also extremely low when the motor is locked.
Since the locked-rotor current of the motor is not clearly distinguished from the maximum current when the motor is started and the power factor is low, the locked-rotor current and the maximum starting current cannot be distinguished directly by the power factor (i.e., the aforementioned power factor angle or the rotational active power). However, depending on the starting current characteristics of the motor, a small delay T may be provided by rapidly increasing the current to a maximum value after the motor is started and then decreasing to the rated current level set For distinguishing between a locked-rotor current and a normal start maximum current, the delay time is slightly longer than the time when the start current rises to the maximum value.
Based on the above principle, in the scheme of the second embodiment of the present disclosure, in the existing locked rotor protection scheme, a logic for judging the short-circuit current is added, so that the problems of incomplete judgment and low reliability of the locked rotor fault in the prior art are solved.
FIG. 6 to employ rotational active power P 1 As an example of the power factor, a motor protection logic diagram of the application embodiment two is given, with which a short-circuit fault, a locked-rotor fault, and a normal start large current can be effectively distinguished.
As shown in FIG. 6, when the motor is started, the phase current of each phase is detected, and the maximum phase current is extracted to determine whether the current threshold is exceeded, i.e., whether I > I set If so, calculating the rotation active power P 1 ；
Judging P 1 When P 1 Less than 0, judging that the motor is started in a short-circuit fault state, and directly sending out a fault removal instruction by the protection device without timing with small delay;
when not meeting P 1 If the value is less than 0, eliminating the short circuit of the motor, starting the counting with small delay to obtain a timing value T cnt ；
During the time of counting, i.e. T cnt ＜T set If the actual current I is less than I swt Indicating that the starting current of the motor starts to decrease from the maximum value, judging that the motor starts normally, and enabling the motor protection device to continue to allow the motor to start normally;
after expiration of the timer, T cnt ＞T set If the actual current I > I set And the motor protection device sends out a fault removal instruction when the motor is locked during starting.
T cnt For the timing value of the delay period, T set Is a delay setting value of small delay.
Because the short-circuit current is far greater than the locked-rotor current, the motor is easy to burn out, and the fault is cut off as soon as possible due to the need of distinguishing. According to the scheme of the second embodiment of the present disclosure, in the motor starting protection logic, the judgment of the short circuit current is added, so that the defect that the existing locked rotor protection logic cannot identify the short circuit current is overcome. When the current property is judged to be short-circuit current, the fault is directly cut off without small delay, and the probability of burning out the motor is reduced.
Based on the same inventive concept, a third embodiment of the present disclosure provides a starting protection device 300 for a mining high-voltage motor.
Fig. 7 schematically illustrates a block diagram of a protection device 300 according to an embodiment of the disclosure. The protection device 300 may be implemented as part or all of an electronic device by software, hardware, or a combination of both.
As shown in fig. 7, the protection device 300 includes an operation module 310 and a main control module 320.
The operation module 310 is configured to obtain a maximum phase current and a corresponding phase voltage at a current time of the motor, and calculate a power factor based on the maximum phase current and the corresponding phase voltage if a modulus value of the maximum phase current is greater than a preset current threshold.
The main control module 320 is configured to determine that the motor is in a short-circuit fault when the power factor meets a preset condition, and send a fault removal instruction, and remove the short-circuit fault of the motor when the power factor does not meet the preset condition.
According to the protection device of the third embodiment of the disclosure, the starting current is distinguished through the power factor, and when the motor is started, a single-phase short circuit fault and an interphase short circuit fault occur, so that the faults can be directly cut off, the duration of the faults is reduced, and the protection sensitivity and reliability are improved.
Based on the same inventive concept, the fourth embodiment of the present disclosure also provides a starting protection device 400 for a mining high-voltage motor.
Fig. 8 schematically illustrates a block diagram of a protection device 400 according to an embodiment of the disclosure. The protection apparatus 400 may be implemented as part or all of an electronic device by software, hardware, or a combination of both.
As shown in fig. 8, the protection device 400 includes an operation module 410, a main control module 420, and a timing module 430.
The operation module 410 is configured to obtain a maximum phase current and a corresponding phase voltage at a current time of the motor, and calculate a power factor based on the maximum phase current and the corresponding phase voltage if a modulus value of the maximum phase current is greater than a preset current threshold.
The main control module 420 is configured to determine that the motor is in a short circuit fault and send out a fault removal instruction when the power factor meets a preset condition, obtain a delay timing value of the timing module 430 when the power factor does not meet the preset condition, and determine that the motor is normally started if the delay timing value is smaller than a delay set value and allow the motor to continue to start if the modulus value of the maximum phase current is smaller than a current threshold; when the delay timing value is larger than the delay set value, if the modulus value of the maximum phase current is larger than the current threshold value, judging that the motor is in locked-rotor fault, and sending out a fault removal instruction.
The timing module 430 is configured to start delay timing when the power factor does not meet a preset condition.
According to the protection device of the fourth embodiment of the present disclosure, in the motor starting protection logic, the judgment of the short circuit current is added, so that the defect that the existing locked rotor protection logic cannot identify the short circuit current is overcome. When the current is judged to be short-circuit current, the fault is directly cut off without small delay, and the probability of burning out the motor is reduced.
In the protection device of the third and fourth embodiments above, the active power P can be rotated 1 As a power factorA sub-set, wherein the preset condition adopted by the main control module in judgment is P 1 < 0, wherein the operation module is based onCalculating to obtain rotary active power P 1 Wherein->For the rotation current, the maximum Xiang Dianliu is rotated clockwise by an angle alpha, which is the remaining angle of the power factor angle set value beta, (i) 1r ，i 1i ) Is->Vector coordinates of>The corresponding phase voltage (ur, ui) being the maximum phase current is +.>The value range of the power factor angle set value beta is 0-36 degrees.
By adopting the operation mode, the calculation force of the operation module can be saved, the calculation efficiency is higher, and the protection sensitivity and reliability are further improved.
In the protection device of the third embodiment and the fourth embodiment, the protection device may further include a detection module, configured to detect a phase current and a phase voltage of the motor in a starting stage, and provide a real-time detection result, so that the operation module may extract a maximum phase current and a corresponding phase voltage at a current time from the detection result, and perform subsequent comparison and operation.
Thus, on the basis of the fourth embodiment, the present disclosure also provides a start-up protection device 500 for a mining high-voltage motor of the fifth embodiment, as shown in fig. 9.
Fig. 9 schematically illustrates a block diagram of a protection device 500 according to a fifth embodiment of the present disclosure. The protection device 500 may be implemented as part or all of an electronic device by software, hardware, or a combination of both.
As shown in fig. 9, the protection device 500 includes a detection module 510, an operation module 520, a main control module 530, and a timing module 540.
The detecting module 510 is configured to detect a phase current and a phase voltage of a motor in real time, and obtain a detection result, so that the computing module 520 can extract a maximum phase current and a corresponding phase voltage at a current moment from the detection result, where the maximum phase current is a phase current with a maximum module value in the phase current of each phase.
The implementation of the operation module 520, the main control module 530, and the timing module 540 may be implemented with reference to the modules corresponding to the fourth embodiment.
The foregoing describes specific embodiments of the present disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for the apparatus embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for relevant points.
The foregoing description is by way of example only and is not intended as limiting the application. Various modifications and variations of the present application will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.

Claims (6)

1. A method for protecting the starting of a mining high-voltage motor, the method comprising:
obtaining the maximum phase current and the corresponding phase voltage of the motor at the current moment;
setting a time interval for judgment, and calculating a power factor based on the maximum phase current and the corresponding phase voltage if the modulus value of the maximum phase current is larger than a preset current threshold value at each judgment moment;
if the power factor meets the preset condition, judging that the motor is in short circuit fault, and sending out a fault removal instruction;
if the power factor does not meet the preset condition, eliminating the short-circuit fault of the motor, starting delay timing, and obtaining a delay time value; when the delay timing value is smaller than a delay preset value, if the modulus value of the maximum phase current is smaller than the current threshold value, judging that the motor starts normally, and allowing the motor to start continuously; when the delay timing value is larger than the delay preset value, if the modulus value of the maximum phase current is larger than the current threshold value, judging that the motor is in a locked rotor fault, and sending out a fault removal instruction;
the current threshold and the preset condition are set according to the normal starting characteristic of the motor, the power factor is a power factor angle theta, the preset condition is theta > beta, wherein the power factor angle theta is the phase difference between the maximum phase current and the corresponding phase voltage, and beta is a power factor angle set value.
2. The method of claim 1, wherein if the power factor angle θ is greater than the power factor angle setpoint β, determining that the motor is a short circuit fault, issuing a fault removal command; and if the power factor angle theta is not larger than the power factor angle set value beta, eliminating the short-circuit fault of the motor.
3. A method according to claim 1 or 2, characterized in that the power factor angle set point β has a value in the range of 0 ° to 36 °.
4. The method of claim 1, wherein the obtaining the maximum phase current and the corresponding phase voltage for the current time of the motor comprises:
detecting the phase current and the phase voltage of each phase of the motor in real time to obtain a detection result;
and extracting the maximum phase current and the corresponding phase voltage at the current moment from the detection result, wherein the maximum phase current is the phase current with the maximum module value in the phase current of each phase.
5. A mining motor protection device, characterized in that the protection device comprises:
the operation module is used for acquiring the maximum phase current and the corresponding phase voltage of the motor at the current moment, judging according to the set time interval, and calculating a power factor based on the maximum phase current and the corresponding phase voltage if the modulus value of the maximum phase current is larger than a preset current threshold value at each judging moment;
the timing module is used for starting delay timing when the power factor does not accord with a preset condition;
the main control module is used for judging that the motor is in a short circuit fault when the power factor accords with a preset condition and sending out a fault removal instruction; when the power factor does not meet the preset condition, eliminating the short-circuit fault of the motor; the main control module is further configured to obtain a delay timing value of the timing module, and determine that the motor is started normally when the delay timing value is smaller than a delay set value and if the modulus value of the maximum phase current is smaller than the current threshold, allow the motor to start continuously; when the delay timing value is larger than the delay set value, if the modulus value of the maximum phase current is larger than the current threshold value, judging that the motor is in locked-rotor fault, and sending out fault removal instructions;
the current threshold and the preset condition are set according to the normal starting characteristic of the motor, the power factor is a power factor angle theta, the preset condition is theta > beta, wherein the power factor angle theta is the phase difference between the maximum phase current and the corresponding phase voltage, and beta is a power factor angle set value.
6. The protection device according to claim 5, wherein the power factor angle set point β has a value ranging from 0 ° to 36 °.
CN202211533565.7A 2022-12-01 2022-12-01 Start protection method and device for mining high-voltage motor Active CN115913044B (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN202663087U (en) * 2012-06-15 2013-01-09 深圳普鲁士特空压系统有限公司 Smart protector for motor
CN104393575A (en) * 2014-10-24 2015-03-04 上海山源电子科技股份有限公司 Phase-sensitive protection method and system for coal mine low-voltage distribution protector
CN105186931A (en) * 2015-09-09 2015-12-23 乐晓蓉 Identification method of fault current in starting process of asynchronous motor
CN114518534A (en) * 2020-11-19 2022-05-20 杭州先途电子有限公司 Control method and controller
CN115173744A (en) * 2022-07-22 2022-10-11 帝森克罗德集团有限公司 Y/delta starting control module of motor protection controller

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN202663087U (en) * 2012-06-15 2013-01-09 深圳普鲁士特空压系统有限公司 Smart protector for motor
CN104393575A (en) * 2014-10-24 2015-03-04 上海山源电子科技股份有限公司 Phase-sensitive protection method and system for coal mine low-voltage distribution protector
CN105186931A (en) * 2015-09-09 2015-12-23 乐晓蓉 Identification method of fault current in starting process of asynchronous motor
CN114518534A (en) * 2020-11-19 2022-05-20 杭州先途电子有限公司 Control method and controller
CN115173744A (en) * 2022-07-22 2022-10-11 帝森克罗德集团有限公司 Y/delta starting control module of motor protection controller

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