CN111257749B - Offline measurement method for parameters of linear induction motor - Google Patents
Offline measurement method for parameters of linear induction motor Download PDFInfo
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- CN111257749B CN111257749B CN201811448120.2A CN201811448120A CN111257749B CN 111257749 B CN111257749 B CN 111257749B CN 201811448120 A CN201811448120 A CN 201811448120A CN 111257749 B CN111257749 B CN 111257749B
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Abstract
The invention discloses an off-line measuring method of linear induction motor parameters, which comprises the following steps: blocking the measured linear induction motor to ensure an air gap between primary stages; the primary side of the tested motor is connected with a rated frequency, sinusoidal voltages with different amplitudes are applied, the amplitudes are gradually increased until the primary current is close to the rated value, the terminal voltage of a primary winding under the voltages with different amplitudes, the primary current and the primary input power are recorded, and a short-circuit characteristic curve is drawn; the power motor drags the tested motor to a constant speed; the primary side of the motor to be measured is introduced with sinusoidal voltage which advances in the reverse direction and has the frequency corresponding to the primary motion speed, the amplitude is gradually increased to be close to a rated value, the terminal voltage, the primary current and the primary input power of a primary winding are recorded, and a no-load curve is drawn; and (3) combining the equivalent circuit of no-load and short circuit, solving the excitation resistance and the excitation inductance at the speed by using the obtained curve, changing the dragging speed of the power motor, and repeating the steps. The invention realizes the measurement of the parameters of the linear induction motor.
Description
Technical Field
The invention belongs to the field of linear induction motor parameter measurement, and particularly relates to an offline linear induction motor parameter measurement method.
Background
In the field of traction transmission, the linear induction motor has low noise because of no intermediate transmission device; the traction force is not influenced by static friction force, and the climbing capability is strong; no mechanical contact exists, so the mechanical loss is small; the motor has no centrifugal force and good structural robustness. Fig. 1 is a schematic structural view of a conventional linear induction motor, as shown in fig. 1, including a primary stage and a secondary stage. The primary and secondary are separated horizontally, and the heat dissipation effect is good. However, fig. 2 is a schematic diagram of an edge effect of a conventional linear induction motor, as shown in fig. 2, a second type of longitudinal edge effect occurs due to a linear structure of the linear induction motor, and the effect causes eddy currents to be induced at a secondary input end and a secondary output end, so that an equivalent excitation inductance changes along with the edge effect, and a problem of inaccurate modeling of the linear induction motor is always troubled.
For the structural characteristics of linear induction motors, the current mainstream method is to measure initial parameters such as resistance and inductance through the T-type equivalent static state of the common induction motor. Then, considering the side end effect, and fitting the resistance inductance change rule in the dynamic process by adopting a Duncan model. The Duncan model is mathematically derived through energy equivalence to obtain approximate variation relation between excitation resistance and inductance along with speed. And an accurate loss model is not completely established at present. Especially in the application occasions of high power and large air gap such as magnetic suspension, the accuracy degree of the model is questionable. In addition, a large number of scholars perform online identification of parameters based on the mathematical model, but only a few parameters with very obvious changes can be identified, and online identification presupposes that the model and other parameters are very accurate. For the reasons, the accurate solution of the linear motor model still has certain problems.
Disclosure of Invention
Aiming at the defects or improvement requirements in the prior art, the invention provides an offline parameter measuring method for a linear induction motor, and aims to solve the problem that the control precision is reduced because the change of the excitation resistance and the inductance of the motor along with the speed is obvious and a mathematical model is difficult to accurately establish due to the side end effect of the linear induction motor.
In order to achieve the above object, the present invention provides an off-line measuring method for parameters of a linear induction motor, comprising the following steps:
(1) the primary position of the linear induction motor to be detected is fixed by locking the rotor, so that the linear induction motor to be detected is short-circuited, and the size of an air gap between the primary and secondary is ensured to be unchanged;
(2) introducing first sinusoidal voltages with rated frequency and different amplitudes to the primary side of the short-circuited linear induction motor to be detected, gradually increasing the amplitudes until the primary current reaches the rated value, and recording the terminal voltage, the primary current and the primary input power of a primary winding under different amplitude voltages so as to determine the short-circuit characteristic curve of the linear induction motor to be detected;
(3) dragging the primary side of the linear induction motor to be detected to a preset speed, wherein the preset speed is within a traveling speed range when the linear induction motor works at the primary side;
(4) after the primary is dragged to a preset speed, introducing a second sinusoidal voltage which advances in the reverse direction and has a frequency determined by the preset speed into the primary of the linear induction motor to enable the linear induction motor to be tested to be in no-load, gradually increasing the amplitude of the second sinusoidal voltage until the terminal voltage of the primary winding reaches a rated value, and recording the terminal voltage, the primary current and the primary input power of the primary winding under different amplitude voltages to determine an no-load characteristic curve of the linear induction motor to be tested;
(5) solving the excitation resistance and the excitation inductance of the linear induction motor to be detected at the preset speed according to the short-circuit characteristic curve and the no-load characteristic curve of the linear induction motor to be detected;
(6) and (5) dragging the primary stage of the linear induction motor to another preset speed, repeating the steps (4) and (5), and obtaining the excitation resistance and the excitation inductance of the linear induction motor to be detected at different preset speeds.
Optionally, the primary of the measured linear induction motor is pulled to a predetermined speed by a power motor.
Optionally, the frequency of the second sinusoidal voltage is determined by the predetermined speed, so that the magnetomotive force generated by the second sinusoidal voltage is opposite to the predetermined speed relative to the primary moving speed, so that the magnetomotive force is 0 relative to the secondary moving speed, and for the secondary without magnetic field cutting, the linear induction motor is in a no-load state, thereby creating an experimental condition for a no-load experiment.
Optionally, assuming that the predetermined speed is V, the frequency of the second sinusoidal voltage is:tau is the primary winding pole pitch of the linear induction motor.
Optionally, the short-circuit characteristic curve or the no-load characteristic curve includes: the terminal voltage of the corresponding primary winding is in relation to the primary current, and the terminal voltage of the corresponding primary winding is in relation to the primary input power.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
(1) the off-line measurement method for the parameters of the linear induction motor provided by the invention comprises the steps of firstly determining a model of the motor according to a T-shaped equivalent circuit, and then measuring short-circuit impedance, rotor resistance and stator and rotor leakage reactance through a locked-rotor experiment. And injecting voltages corresponding to the reverse advancing frequency and the speed into the motor to be detected at different speeds, so that the magnetomotive force formed by the motor to be detected is static relative to the secondary, and the slip is 0, thereby obtaining the sizes of the excitation resistance and the excitation inductance at the speed. The method can solve the motor parameters at each operating speed, takes the actual operating conditions of the motor into consideration, and can obtain higher operating efficiency and higher thrust precision by controlling with the mathematical model.
(2) According to the off-line measuring method for the parameters of the linear induction motor, only sine voltage needs to be injected into a primary stage, and primary current and input power are detected. The method has the advantages that extra hardware cost is not needed in control, in the field of high-power traction, one vehicle comprises a plurality of power compartments, and one power compartment comprises a plurality of inverters and motors, so that the power motor for providing constant speed in the method does not need to be additionally provided, and the method is high in practicability.
(3) The off-line measurement method for the parameters of the linear induction motor provided by the invention does not depend on certain fixed motor parameters and a mathematical model for clarifying the parameter change rule, and can be used as a check standard of other models.
Drawings
Fig. 1 is a schematic structural view of a conventional linear induction motor;
FIG. 2 is a schematic diagram of an edge effect of a conventional linear induction motor;
fig. 3 is a schematic diagram of a T-shaped equivalent circuit of the linear induction motor provided by the present invention;
FIG. 4 is a schematic structural diagram of a no-load test platform of the linear induction motor provided by the invention;
fig. 5 is an equivalent circuit diagram of a locked rotor experiment of the linear induction motor provided by the invention;
fig. 6 is an equivalent circuit diagram of a no-load test of the linear induction motor provided by the invention;
fig. 7 is a flowchart of an offline measuring method for parameters of a linear induction motor according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to fig. 5. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Fig. 3 is a schematic diagram of a T-shaped equivalent circuit of a linear induction motor according to the present invention, as shown in fig. 3,andrespectively phase voltage and phase current vectors,the vector of the secondary current is represented,representing the excitation current vector, Rs、Rr、Lsσ、LrσAre respectively a primary resistance, a secondary resistance, a primary leakage inductance, a secondary leakage inductance, R'r(v) And L'm(v) The excitation resistance and the excitation inductance, respectively, taking into account the end effect, the magnitude of which is related to the velocity v,to reflect the equivalent resistance of the electromagnetic output power, s represents the slip ratio, which is (electrical frequency-primary motion frequency)/electrical frequency.
In a specific embodiment, the invention adopts a mechanical connection of a power motor and a tested linear induction motor to test the no-load characteristic curve of the motor. The power motor is used for providing constant speed, the tested linear induction motor is connected with sine voltage, the figure 4 is a structural schematic diagram of the testing platform of the invention, and the difference of the testing platform from the traditional rotary induction motor is that the resistance and inductance value on the excitation branch of the rotary induction motor are related to the motor running speed and the motor structural parameters, so no-load and short-circuit experiments need to be carried out at different speeds, and the resistance and inductance value on the excitation branch are respectively obtained. Wherein, V represents the linear velocity that the power motor drags the whole system to, VFDuring no-load experiment, the traveling speed and the size of a traveling wave magnetic field generated by sine voltage introduced into the motor to be testedIs the same as V and is opposite to V.
Based on the test platform shown in fig. 4, the parameter offline measurement method provided by the invention comprises the following steps:
(1) and (5) blocking the rotation of the linear induction motor to be detected.
Specifically, the primary linear induction motor to be detected is clamped by a mechanical device, sliding under the action of thrust is prevented, the air gap distance between the primary and secondary stages is ensured to be the same as that in rated operation, the frequency of the primary linear induction motor to be detected is a sine wave with rated frequency and gradually increased amplitude, and the current is close to the rated value. Because of the locked rotor, the primary and the secondary are both static, the slip s is close to 1, and the impedance of the excitation branch is far greater than the impedance of the rotor side, so the excitation branch can be ignored, as shown in fig. 5, fig. 5 is an equivalent circuit diagram of the locked rotor experiment of the linear induction motor, and during the locked rotor experiment, s is 1, and the impedance of the excitation branch is far greater than the impedance of the rotor branch, which can be derived from the equivalent circuit shown in fig. 4.
(2) The primary winding voltage U of the tested motor is recorded after the sine voltage with different amplitudes and the amplitude is gradually increased until the current is close to the rated valuekPrimary current IkPrimary input power PkThe short circuit is plotted and the subscript k indicates a short circuit.
Wherein the short circuit curve comprises: i isk=f1(Uk),Pk=f2(Uk)。f1Representing the voltage U across the primary winding in a short circuit conditionkAnd a primary current IkFunctional relationship of f2Representing the voltage U across the primary winding in a short circuit conditionkAnd primary input power PkThe functional relationship of (a).
(3) The tested motor is dragged into a certain constant speed V by the power motor and is kept constant. Frequency is introduced into the primary of the motor to be measuredThe amplitude of the sine wave is gradually increased, and the generated magnetomotive force has the opposite traveling direction to V. Wherein V is the actual running speed of the motor to be measured, and tau is the primary winding polar distance of the linear induction motor. Due to the primary stage relative toThe secondary movement speed is V, the magnetomotive force is-V relative to the primary movement speed, so the magnetomotive force is 0 relative to the secondary movement speed, the secondary is cut without a magnetic field, the space has a magnetic field, eddy currents are generated at the input end and the output end of the primary, and the side end effect is achieved, so the no-load experimental condition with the side end effect is created. Fig. 6 is an equivalent circuit diagram of a no-load test of the linear induction motor, in the no-load test, s is 0, and the rotor branch impedance is much larger than the excitation branch impedance, which can be derived from the equivalent circuit shown in fig. 4.
(4) The primary of the motor to be measured is charged with sinusoidal voltage which advances reversely and has frequency corresponding to the primary movement speed, the amplitude is gradually increased to be close to a rated value, and the terminal voltage U of the primary winding is recorded0Primary current I0Primary input power P0Drawing a no-load curve; subscript 0 indicates no load.
Wherein the no-load curve includes: i iso=f3(Uo),Po=f4(Uo)。f3Representing voltage U across the primary winding under no-load conditions0And a primary current I0Functional relationship of f4Representing voltage U across the primary winding under no-load conditions0And primary input power P0The functional relationship of (a).
(5) With the short-circuit and no-load equivalent circuits given in fig. 5 and fig. 6, the excitation resistance and the excitation inductance at the speed are solved by using the curves obtained in (2) and (4); the solving principle is consistent with the parameters of the no-load short circuit test for solving the T-shaped equivalent circuit of the common rotating motor, and therefore, the details are not repeated.
(6) And (5) changing the dragging speed of the power motor, and repeating the steps (4) - (5). And (4) judging whether all the parameters on the running speed are measured, if not, changing the dragging speed value of the power motor in the step (3), keeping the speed constant, and repeating the steps (4) to (5) until all the parameters of the excitation resistance and the excitation inductance are measured at all the speeds. Finally obtaining excitation resistance and excitation inductance at each speed to obtain R'r(v) And L'm(v)。
The invention discloses an off-line measuring method for parameters of a linear induction motor. And simultaneously solving the values of all parameters in the equivalent circuit through a no-load experiment and a short-circuit experiment. Due to the structural reason of the linear induction motor, the electromagnetic parameters in the equivalent circuit obviously change along with the operation speed and the structural parameters of the motor due to the edge effect, and the edge effect is more obvious at high speed. In addition, no-load lock-up experiments are easy to perform on conventional rotating induction machines.
However, in a conventional short primary linear induction motor, the primary side where the excitation winding is located is the load of the motor, so that no-load experiments on the linear induction motor which is loaded are difficult to perform. The requirements of the measurement method are as follows: two motors are used, one providing constant speed is called as a power motor, and the other is used for parameter measurement and is called as a measured motor.
The method provided by the invention comprises the following steps: first, the motor to be measured is locked (i.e., movement is prohibited in a linear machine), and a voltage of a rated frequency is applied from the first stage, and the amplitude rises from 0 until the current approaches the rated value. The input power and current versus effective value of applied voltage are recorded. Secondly, the motor to be tested is dragged to a constant speed through the power motor, the primary winding is electrified with reverse advancing voltage, the frequency corresponds to the primary speed, the voltage amplitude gradually rises from 0, and the change curve of the current and the input power is recorded, namely the no-load curve. Under the same speed, the excitation inductance, the excitation resistance and other parameters under the speed can be solved by simultaneously establishing an equation obtained through a no-load experiment and a short-circuit experiment under the speed.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (3)
1. An off-line measuring method for parameters of a linear induction motor is characterized by comprising the following steps:
(1) the primary position of the linear induction motor to be detected is fixed by locking the rotor, so that the linear induction motor to be detected is short-circuited, and the size of an air gap between the primary and secondary is ensured to be unchanged;
(2) introducing first sinusoidal voltages with rated frequency and different amplitudes to the primary side of the short-circuited linear induction motor to be detected, gradually increasing the amplitudes until the primary current reaches the rated value, and recording the terminal voltage, the primary current and the primary input power of a primary winding under different amplitude voltages to determine the short-circuit characteristic curve of the linear induction motor to be detected;
(3) dragging the primary side of the linear induction motor to be detected to a preset speed through a power motor, wherein the preset speed value is within a traveling speed range when the primary side of the linear induction motor works;
(4) after the primary is dragged to a preset speed, introducing a second sinusoidal voltage which advances in the reverse direction and has a frequency determined by the preset speed into the primary of the linear induction motor to enable the linear induction motor to be tested to be in no-load, gradually increasing the amplitude of the second sinusoidal voltage until the terminal voltage of the primary winding reaches a rated value, and recording the terminal voltage, the primary current and the primary input power of the primary winding under different amplitude voltages to determine an no-load characteristic curve of the linear induction motor to be tested; setting the preset speed as V, wherein V is the actual running speed of the measured linear induction motor; the frequency of the second sinusoidal voltage is:tau is the primary winding polar distance of the linear induction motor;
(5) solving the excitation resistance and the excitation inductance of the linear induction motor to be detected at the preset speed according to the short-circuit characteristic curve and the no-load characteristic curve of the linear induction motor to be detected;
(6) and (5) dragging the primary stage of the linear induction motor to another preset speed, repeating the steps (4) and (5), and obtaining the excitation resistance and the excitation inductance of the linear induction motor to be detected at different preset speeds.
2. The method of claim 1, wherein the frequency of the second sinusoidal voltage is determined by the predetermined speed, such that the magnetomotive force generated by the second sinusoidal voltage is opposite to the predetermined speed relative to the primary speed, such that the magnetomotive force is 0 relative to the secondary speed, such that the linear induction motor is unloaded when no magnetic field is applied to the secondary.
3. The method of offline measurement of parameters of a linear induction motor according to any of claims 1 to 2, characterized in that said short-circuit or no-load characteristic comprises: the terminal voltage of the corresponding primary winding is in relation to the primary current, and the terminal voltage of the corresponding primary winding is in relation to the primary input power.
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CN113965124B (en) * | 2021-10-12 | 2023-11-21 | 中国科学院电工研究所 | Parameter calculation method of linear induction motor |
CN116068395B (en) * | 2023-03-07 | 2023-06-13 | 中国科学院电工研究所 | Parameter testing method of linear induction motor in static state |
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