AC motor unbalanced protection method based on unbalanced accumulation
An AC motor and balance technology, applied in emergency protection circuit devices, electrical components and other directions, can solve the problems of motor damage, the processing of delay time cannot be accurately reflected, and the motor unbalance protection action is inaccurate, so as to improve the protection accuracy. Effect
Inactive Publication Date: 2008-02-13
XIAN UNIV OF TECH
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Problems solved by technology
[0002] Three-phase unbalance is a problem often encountered in the operation of AC motors, which often causes damage to the motor and affects production
In this method, since the judgment is only made at the unbalance level, the processing of the delay time between the unbalance levels cannot be accurately reflected, resulting in inaccurate motor unbalance protection actions
Method used
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[0050] According to the motor tripping time required under different unbalance levels, the Dc(i) value of each unbalance level point can be calculated by formula (1). As shown in Table 1:
[0051] Then: Dc(10)=6400*2 / ((10 2 -9 2 )*1800)=0.37
[0052] Dc(20)=6400*2 / ((20 2 -9 2 )*420)=0.095
[0053] When 10imb ≤20:
[0054] Dc(x)=0.37-0.027(D imb -9)
[0055] Table 1:
[0056] Level: i
[0057] According to this table, the linearization equation of the adjustment parameter Dc between each grade can be calculated and written, and then the adjustment parameter Dc(x) can be calculated.
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The invention discloses an alternating current dynamo imbalance protection method based on unblanced accumulation. The method is conducted according to the following steps. Firstly, three-phase load current of an alternating current dynamo is collected, and the unbalancedness at the moment is figured out. Unbalancedness accumulation coefficients between grade points corresponding to unbalancedness are counted; accumulated dynamo unbalancedness increment of the dynamo within specified time and accumulated value of unbalancedness of the current time are calculated, respectively by using corresponding accumulation coefficients of all points; the accumulation value of unbalancedness of the current time is compared with the set threshold of strip to determine whether the stripping relay is triggered and to protect the dynamo. The invention method adopts the unbalancedness accumulation model to prevent the dynamo from imbalance; and piece-wise linearization method is adopted to adjust the unbalancedness accumulation coefficient DC dynamically, and imbalance protection precision of the alternating current dynamo is significantly improved.
Description
technical field [0001] The invention belongs to the technical field of AC motor protection, and relates to an unbalance protection method of an AC motor. Background technique [0002] Three-phase unbalance is a problem often encountered in the operation of AC motors, which often causes damage to the motor and affects production. At present, the unbalance protection of the motor usually uses a direct discrimination method, that is, according to the motor reaching a certain unbalance level, the motor is tripped and protected by delaying the corresponding time. In this method, since the judgment is only made at the unbalance level, the processing of the delay time between the unbalance levels cannot be accurately reflected, resulting in inaccurate motor unbalance protection actions. Contents of the invention [0003] The object of the present invention is to provide an AC motor unbalance protection method based on the accumulation of unbalance degree. The method adopts the m...
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IPC IPC(8): H02H7/08
Inventor 孙旭霞李生民钟彦儒
Owner XIAN UNIV OF TECH
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