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A kind of motor thermal overload protection method

A technology for electric motors and thermal overload, applied to emergency protection circuit devices, electrical components, etc., can solve problems such as difficult handling, errors, and increased calculations, and achieve the effects of simple and easy implementation, stable and reliable algorithms, and simple calculations

Active Publication Date: 2016-08-17
BEIJING SIFANG JIBAO AUTOMATION +1
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Problems solved by technology

But the actual situation is that the load current of the motor is often variable. In this case, it is difficult to directly determine the tripping time of the thermal overload protection by using formula (1)
[0009] (c) Formula (1) contains a logarithmic function, which is difficult to handle
It is often necessary to use some approximate algorithms such as Taylor expansion and curve fitting to calculate the logarithmic function, which causes a certain degree of error and increases the amount of calculation

Method used

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  • A kind of motor thermal overload protection method
  • A kind of motor thermal overload protection method
  • A kind of motor thermal overload protection method

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Embodiment Construction

[0033] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0034] as attached figure 1 As shown, a three-phase current transformer is installed on the motor power supply line. The motor protection device obtains the three-phase current of the motor from the secondary side of the three-phase current transformer.

[0035] As mentioned in the background technology, the national standard GB / T 14598-15-1998 of the People's Republic of China for electric thermal relays stipulates that the thermal characteristics of the motor thermal overload protection are as follows:

[0036] t = τ ln I 2 - I P 2 I 2 - ( k ...

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Abstract

The invention discloses a motor thermal overload protection method, which includes the following steps: (1) collecting the load current of the motor, and calculating the equivalent current I eq ; (2) Calculate the heat accumulation value of the motor at the current moment Among them, θ *k is the heat accumulation value of the motor at the current moment, θ *k‑1 is the heat accumulation value calculated last time; I *k is the equivalent current I at the current moment eq and starting current setting I set τ is the motor heating time constant, Δt is the calculation time interval; (3) when the heat accumulation value θ *k When p is reached, the thermal overload protection will alarm, among them, 0 <p<1；（4）当热积累值θWhen *k reaches 1, the thermal overload protection outlet trips. This method can take into account the heat accumulation of the motor before thermal overload, and can better reflect the thermal overload state of the motor. It has the advantages of simple calculation, stable and reliable algorithm, and simple and easy implementation.

Description

technical field [0001] The invention belongs to the technical field of relay protection, and in particular relates to thermal overload protection of a motor. Background technique [0002] The national standard GB / T 14598-15-1998 of the People's Republic of China for electric thermal relays specifies the thermal characteristics of thermal overload protection for motors as follows: [0003] t = τ ln I 2 - I P 2 I 2 - ( k * I B ) 2 - - - ( 1 ) ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/085
Inventor 董杰李继晟苏毅朱启晨邹卫华秦应力杨志贤刘全
Owner BEIJING SIFANG JIBAO AUTOMATION
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