Power device over-temperature protection method based on temperature curve slope control

Abstract

The invention discloses a power device over-temperature protection method based on a temperature curve slope control. The method comprises the following steps: a negative temperature coefficient (NTC) thermistor is added on a radiator outside a power device in an inverter and the initial temperature of the NTC thermistor can be detected when the inverter is powered on; 2) an average slope value K1 of a temperature variation curve of the NTC thermistor in an inverter operation nT time segment when the temperature value relative environment temperature of the NTC thermistor exceeds 20 DEG C is obtained after the inverter is operated, 3) in the same way, an ith nT time segment Ki is obtained; (4) when ki is not more than 1, the normal operation of a fan is judged, and an over-temperature protection set value is an over-temperature protection default value; when Ki is more than 1 for many times continuously, non-operation of the fan is judged, and the over-temperature protection set value is lowered; (5) Once the temperature of the NTC thermistor exceeding the over-temperature protection set value is detected, the inverter produces an over temperature protection fault, a PWM (Pulse-Width Modulation ) output is blockaded , and a motor is freely halted. The power device over-temperature protection method effectively solves the problem of over-temperature protection reliability, and also can judge whether the fan is operated normally or not.

Description

technical field [0001] The invention relates to a power device over-temperature protection method based on temperature curve slope control, which is applied to all power devices for temperature protection based on NTC thermistors. Background technique [0002] In the process of inverter product development, power devices such as IGBTs or thyristors are often used. Power devices pass through higher voltage and larger current during operation, coupled with higher carrier frequency, and are the largest components of inverter products. The heat source, the temperature rise is relatively high, the reliability of the power device directly determines the reliability of the entire frequency converter, if the heat dissipation is not good, it will directly lead to the damage of the power device, so the power device must be increased in the actual application. temperature protection function. [0003] There are two main methods of traditional power device over-temperature protection: ...

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Problems solved by technology

[0004] However, the above two methods have certain disadvantages: 1. The disadvantages of the former are mainly reflected in the fact that some power devices do not have temperature detection inside. Only after the optocoupler is isolated can it be sent to the CPU for processing, which will increase the complexity of the circuit design; 2. The disadvantage of the latter is mainly reflected in the fact that there is a certain distance between the external NTC thermistor and the hottest point of the power device, resulting in a temperature difference between the two There is a greater relationship with the heat dissipation material of the radiator, especially when the temperature of the power device rises sharply, due to the limitation of the heat transfer speed, the heat transfer has a process, and there is a lag, so that the temperature difference between the two will be greater. Large, in some working conditions, if the temperature of the power device rises sharply, the protection is still performed according to the fixed over-temperature protection point at this time, which may cause the over-temperature protection to fail

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