Time constant measurement for control of induction heating processes for thixoforming
Time constant measurement for control of induction heating processes for thixoforming
复制标题
用于控制触变成型感应加热过程的时间常数测量
DOI：
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复制
发表时间：
2015
期刊：
影响因子：
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通讯作者：
Alexander Verl
中科院分区：
文献类型：
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作者：
O. Gerlach;A. Lechler;Alexander Verl
在控制感应加热系统中，存在多种测量方法用于将金属坯锭受控加热至半固态以进行触变成形。最常见的方法是测量坯料温度，其具有导致过程稳定性困难的各种缺点。主要缺点是工艺窗口的温度范围小以及温度和液体分数之间的相关性的合金成分依赖性。另一种方法是通过测量载荷的时间常数来确定坯料的液体分数。虽然时间常数测量不受上述问题的影响，但很难将其用作受控变量。本文指出，影响时间常数测量的干扰主要是由逆变器内部的半导体损耗引起的。介绍了一种补偿这些损失的方法。该方法在感应加热单元的嵌入式系统中实现和测试，从而表明可以使用时间常数测量来确定感应加热期间坯料的液体分数。
In controlling induction heating systems, several measurement methods exist for controlled heating of metal billets into the semi-solid state for thixoforming. The most common approach is to measure the billet temperature, which suffers from various drawbacks leading to difficulties in process stability. The main disadvantages are the small temperature range of the process window and the alloy composition dependency of the correlation between temperature and liquid fraction. An alternative is to determine the liquid fraction of the billet by measuring the time constant of the load. Although time constant measurement is not affected by the mentioned problems, it is difficult to use it as a controlled variable. This paper shows that disturbances affecting time constant measurement are mainly caused by semiconductor losses inside the inverter. A method is introduced to compensate these losses. This method was implemented and tested in the embedded system of an induction heating unit, thereby showing that it is possible to use time constant measurement to determine the liquid fraction of a billet during induction heating.