Historically, expensive voltage varying equipment such as multiple tap transformers or saturable reactors were recommended for all but the very low temperature applications.

• 该产品的电阻值在其有效使用期限内；阻值是逐渐变大.；因此；某种程度上来讲；保持管内输入功率能量或者是熔炉的温度足够高是必须的