区别就是两者意思是不一样具体的不同如下

increase to中文意思是增加到……

While welding current increase to a threshold the arc will not go out.

焊接电流增加到一定值时，就可消除熄弧和再引弧现象，使工频正弦交流TIG电弧也具有良好的电弧稳定性。

increase by中文意思是增长百分之……;

例句

The Bureau of Labor Statistics projects that while the number of nurses will increase by 19 percent by 2022, demand will grow faster than supply, and that there will be over one million unfilled nursing jobs by then.

劳工统计局预计，虽然到2022年护士人数将增加19%，但需求增长将快于供给，届时将有100多万个空缺的护理岗位。