Phase Advancer

During starting or low load condition IM works on very lagging current which results in taking high current.
This sudden high current may creats transient in power system, which is undesirable.
Phase advancer donot let current lag too much and protects from transient.

Now real question "Why Phase Advancer is not used in below 200kva machine?"
-Because lesser kva machine won't take that much current even in worsed condition which causes transient or surge or votage drop. so we do not care for lesser machine.
But more than 200kva machine will take vry heavy current causing many problem mentioned above.