I recommend you put a power quality analyzer on this circuit and watch the response when the elevator operates. That will help you narrow down the problems. If it's just a matter of the elevator frequency drive creating so much ITHD that VTHD is tripping this breaker, you're going to have other problems that go far beyond a nuissance trip and really need to bring the THD down. You can't know any of this, though, until you get some instrumentation on there.
