Non-intrusive induction motor speed detection

This paper presents an algorithm that enables estimation of the speed of a single induction motor in an aggregate current signal supplying several motors from a common utility feed. This algorithm maintains accuracy of speed estimation while using shorter lengths of data, and can distinguish the activation of individual motors in the aggregate signal. The ability to separate and track distinct motor harmonics in an aggregate current signal opens the door to non-intrusive energy scorekeeping and diagnostics for systems like air conditioning that operate under closed-loop control. New experimental results demonstrate the approach for these air-conditioning components in real buildings.