Large Size VFD Performance Analysis

VFD performance measurements are a critical part of commissioning today’s modern large scale variable speed motors and validation as to long term use acceptability.

A specialized data acquisition system has been developed by EDI to measure and monitor power quality in plant grid power or on multi-phase systems (3, 6, 12, or more phases). These parameters include phase currents, line-to-line voltages, input and output current, and output voltage harmonic profiles. For low frequency applications (below several orders of motor electrical frequency), data can be obtained directly from existing PTs and CTs with minimal disturbance to the system.  Alternatively, high voltage probes can be attached directly to the motor bus bars or incoming power grid, and phase corrected Rogowski coil flexible current probes can be installed around power cables to obtain high frequency data (up to 10 kHz). Measurement of these parameters during operation of the equipment facilitates evaluation of dynamic and static torque, real and reactive power components, and efficiency.