Performance of a variable-speed inverter/motor drive for refrigeration applications

Presents the results of an experimental investigation into the application of inverter-based variable-speed drives to positive displacement rotary vane refrigeration compressors. The investigation considers the effects of the inverter on a number of operating parameters such as the harmonic currents and voltages on both the supply side and motor side, power consumption and power factor, starting current and overall system efficiency. The results indicate that the use of off-the-shelf inverters for variable-speed control of refrigeration compressors can inject harmonics to the supply system which exceed the maximum limits imposed by BS5406. The inverter may also cause a reduction in the power factor and in the overall efficiency of the drive. Variable-speed operation of a rotary vane compressor may not offer efficiency advantages over fixed-speed operation but can provide other benefits such as better temperature control and faster response to sudden changes in load.<>