ON THE ENERGY OPTIMIZED CONTROL OF STANDARD AND HIGH-EFFICIENCY INDUCTION-MOTORS IN CT AND HVAC APPLICATIONS

This paper contains an analysis of hew the choice of energy optimal co ntrol of induction motors is influenced by motor construction, standar d versus high-efficiency motor, and by application, constant torque (C T) and heating, ventilation, and air conditioning (HVAC) (interpreted as vector and scalar motor drives). The analysis is made with a 2.2-kT Y voltage-source-inverter-fed squirrel-cage motor drive as an example throughout the paper, but through statistics on the use of motors and their efficiencies, the conclusions are widened to a broader range (0- 50 kW), Energy optimal control strategies are reviewed and cos(phi) co ntrol, a model-based control, and a search control are implemented in the laboratory in a vector and a scalar motor drive. The convergence s peed for the strategies and their ability to reject disturbances are i nvestigated by experiments, It is also shown experimentally that, for both standard and high-efficiency motors, motor energy-efficiency impr ovement is;achievable by energy optimal control below 60% load torque, The energy savings using energy optimal control strategies are measur ed on a pump system with a certain load cycle. Model-based control is recommended for CT applications and cos(phi) control for HVAC applicat ions.