Energy-efficient operation of induction motors and power quality standards

• Induction motors are usually significantly underloaded and work inefficiently.
• Modification of power quality standards leads to more efficient motor operation.
• The appropriate power quality recommendations are elaborated.
• Results of power quality monitoring are presented.

Induction motors are usually considerably oversized and consequently often work inefficiently because of various factors such as the relatively poor voltage quality that is allowed in public and industrial networks. A possible solution is the amendment of power quality rules. This paper presents a preliminary proposal to modify the power quality standards: EN 50160 Voltage characteristics of electricity supplied by public distribution network and EN-ICE 61000-2-4 Electromagnetic compatibility (EMC) – Part 2–4: Environment – Compatibility levels in industrial plants for low-frequency conducted disturbances. The proposal consists of a complete set of power quality indices with simplified temperature coefficient of power quality, the value of which corresponds to the windings temperature rise of induction machines with decreased supply voltage quality. The recommended limit values for the coefficient are determined according to an analysis of various cases of induction machine heating. Additionally, the results of the factor monitoring in actual power systems are presented.