Thermal derating of TEFC induction motors coated or partially flooded by spilled pulp

Abstract

Induction motors driving the agitators in pulp tanks are affected by the leakage of pulp that coats their inter-fin channels, blocks the air inlets of the fan cover, or partially floods them. This paper presents a complete thermal evaluation of TEFC induction motors during these abnormal conditions. A totally enclosed fan cooled (TEFC) induction motor fitted with 12 thermocouples was tested in the different situations of interest, including pulp spilled over the frame, in the air intake, and partially flooding it. Winding, frame, and bearing temperatures were measured. These results are used to determine the required oversizing of an agitator motor in order to assure that the motor will not fail even if the inter-fin channels become obstructed with spilled pulp.