Temperature rise in induction motor windings as the cause of variation in rotational speed of an axial fan

Abstract

The paper presents results of an experimental investigation performed under controlled laboratory conditions, in order to identify real causes of variation in the rotational speed of an axial fan that can be noticed after a certain period following the start of operation. The theoretical background important for understanding the observed phenomenon is given and the hypothesis is proposed which states that the temperature rise in motor windings and a consequential rise of their resistances are responsible for such specific behavior of the axial fan. The experiment was performed on a standard test rig with a small industrial axial fan, driven by a three-phase induction motor with the rated power of 1.5 kW. The experimental procedure is described in details, measured and calculated results are presented and appropriate conclusions are given. The obtained experimental results confirm the proposed hypothesis.

Development of a Starter with Protective Systems for a Three-Phase Induction Motor

“…As a result, the National Electrical Manufacturers Association established permissible operating temperature limits depending on classes (Y, A, E, B, F, and H) of insulation of the stator winding [9]. Contemporary motors were reported to be produced in the F tolerance class in [10].…”

“…e fan was powered via a Triac (BT136). e gate of the Triac was triggered through (IC2) a Diac-LED optocoupler (MOC3010) [10]. e light-emitting diode section was powered by a voltage controlled oscillator (VCO) configured using the monolithic 555-timer integrated circuit connected in the astable mode (free-running oscillator) with frequency (f ) given in [15] as…”