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electrical-engineering-portal.com htt p:/ /elec tri cal-engineering-po rtal.co m/stator-o verheat ing-pro tection Stator Overheating Protec tion (on photo b ottom of the Motor Stator Winding; by ele ctrical-f ore nsics.co m) Edvard Stator Overheating Protection Overheating All m o t ors need pro t ect io n agains t o verheat ing res ult ing f rom overload , stalled rotor , or unbalanced stator currents. For complete prot ection, t hree-phase motors should have an overload element in each phase . This is because an open circu it in the s uppl y to the po wer transf ormer f eedi ng a motor wil l cause t wic e as muc h current t o f low i n one phase of the mot or as in either of the ot her two pha ses, as shown in Figure 1. Consequently , to be sure t hat t here wi ll be an overl oad element in t he mos t heavily l oaded phase no ma tt er whi ch power-t ransf ormer phase is o pen-circuited, one should provide overload elements in all three phases. I n spite of the desirabi lity of overload ele ments in all three phases, mot ors rated about 1500 hp and below are generall y provided with elements in only two phases, o n the ass umption t hat t he open-phase co ndition wil l be detected and corrected bef ore any m ot or can overhea t .
