Transcription of Motor Protection - Electrical Sector
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133 2005 Cooper BussmannFor Summary of Suggestions to Protect Three-Phase Motors AgainstSingle-Phasing see the end of this section, page , the causes of Motor failure can be attributed to:Overloads30%Contaminants19%Single-pha sing14%Bearing failure13%Old age10%Rotor failure5%Miscellaneous9%100%From the above data, it can be seen that 44% of Motor failure problems arerelated to a Motor to reach and operate at a temperature 10 C above its maximum temperature rating will reduce the Motor s expected life by 50%.Operating at 10 C above this, the Motor s life will be reduced again by 50%.This reduction of the expected life of the Motor repeats itself for every 10 is sometimes referred to as the half life there is no industry standard that defines the life of an electric Motor ,it is generally considered to be 20 term, temperature rise , means that the heat produced in the Motor windings (copper losses), friction of the bearings, rotor and stator losses (corelosses), will continue to
134 ©2005 Cooper Bussmann How to Calculate Voltage Unbalance and The Expected Rise in Heat Motor Protection Voltage Unbalance & Single-Phasing Phase A Phase B Phase C 248 Volts
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