Motor Protection Principles.pdf

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Overload Curve Selection If the motor starting current begins to infringe on the thermal damage curves or if the motor is called upon to drive a high inertia load such that the acceleration time exceeds the safe stall time, custom or voltage dependent overload curve may be required. 16
Overload Curve Selection A custom overload curve will allow the user to tailor the relay’s thermal damage curve to the motor such that a successful start can occur without compromising protection while at the same time utilizing the motor to its full potential during the running condition. 17
Page 1 and 2: Motor Protection Principles Craig W
Page 3 and 4: Various Industry Motor Applications
Page 5 and 6: Thermal Stress Causes Motor Failure
Page 7 and 8: Motor Electrical Protection • The
Page 9 and 10: Thermal Model - Motor States • Mo
Page 11 and 12: Thermal Overload Pickup • Set to
Page 13 and 14: Overload Curve Selection for Therma
Page 15: Hot/Cold Safe Stall Ratio HCR = LRT
Page 19 and 20: Thermal Model - Current Unbalance B
Page 21 and 22: Thermal Model - RTD Bias • Accele
Page 23 and 24: Overvoltage Protection • The over
Page 25 and 26: Unbalance Protection • Indication
Page 27 and 28: Ground Fault Protection Zero Sequen
Page 29 and 30: Differential Protection • Differe
Page 31 and 32: Differential Protection Biased diff
Page 33 and 34: Stator RTD Protection • A simple
Page 35: Conclusions • Induction & synchro

Motor Protection Principles.pdf

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