Motor Protection Principles.pdf

More documents

Recommendations

Info

Risks for an Overheated Motor • Stator Windings Insulation Degradation (for stator limited motors) Insulation lifetime decreases by half if motor operating temperature exceeds thermal limit by 10ºC for any period of time 110 PERCENTAGE OF LIFE (%) 100 90 80 70 60 50 40 30 20 10 A-CLASS (105 ºC) B-CLASS (130ºC) F-CLASS (155 ºC) H-CLASS (180 ºC) A B F H For F class insulation, stator temperature of 165ºC causes motor lifetime to decrease to 50% 0 0 50 100 150 200 250 300 TEMPERATURE (ºC) • Rotor Conductors Deforming or Melting (for rotor limited - thermal limit is defined by motor stall time) 6
Motor Electrical Protection • Thermal Overload • Process Caused (Excessive load) • High Ambient Conditions (Hot, Blocked Ventilation) • Power Supply Issues (Voltage/Current Unbalance, Harmonics) • Phase Fault • Ground Fault • Abnormal Operating Conditions • Over & Under Voltage • Underfrequency • Voltage and Current Unbalance • Load Loss • Jamming • Jogging 7
Page 1 and 2: Motor Protection Principles Craig W
Page 3 and 4: Various Industry Motor Applications
Page 5: Thermal Stress Causes Motor Failure
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 and 16: Hot/Cold Safe Stall Ratio HCR = LRT
Page 17 and 18: Overload Curve Selection A custom o
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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?