User manual 09/2009 - Schneider Electric

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User manual 09/2009 - Schneider Electric

The Protection FunctionUnderload Motor ProtectionPresentationUnderload motor protection provides additional protection for detection of motor no-load operation.Examples of no-load operation: pump running dry, broken drive belt, broken geared motor, etc.DescriptionUnderload motor protection compares the value of the phase current minimum I MIN with the settingvalue of the protection Iund pick-up. If the current value I MIN falls below the Iund pick-up, the protectiontund time delay is actuated.By default, underload motor protection is not active.After parameter setting, underload protection is activated during startup and in steady state.Operating PrincipleThe figures below illustrate the operating possibilities:Diagram Diagram 1 Motor current2 Supervision by underload motor protectionWhite: Not active; Green: Active• Diagram Ι: The phase current minimum value I MIN does not go above the protection Iund pick-upbefore the end of the tund time delay (for example, a pump operating at no load). Underload motorprotection trips:• A: Protection activated (change to steady state)• B: Activation of protection time delay as soon as the pick-up threshold is crossed• C: Protection tripped at the end of the time delay• Diagram ΙΙ: The phase current minimum value I MIN goes back and stays above the pick-up beforethe end of the tund time delay (for example, a pump temporarily running dry). The underload motorprotection does not trip:• B: Activation of protection time delay as soon as the pick-up threshold is crossed• D: Protection disabledNOTE: The SDTAM module early tripping protection function can be used to command contactor opening(see SDTAM Module Option, page 57).Setting the ProtectionThe Iund pick-up and the tund time delay settings can only be accessed by the communication optionusing the RSU software (see Protection parameter setting, page 121).Iund Pick-Up Setting ValueThe Iund pick-up setting value is expressed in multiples of Ir.The pick-up setting range is: 0.3...0.9 Ir. The step is 0.01 Ir. The default setting is OFF: protection notactive.The accuracy range is +/- 10%.tund Time Delay Setting ValueThe tund time delay setting value is expressed in seconds.The time delay setting range is: 1...200 s. The step is 1 s. The default setting value for the time delay is10 s.70 LV434104 09/2009

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