User manual 09/2009 - Schneider Electric

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User manual 09/2009 - Schneider Electric

The Protection FunctionOperating PrincipleThe figures below illustrate the operating possibilities:Diagram Diagram Diagram 1M Motor current1D Maximum unbalance of the motor phase currents2A Monitoring by phase unbalance protection during startup (diagram I)2B Monitoring by phase unbalance protection in steady state (diagrams II and III)White: Not active; Green: Active• The current unbalance does not fall below the Iunbal pick-up before the end of the tunbal time delay:the phase unbalance protection trips. The behavior of the protection differs according to the motoroperating conditions:• During startup (diagram I)A: Activation of startupB: Activation of protection time delay as soon as the pick-up threshold is crossedC: Protection tripped at the end of the fixed time delay of 0.7 s.• In steady state (diagram II)A: Activation of startupB: Activation of protection time delay as soon as the pick-up threshold is crossedC: Protection tripped at the end of the adjustable time delay• The current unbalance falls below the Iunbal pick-up before the end of the tunbal time delay. the phaseunbalance protection does not trip (diagram III):• B: Activation of protection time delay as soon as the pick-up threshold is crossed• D: Deactivation of protectionNOTE: The SDTAM module early tripping protection function can be used to command contactor opening(see SDTAM Module Option, page 57).Setting the ProtectionThe Iunbal pick-up and the tunbal time delay can be set as follows:• On the Micrologic trip unit, set on the keypad• Via the communication option using the RSU softwareIunbal Pick-Up Setting ValueThe Iunbal pick-up setting value is expressed as a % of the average current.The pick-up setting range on the keypad is: 10...40%. The step is 1%. The default pick-up setting valueis 30%.The accuracy range is +/- 10%.tunbal Time Delay Setting ValueThe tunbal time delay setting value is expressed in seconds.The tunbal time delay setting depends on the operating conditions:• During startup, the value of the time delay cannot be adjusted and equals 0.7 s.• In steady state, the setting range is: 1...10 s. The step is 1 s.The default time delay setting value is 4 s.LV434104 09/2009 67

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