User manual 09/2009 - Schneider Electric

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User manual 09/2009 - Schneider Electric

The Protection FunctionJam Motor ProtectionPresentationJam motor protection provides additional protection in order to:• Detect overtorque• Monitor mechanical failure• Detect malfunctions more quickly on machines for which the motor is oversizedExamples of machines with a significant risk of jamming: conveyors, crushers and kneaders, fans, pumpsand compressors, etc.DescriptionJam motor protection compares the value of the average motor current Iavg with the setting value of theprotection Ijam pick-up. If the average motor current Iavg exceeds the Ijam pick-up, the protection tjamtime delay is actuated.By default, jam motor protection is not active.After parameter setting, jam motor protection is:• Active in steady state• Disabled during startupOperating PrincipleThe figures below illustrate the operating possibilities:Diagram Diagram 1 Motor current2 Monitoring by jam motor protectionWhite: Not active (startup); Green: Active (steady state)• Diagram Ι: The average motor current Iavg does not fall back below the protection Ijam pick-up beforethe end of the tjam time delay (jammed motor). Jam motor protection 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 average motor current Iavg falls back and stays below the protection Ijam pick-upbefore the end of the tjam time delay (occasional overload). Jam motor protection 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 Ijam pick-up and the tjam time delay can be set as follows:• On the Micrologic trip unit, set on the keypad• Via the communication option using the RSU softwareIjam Pick-Up Setting ValueThe Ijam pick-up setting value is expressed in multiples of Ir.The pick-up setting range on the keypad is: 1...8 Ir. The step is 0.1 Ir. The default setting value is OFF:protection not active.The accuracy range is +/- 10%.68 LV434104 09/2009

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