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Atv71 Protection Settings, thermal protection |
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 Sep 17 2009, 07:33 AM
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#1
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Junior Member  Group: Members Posts: 3 Joined: 14-September 09 Member No.: 6,526  |
could someone please explain why the motor thermal protection setting on a ATV71 is set to 118%
where does this figure come from? if this is an allowance for service factor of the motor which i understood to be 115% am i right in assuming that anything above 100% contributes to a shorter motor life? is this the equivilent of other manufactures 100% setting (eg GE369 MM2 etc) who quote 100% thermal should be the trip? |
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Sep 17 2009, 10:19 AM
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#2
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Posting Freak Group: Moderator Posts: 2,336 Joined: 24-April 02 From: Christchurch, New Zealand Member No.: 1 |
QUOTE motor thermal protection setting on a ATV71 is set to 118% Where does this figure / recommendation come from? Best regards, Mark. -------------------- Mark Empson administrator
Skype Contact = markempson | phone +64 274 363 067 LMPForum | LMP Tech Warehouse | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | LMP Software | Mark Empson Website |
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Sep 18 2009, 04:44 AM
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#3
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Junior Member Group: Members Posts: 3 Joined: 14-September 09 Member No.: 6,526 |
QUOTE (marke @ Sep 17 2009, 06:19 PM)  Where does this figure / recommendation come from? Best regards, Mark. from the ATV71 programming manual "tHt- b [MOTOR THERMAL PROT.] Note: A fault trip will occur when the thermal state reaches 118% of the rated state and reactivation will occur when the state falls back below 100%." this isnt an obscure parameter, this is the main motor protection. It appears that the ATV71 motor thermal protection is set by default (and cannot be changed) to 118% of the motor thermal state which is calculated by the drive using frequency, time, current, cooling method and an ambient of 40 degrees this i am told by schnieder complies with IEC947-4 however this doesnt answer my question to them Q Although the motor may be protected from short term burnout, would running a motor above 100% but below the trip point (118%) decrease the motors life. i realise this could be achieved by reducing the Motor Thermal setting ITH to 85% of the motor nominal current as opposed to the programming manual which states "Motor thermal protection current, to be set to the rated current indicated on the nameplate". i would still like to understand the reasoning behind th 118% and how it compares with other motor protection relays which state 100% |
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