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Atv71 Protection Settings


jsl

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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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motor thermal protection setting on a ATV71 is set to 118%

Where does this figure / recommendation come from?

 

Best regards,

Mark.

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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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