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Fan Control

Resonant Speed

Identiﬁcation Procedure

•

Asstatedpreviously,whenadjustingtheVFDspeed,proceedslowlywhilemonitoring

thevibrationlevels.Ifthevibrationvalueapproaches0.35ips(0-peak),slowly“zero

in”onthespeedwherethevalueequals0.35ips,andrecordthespeedatwhichthis

occursasthelowerendofthelockoutrange.Alsorecordthevibrationlevelatthis

speed.

• Continuetoslowlyincreasethespeedwhilemonitoringthevibrationlevel.Ifthisisa

resonance,thenthevalueshouldpeakandeventuallydecreasetoalevelthatisbelow

0.35ipsasthespeedisincreased.Afterthevibrationlevelhaspeakedandcontinues

tofall,recordthespeedwherethevalueequals0.35ipsastheupperendofthe

lockoutrange.

• Usingthisdata,abaselineforvibrationhistorycanbedeveloped.Thevibrationlevels

canbemonitoredyearlyandthetrendusedtoindicatepotentialwearortheneedto

replacecomponentsinthedrivesystem.

• Aftertheentirespeedrangehasbeencheckedandanyresonancesidentied,ensure

theVFDthatcontrolsthefanmotoristhenturnedoff,andthepowertothemotor

circuitislockedout.

• Entertheunit,andcarefullyremovetheaccelerometer,alongwithanyassociated

wiringfromtheunit.

• WorkwiththeVFDcontractortoenterthelockoutspeedrangesintotheVFD,sothe

unitwillnotoperateataresonantspeed.

• Onceithasbeenveriedthatthedrivesystemisallclear,returntheunittoitsnormal

operatingcondition.

• Keeparecordofanylockoutspeedrangesforfuturereference.

BAC 3358C User Manual

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