Danfoss TTS700

4.29 Magnetic Bearings
4.29.1 Magnetic Bearings Function
Thecompressorshaftandimpellerslevitateduringoperationandfloatonamagneticcushioncreatedbythe
magneticbearings.Permanentmagnetsdomostoftheworkandelectromagnetsareusedfortrimmingtheshaft
positionwithin0.0003”(7microns).Oneaxial(Zaxis)andtworadial(X&Yaxis)magneticbearingsareusedto
maintainshaftposition.Centeredrotationisinstantaneouslyself-correctedandmaintainedbythebearingcontrol
loop.RefertoFigure4-252BearingControlSignalFlowonpage226.
Whennotpowered,theshaftissupportedbycarboncompositeorrollertouchdownbearings.
4.29.2 Magnetic Bearings Connections
PWMconnectorssupplypoweratthebearingpowerfeedthroughs.RefertoFigure4-255BearingConnections.
Figure 4-255 Bearing Connections
4.29.3 Bearing Verification

4.29.3.1 Bearing Coil Verification

• • • CAUTION • • •
Donotattempttoperformaninsulation(megger)testonacomponentundervacuum.Thiscancauseinsulationbreakdownorfailure
duringthetestingprocess.

NOTE
l
Tocheckbearingcoilinsulationintegrity,aMegaohmmeter(e.g.,Megger)setto1KVshouldbeused.Readingsfromcoils
togroundshouldbegreaterthan100MΩ,andreadingsbetweencoilsshouldbegreaterthan100MΩ.
l
AfaultyPWMAmplifiermaybetheresultofabearingfailureandmaycauseafailureofthePottedDC-DCConverter
resultinginablownF1fuseontheClosedTopSoftStart.Ifabearingcoilisfoundtobefaulty,thenthePWM,PottedDC-DC
Converter,andClosedTopSoftStartF1fusemustbeverifiedaswell.

Page 230 of 294 - M-SV-001-EN Rev. H 1/23/2023