Danfoss TTS350

4.28.3.1 Verify if the Bearing PWM Amplifier is Draining Energy
1. RemovetheServiceSideCover.RefertoSection4.1.3.1ServiceSideCoverRemovalandInstallationon
page54.
2. Disablecompressoroperationwhilekeepingthecompressorenergized.
3. MeasureandrecordthevoltageattheHV+,+17HV,and+5VtestpointsontheBackplane.
4. Isolatecompressorpower.
5. WaitfortheLEDsontheBackplanetoturnoff.
6. Disconnecttherear/axialbearingcurrentoutputcableandthefrontbearingcurrentoutputcable.
7. Applypowertothecompressor.
8. MeasureandrecordthevoltageattheHV+,+17HV,and+5Vtestpoints.
9. Isolatecompressorpower.
10. WaitfortheLEDsontheBackplanetoturnoff.
11. RemovethePWMfromtheBackplane.RefertoSection4.28.4PWMRemovalandInstallationonpage
228.
12. Applypowertothecompressor.
13. MeasureandrecordthevoltageattheHV+,+17HV,and+5Vtestpoints.
14. Ifthevoltagesdonotchange,thePWMisnotthesource(ornottheonlysource)ofenergydrain.
4.28.3.2 Verify Functionality of the Five Output Channels
1. Verifythebearingcoilresistancesarewithinspecification.RefertoSection4.29.3BearingVerification
onpage230.
2. Verifythebearingsensorresistancesarewithinspecification.RefertoSection4.29.3Bearing
Verificationonpage230.
3. VerifythevoltagesattheHV+,+17HV,and+5VBackplanetestpointsarewithintheexpectedvoltage
rangesshowninTable4-42BackplaneTestPointValuesonpage215.
4. PerformabearingcalibrationusingtheSMT.
5. Watchthebearingforceswhilethecompressorisgoingthroughitscalibrationsteps.Thesoftware
shoulddisplaybothapositiveandnegativebearingamperageforeachbearingposition(FrontRadial
X,FrontRadialY,etc.).Ifyoudonotseebearingamperageatall,orinonlyonedirection(+/-),its
possiblethePWMisfaultyonthatchannelassumingthebearingcoilverifiedinStep1wasgood.

NOTE
IfoneofthePWMoutputchannelshasfailed,thecorrespondingbearingchannelreturnsagainof0whenabearingcalibrationis
performed.

6. Ifallbearingresistancesaregoodandoneormoreofthegainsis/are0,butnotallthegainsare0,the
PWMcouldbefaulty.
4.28.3.3 Verify Functionality of the Five Diode Sets
ToverifythediodesetswithinthePWMchannels,completethefollowingsteps:
1. IsolatecompressorpowerasdescribedinSection1.8ElectricalIsolationonpage22.
2. RemovetheServiceSideCover.RefertoSection4.1.3.1ServiceSideCoverRemovalandInstallationon
page54.
3. VerifytheLEDsontheBackplanehaveturnedoff.
4. Unplugthe250VDCinput(J4)fromtheBackplane.RefertoFigure4-238BackplaneConnectionson
page212.
M-SV-001-EN Rev. H-1/23/2023 Page 227 of 294