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Thread: Danfos Turbocor

  1. #1

    Confused Danfos Turbocor

    Does anyone know how to remedy the “Motor back EMF is low” fault on a Turbocor compressor?
    I understand that this fault may be because by reduced strength of the magnetic field in the rotor. Can the magnetic field strength be restored and if so how.

  2. #2
    Join Date
    Mar 2003
    if you clear it, does it come right back? or is this a one time fault. do you have monitoring software? do you have an air card? if you do, it might be best to contact DTC and have them dial in through your disputer with team viewer to help you.

  3. #3
    Join Date
    Aug 2009
    Ontario, Canada
    You need to look at your fault logs... If your Back EMF is below .09 when the compressor is above 20,000 RPM then you may be dealing with a partial demag of the shaft, Are you getting any other faults?

  4. #4
    The data below is typical from the fault log. The RPM is over 30000 and the back EMF is below 0.07. It certainly seems like deterioration of the magnetic strength.

    Compressor Demand% 83.20%
    Inlet Guide Vane% Open 44.70%
    Suction Pressure 208.4 kPag
    Discharge Pressure 923.7 kPag
    Suction Temperature 0.9 deg.C
    Discharge Temperature 47.6 deg.C
    Cavity Temperature 37.8 deg.C
    Controller PCB Temp 40 deg.C
    Back Plane Temp 29.8 deg.C
    Stepper PCB Temp -219.8 deg.C
    Entering Water Temp 9.6 deg.C
    Leaving Water Temp 7.1 deg.C
    Estimated Minimum Speed 32896 RPM
    Maximum Speed 37257 RPM
    Display Units Metric
    24VDC Supply Voltage 23.2 VDC
    Stepper#1 Control Mode Liquid Level 1
    Stepper Motor#1 %Open 22.30%
    Stepper#1 Process Variable 4.30%
    Stepper#1 Control Mode Load Balance
    Stepper Motor#2 %Open 0%
    Stepper#2 Process Variable 10.70%
    Motor Cooling Solenois Open 1
    Actual Shaft Speed (RPM) 36303 RPM
    Desired Shaft Speed (RPM) 37257 RPM
    Inverter Side Motor Amps-Id 12:00 a.m.
    Earth Leakage Current 0.1 A
    3Phase Power Input 53
    Inverter Temperature 45 deg.C
    Back EMF 0.06332
    Shaft Status Leviated
    Ax Un-balance % 0%
    Fr Un-balance % 0%
    Br Un-balance % 0%
    Ax Force Amps -0.32 Amps
    Fx Force Amps 0.42 Amps
    Fy Force Amps 0.18 Amps
    Bx Force Amps 0.2 Amps
    By Force Amps 0.29 Amps
    DC Bus Voltage 513Vdc
    3 Phase Amps 92 Amps_AC
    3 Phase Voltage 389 VAC
    SCR Temperature 24.9 deg.C
    Motor Fault Motor back EMF is low.
    Motor Alarm No Faults.
    Bearing Fault No Faults.
    Bearing Alarm No Faults.
    Compressor Alarm No Faults
    Compressor Fault BMC Fault.

  5. #5
    Join Date
    Aug 2009
    Ontario, Canada
    So if you are dealing with a partial demag of the shaft, To my knowledge the only we to have this happen is improper refrigerant cooling, You may want to check that out. What model of compressor?

  6. #6


    This one is a TT300. And yes the refrigerant flow has been checked, solenoids are working.

    Earlier it did have a couple of single phase over current faults due to flooding of the evaporator. The level sensor failed causing the flood. This was rectified and the compressor ran for only a couple of days before the low back EMF fault started to occur.

    If the rotor magnetic field has been weakened, can this be repaired or will I need to replace it?

    Is it possible to align the shaft in a static magnetic field while in statue for example?

  7. #7
    Join Date
    Aug 2009
    Ontario, Canada
    Nope it is now a very expensive center piece for your living room! Have you spoke with DTC tech support. You can send your fault logs to them and they will look over them

  8. #8
    Join Date
    Mar 2003
    Dont send logs to them, get them to dial in via team viewer and help you through your laptop. you will get better results. if you can, setup in advance. They can use access codes that you cannot and see more and do more remotely.

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