Testing and Commissioning Procedure For Motors

Testing and Commissioning Procedure For Motors // Photo by TECO Middle East (TME)

Scope Of Motor Testing

It should be noted that the scope of motor testing depends upon the motor type and size, this being indicated on the inspection forms.

Motor vibration shall be measured in a tri-axial direction, i.e.:

  • Point x axis – side of bearing housing at shaft height
  • Point y axis – top of bearing housing
  • Point z axis – axial of bearing housing at shaft height
The measurements shall be carried out with an instrument conforming to ISO 2954 (10-1000 Hz frequency range). With the motor at normal operating temperature, the vibration velocity shall not exceed 2.8 mm/s RMS, or 4 mm/s PEAK, in any direction.

For bearings fitted with proximity probes, the unfiltered peak-to-peak value of vibration (including shaft ‘run-out) at any load between no load and full load, shall not exceed the following values:

  • 50 µm for two-pole motors
  • 60 µm for four-pole motors
  • 75 µm for six-pole or higher motors
Motor bearing

Motor bearing (photo by CCLW INTERNATIONAL)


Bearing temperature rise limits following a ‘heat run’ of 3.5 – 4 hours are as follows:

Rolling bearings:

  • Outer ring measurement max. 90 °C
  • Temperature rise from ambient max. 50 °C

Sleeve bearings:

  • Oil temperature max. 90 °C
  • Bearing temperature rise by RTD max. 50 °C
  • Lub. oil temperature rise from ambient max. 30 °C (for forced lub. oil systems).
When commissioning or re-commissioning motors, precautions shall be taken to avoid excessive vibration caused by the phenomenon known as ‘soft foot‘; i.e. feet which do not have solid flat contact with the base prior to the tightening of the holding-down bolts.

This may be measured and rectified during installation or detected during running by the loosening of each holding-down bolt in turn while measuring motor vibration.


Motor ‘Soft Foot’ Condition

‘Soft feet’ are those which do not have solid flat contact with the base prior to the tightening of the holding-down bolts; one or more feet may be ‘soft’ as shown in Figures 1 to 3.

The profile of the foot contact area may be as shown in Figures 4 to 6.

The profile of the foot contact area

The profile of the foot contact area (Figures 1, 2 and 3)


  • Figure 1 - Machine resting on 3 feet, foot 4 is raised or ‘soft’
  • Figure 2 - Machine resting on diagonal formed by feet 3 and 4, feet 1 and 4 are ‘soft’
  • Figure 3 - Bottoms of all 4 feet are not parallel with base, feet 3 and 4 are ‘soft’
Profile of 'soft foot' contact area

Profile of 'soft foot' contact area


NOTE: Re-machining of rotor feet is required in Figures 4 and 5; temporary use of wedge-shaped shims may be acceptable (maintenance).

Forms

Form 14 – Inspection of electric motor – Cage-induction type (incl. control unit)

Inspection of electric motor cage-induction type (including control unit)

Inspection of electric motor cage-induction type (including control unit)

Form 4 – Inspection of Switching Units – HV Switchgear

Inspection of Switching Units - HV Switchgear

Inspection of Switching Units - HV Switchgear

Form 11 – Inspection Of Outgoing Unit – LV Switchboard

Inspection Of Outgoing Unit - LV Switchboard

Inspection Of Outgoing Unit - LV Switchboard


Reference: Field Commissioning and Maintenance Of Electrical Installations and Equipment Manual


About Author //

author-pic

Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears. Professional in AutoCAD programming and web-design. Present on



9 Comments


  1. RATI KANTA
    Nov 25, 2014

    What are the different conditions for measuring the vibrations of a synchronous motor.


  2. Fadli
    Jan 29, 2014

    Hi Edvard. Is this extracts from Shell DEP? I have seen the forms and some sketches from such documents.


  3. engmido
    Nov 14, 2013

    please

    could you tell me about turbo generator testing & commissioning procedure ??


  4. mohammed
    Oct 20, 2013

    Good Article. Can some one suggest the basic test to be carried out on induction motor if a motor is unservice,acceptableresistance value etc……


  5. kramin
    Oct 02, 2013

    thanks for good article,, useful for commissioning and maintenance staff


  6. adipriya
    Sep 20, 2013

    Hi Edvard kindly some info related to verticalmotors


  7. adipriya
    Sep 20, 2013

    The problems facing in our Plant with LT motors
    1.When we open motor for overhauling we find a lot of grease inside it even though nipples are provided for grease in and out,The frequency of greasing is also right.What may be the reason?
    2.In vibration report mostly they say high frequency components in bearings and recommend us to grease.Is this a right procedure?
    3.If we check resistance and inductance before rewinding and if we check after some months and if we find a variation in Resistance and Inductance what may be the reason?(Resistance we can say short or open in turns)
    4.Why double grounding is needed for motors?(Is it just to maintain availability of one earthing even if other disconnects due to some problem)
    5.If any information to vertical motors like vibration,IS standards please post


    • Sadha
      Sep 21, 2013

      Hi Adipriya,

      Please find some of the answers for your question.
      1.When we open motor for overhauling we find a lot of grease inside it even though nipples are provided for grease in and out,The frequency of greasing is also right.What may be the reason?
      It is basically the grease got lost its viscosity. It happens due to long running hours, over heat, may be high ambient, Etc.
      3.If we check resistance and inductance before rewinding and if we check after some months and if we find a variation in Resistance and Inductance what may be the reason?(Resistance we can say short or open in turns) – Resistance value may increase becuase of its life. Littel variation in resistance and inductance doesn’t mater. You will see a big variation when you have a short inside.
      4.Why double grounding is needed for motors?(Is it just to maintain availability of one earthing even if other disconnects due to some problem)
      5.If any information to vertical motors like vibration,IS standards – Yes, you are right. It is for redundancy. nothing else. I think some standards (IS, IEC) requires doube earthing for safety.


      • adipriya
        Sep 21, 2013

        Thank u sadha

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