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Home / Technical Articles / Testing and commissioning procedure for electric motors

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

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

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Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.

25 Comments


  1. Ali Akbar Ahmadi
    Sep 10, 2020

    Hi
    It was very useful for me.


  2. Mohammad Farag
    May 21, 2019

    Please mention the the link of the Reference that you mentioned above for Form 14 – Inspection of electric motor – Cage-induction type (incl. control unit):

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


  3. kishor kajrolkar
    Feb 08, 2019

    Dear Sir,
    We have planned to design a dual compressor 600 tonne Air conditioning plant. Each motor rating is 280 KW& Medium Voltage ( 6.6 KV). The motor is refrigerant cool.Please let me know site and factory commissioning tests as per the Indian Standard.

    Thanks

    Kishor kajrolkar


  4. A.Jokar
    Jan 18, 2019

    Hello
    I ordered a 11-kW three-phase electromotor to make.
    What level of inspection do I have during construction?
    Which one of the factory tests is better to attend?


    • T S GUPTA
      Jun 27, 2019

      During factory acceptance test (FAT) min below to be witnessed –
      1) No load & Full load current.
      2) Max. current/ Thermal withstand limit of winding insulation.
      3) Vibration (peak & RMS)

      Level of Inspection during construction (SAT)-
      1) Insulation resistance (IR) to be checked and shall be 100 Mega Ohm (MΩ) with 1000 V Megger.
      2) Winding resistance shall be maximum of 2 Ω
      3) Vibration 2 mm/s RMS and 5 mm/s Peak.


  5. J A i m e Jaime Miguel
    Nov 12, 2018

    The information for testing and commissioning of motor was informative very useful.

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