Electro Motor Testing Procedure

PT. BINTANG LESTARI PERSADA Electro Mechanical Workshop

ELECTRO MOTOR TESTING PROCEDURE AC LOW – MEDIUM VOLTAGE

1. Record name plate and perform visual inspection and reporting.1.1. Part listing (terminal, fan, pulley / coupling, thermostat, etc).1.2. Rotate shaft with hand (noise, jammed part, foreign object).1.3. Cooling device (damage, crack, leak)1.4. Complete condition

2. Perform Insulation Resistance test.2.1. The recommended insulation resistance to ground, R min, when measure at or corrected to

40° C is given by :

R min : n + 1, in Megohm. When n is the rated machine potential in kilovolt. A 500V Megohmmeter is suitable for testing of machine rated up to 2400V. above that voltage, a 1000V Megohmmeter is recommended. Test voltage should be applied for one minutes ( ref IEEE std. 43).

2.2. If test are pass, continue to step 32.3. If test are fail, follow this step :

2.3.1. Dismantling electro motor to perform complete inspection.2.3.2. Measuring Insulation resistance of Stator after rotor has been removed2.3.3. Perform inspection and documented for evidence of damage or degradation such as :

1. Puffiness, cracking, separation or discoloration as indication of thermal aging.2. Contamination of coil and connection surface.3. Abrasion or other mechanical stresses.4. Evidence of partial discharge (Corona).5. Loose wedge, filler, ties, banding, or surge rings.6. Fretting of supports, Bracing, or Crossings (an indication of looseness and

movement).( ref IEEE std. 432 sec. 5. )

2.3.4. Turn to Turn resistance or phase balance test (must equal, tolerance is ± 0,3 Ω).2.3.5. Surge test wave form

Using wave diagram as describe below to analyze winding condition.BAKER Surge Winding Analyzer ( ref BAKER Tech – Surge Test ).

2.3.6. Perform Interlaminar insulation test with growler test.2.3.7. Polarity and ball rotation test.2.3.8. Complete reporting of electrical condition

Doc. SOP TESTING Page 1 of 7 Low-Med Voltage AC Motor Rev. 1.1 - 2009By. Mirza Aminudin


3. Polarization Index (P-I) test.3.1. P-I test should be performed at the same voltage as the test in paragraph 2.1 for 10 minutes.

The recommended minimum value of polarization index for winding rated class B and higer is 2.0.

PI=10Minute Result1Minute Result

=≥2.0

( ref : IEEE std. 43 sec 9.2 )3.2. P-I test below 2.0 is acceptable if insulation resistance result is more than 5000 Megohm

( ref : IEEE Std. 43.2000. 12.2.2.2 )4. Surge Test – Winding analyzer.

Reference to paragraph 2.3.5. from the wave graphic we can determine is winding are in good condition. Perform full reporting with print out or photograph of the result.

5. Perform No-Load Test.5.1. Speed

No-load running test should be made at rated voltage and frequency. Measure and compare with nameplate speed.

5.2. CurrentNo-Load current should be compared with full load current.

5.3. Cooling systemThe cooling system must be verified as being operational

5.4. Sound levelTest may be made for sound level as an indication of fault or as an irritation to those in the machine ambient.( ref. NEMA stds. MG 1-12.53, 1-12.81, and 1-20.50 )



5.5. Bearing temperatureAmbient and bearing housing temperatures may be measured periodically until temperatures are stabilized.

5.6. Frame temperatureAmbient and Frame temperatures may be measured periodically until temperatures are stabilized.

5.7. Vibration testThe vibration test should be in accordance with NEMA std. MG 1-7 for standard machine, as arrange with customer, or as necessary to check the operating characteristics of the machine. When there are special requirements, NEMA std. MG 1-7 for special machine is recommended.The unfiltered vibrations limits for resiliently mounted on standard machine (having no special vibration requirement), and based on rotational speed, are shown in next table. Vibration levels for speed above 1200 rpm are based on peak velocity of 0.15 inch/s (3.8 mm/s). Vibration limit for speed below about 1200 rpm, are based on the peak-to-peak velocity equivalent of 0.0025 inch (0.0635 mm) peak-to-peak displacement. For machine with rigid mounting, multiply the limiting value by 0.8.To obtain approximate metric rms equivalent, multiply the peak vibration in in/s by 18. ( ref. NEMA std. MG 1-7.08.).5.7.1. If the test pass, continue to next step5.7.2. If the test fail, proceed to check from paragraph 2.3 then continue to paragraph 7

5.8. Performance testFull load test may be made as arrange with the customer or as necessary to check the operating characteristic of the machine.( ref. IEEE std. 112 and 115 and NEMA std. MG-1 )

6. Complete of testing6.1. Providing electrical and mechanical report to customer

To check and analyze result of testing or repair with customer, each report must be have detailed item name plate, workshop ref number, and specific test or repair have been perform. To give evidence that the specific repair are perform, must give photograph report.

6.2. Providing warranty letter to customer6.3. Packaging as appropriate handing of electro motor

7. Mechanical checkAfter dismantling motor unit that not pass electrical or testing we should verified the problems, with mechanical check we will find source of each failed criteria. 7.1. Shaft

Shaft should be check for wear, cracks, scoring and straightness.7.1.1.Shaft Extension

Shaft extension should be smooth, polished and concentric with the shaft diameter. Shaft extension diameter should be checked.

7.1.2.Diameter tolerance7.1.2.1. NEMA Frame machine



7.1.2.2. IEC frame machine

7.1.3.Permissible Run-Out7.1.3.1. NEMA Frame machine

7.1.3.2. IEC frame machine



7.1.4.Keyway width tolerance7.1.4.1. NEMA Keyway

7.1.4.2. IEC Keyway

7.2. Bearing7.2.1.Ball or Roller Bearing

Check when operated for temperature, noise and vibration condition. See reference to each bearing manufacture standard for acceptance clearance.

7.2.2.Sleeve BearingSleeve bearing should be uniform in diameter or proper fit in the housing, smooth internally, and suitably grooved for adequate distribution of lubricant.When sleeve bearing are remanufactured or replaced by new bearings, the diametral clearance should be set to original equipment manufacturers specification if available. Otherwise, the value in table below are provided as guide.



7.2.3.Sleeve bearing end thrustBearing of horizontal machine should be positioned on the shaft to eliminate end thrust against either bearing.

7.2.4.Oil RingOil ring should be true and rotate freely. Retainer, when provided, should be inspected or replaced if necessary.

7.2.5.SealsSeal clearance should be set to original equipment manufacturers specification if available. otherwise the value in table below provided as a guide, measure the final seal dimension.

7.3. Lubrication7.3.1.Grease

Grease passage and pipe should be clean, grease inlet should be equipped with fittings. Grease should be compatible with customer lubricant. In the absence of the machine manufacturers lubrication instruction, the grease reservoir should be filled with approximately 1/3 capacity

7.3.2.OilOil should be compatible with customer’s lubricant, there should be a means to determine oil level, such as oil sight gauge.

7.4. Frame and housing bearingFrame and housing bearing should be examine for defects. Cracks and breaks should be repaired and fits restored to manufacturers specification.Mounting surface tolerance, eccentricity and face run-out



7.5. LaminationThe rotor lamination should not be loose on the shaft, sleeve or spider on which the lamination stack is assembled. The fit should be restored if it is found to be loose. The outer diameter of the rotor laminations should be true and concentric with bearing journals.The stator lamination should not be loose in frame. The bore of stator laminations should be true and concentric with the rabbet (spigot) diameter of the frame.

7.6. UnbalanceDynamic balancing should be to the level specified by customer. In absence of requested level, dynamic balancing to balance quality grade G 2.5 (ISO 1940/1) should enable the machine to meet final vibration limits.Locate balance weights so they do not interfere with other components.

7.7. Rotor centerAssemble both of housing bearing into frame and measure bearing to bearing length, compare result with rotor bearing to bearing.


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Electro Motor Testing Procedure