Traction Motor Failures - PART 1

    Large scale Traction Motor failures in recent months reflect major short comings in existing maintenance practices followed by sheds. 39 TM line failure cases have been reported so far.

Item	Apr/09 to Dec/09
	Total	M	N	S
TM air duct	1		1
TM arc ring, cable terminal ,Teflon band	6		3	3
TM armature	5	3	2
TM bar cut	1			1
TM Bearing	7	2	1	4
TM carbon brush, holder spring	9	2	7
TM interpole, insulation	6	3	3
TM pinion	1		1
TM speed sensor	3			3

Sheds must implement following maintenance practices in addition to existing practices followed.

·  OVH and testing of TM should be done as per format enclosed.  Additional practices to be included by sheds should be suggested so that uniform maintenance pattern can be followed in NF railways.

·  All TMs requiring rewinding, IR attention, and magnet frame attention should be sent to DMW.

·  Sheds should chalk out action plan in order to give focussed need based attention.

·  Daily one hour training for maintenance staff so that every sectional staff is well conversant with overhauling and additional maintenance procedure.

·  Exception statement should be made for TMs running with low IR and high MV drop.

             

Action to be taken during trip maintenance:

Thoroughly clean TM with dry air and wipe with slightly moist cloth dipped in        Orion 77.

1.     Measure manomatric pressure during every trip.   It should not be less than 90cm in WDM_{2 and} 100 CM in WDG₃ / WDM_3.

2.     Measure TM temperature during incoming stage. TM temperature variation beyond 6⁰C in loco to be investigated.

3.     Check sign for flashover, sparking, high carbon deposit etc. on armature.

Measure IR during every quarterly schedule.  No fall in value from previous reading   should be permitted.

4.     Check condition of end fittings, loose bolt, burnt grease during every trip.

5.     check arc ring condition for sign of flashover, missing bolts, loose bolts etc

6.     Premature wear of carbon brush or repeated breakage of carbon brush is sign of major 

7.     During M4 and above Sch. loosening of Insulator Stud to be checked. Holder with      loose stud to be changed in-situ.

8.     TM should be taken out and examined in case of any logging of fault code for TM high Temperature.

TM Carbon brush pigtail breakage:

1.               Check pigtail pull out pressure by spring balance.

2.               Apply adhesive over pigtail root.

3.               Use nylon tag to secure pigtail. This will eliminate failure even if pigtails accidentally  

            come out.

4.               Carbon brush to be changed in set only.

5.               If only one carbon brush is showing sign of wear / damage, then thoroughly investigate the cause of wear of the carbon brush & only after rectification of actual cause carbon brush should be changed.

Action to be taken during overhauling of TM :

Shed should add these maintenances instructions in their overhauling practices.

S N	Assy/ Sub assly	Cause  of failure	Suggested Action plan
1.	TM Magnet frame	FIELD IR ZERO	1.    Field IR to be checked after baking in oven for 08 hrs. 2.    Final IR to be checked after watching it 03 days.  It should remain at 500MΩ     or above. 3.    Training to be given to staff to check IR after 3 days watching.
		IP IR = 0	1.    0.38 MM Nomex paper packing should be provided around all four-pole shoes. 2.    Back side of all pole shoes are to be insulated with 0.76m.m.  Nomex paper. 3.    Pole shoe having sharp edge to be removed. 4.    Training to be given to staff to replace old mica insulation and to fit standard size Nomex paper. 5.   IR value to be checked correctly by Million Mega Ohm  eter, which would clearly shown the correct IR value of IP with higher accuracy, by which  IR to be monitored Easily.
2.	TM ARM	ARMATURE IR ZERO	1.    Armature IR should be checked after air blowing and 2 hrs. Oven heating.  It should be 500 MΩ or above.   After cleaning vertically by Orion 77 it being baked in oven for 8 hrs.  Final IR to be checked after watching it 3 days.  It should remain at 500 MΩ or above. 2.    Armature cooling hole to be blown by air through a long perforated copper pipe, to ensure proper cleaning inside the armature.. 3.    Training to be given to staff to check IR after watching.3 days 4.     IR value to be checked correctly by Million Mega Ohm Meter, which would clearly show the correct IR value of Armature  with higher accuracy. 5.    Brazing to be done by Brazing Transformer only, uniform heating of Brazing surface can be achieved by Brazing Transformer only, Brazing by oxy-acetylene gas is to be avoided to prevent failure. 6.    A Surge comparison Tester is to be procured, on available of this m/c inter turn short cut test is to be done extensively. 7.    MV drop is to be checked cautiously during sch examination. 8.    During OVH of TM Armature, UST of Arm Shaft must be done. 9.    Armature Shaft In-Situ UST of TM Armature to be done during yearly sch. at  the time of Truck OVH. 10.  Under cut the commutator segments. It should be 0.030’ to 0.049’ (1.25 mm). Mica thickness shall be1.5mm.Chamfer the commutator segment with tools having the angle of 60 degree. Polish the commutator surface with silicon paper.
3.	TM BRG.	P/E BRG. SEIZED	1.    Radial clearance of bearing to be checked before fitment and after fitment. 2.    During no load test temp rise of both side bearing to be kept below P/E-9 degree & C/E-16’C strictly. 3.    Dominant frequency to be  measured on vibration test bed 4.    Use SPM and engineer’s stethoscope. 5.    Do not refit old inner race. 6.    No Load Test should be done on a Test Stand isolated from Earth Crust Vibration. 7.    Vibration velocity, acceleration and displacement to be measured in 03 axes e.g. vertical. Horizontal and axial direction. 8.    Shock Pulses to be measured in terms of L.R. (Low rate of occurrence of high shock value) and H.R. (High rate of occurrence of low shock value) representing Bearing condition and Lube condition respectively. 9.    RC & OBC measurement is to be done .i)R. C. Bore Dia, ii) maximum and minimum value of Front and Rear Radial and Diametric to be done. iii) O.B.C and R.C. slot width to be checked. iv) O.B.C. inside Bore dia is to be measured.
		C/E BRG. SEIZED
4.	TM Pinion	PINION TEETH Broken	1.     Pinion having life more than 15 yrs to be weeded out from service. 2.    Pinion having profile deviation more than 15 thou to be rejected . 3.    100% Zyglow test to be done before fitment. 4.    D.P. test of Pinion during yearly sch. To be done. 5.    Pinion advance to be ensured.
5.	TM Arc. Ring Loose	ARC  RING Mounting Bolt Loose	1.    100% arcing mounting bolts are to be replaced by M12 x 40mm long bolt. And both side of Arc ring to be welded properly in End shield. 2.    Defective Arc Ring having damaged thread and heavy flash mark are to be changed by new one.
6.	TM Brush Holder	INSULATOR STUD,spring Broken	1.    Single Unit Epoxy type Brush Holder to be procured from reliable source and ARCO make brush holder to be replaced. 2.    During M4 and above Sch. loosening of Insulator Stud to be checked. Holder with loose stud to be changed in-situ. 3.    All DMW/Motor holder connections to be checked and half thread length bolts are to be replaced. 4.    DMW/PTA  to be informed, not to use half thread. 5.    Holder Lead connection to be checked properly for any crack before fitment. 6.    Socket connection hole is to be checked for oversize. 7.    Spring Tension of all holder pocket must be checked and to be maintained at the value of 4.5 kg to 5.5 kg. 8.    During OVH of Holder Pocket must be checked for any crack or defects.
		Cables and terminals	1.    Visually examine cables and cables to replaced in case of defective ,perished insulation 2.    Provide sleeve over cables for protection against damage. 3.    Check condition of cables under cleat joint and provide rubber cushioning. 4.    Securing of cables to prevent damage on run by rubbing. 5.    Measure MV drop of terminal, replace terminals in case of high MV drop.
7.	TM Carbon Brush		New carbon brushes received from store to be modified by using araldite on pigtail groove and pigtail strings to be tied up together by plastic make Cable Tie.