1. Coach alternator

2. Alternator Ratings in use (at dc output terminals)
3 kW for MG TL coaches
4.5 kW, 120 V, 38 A for TL coaches 12 kW, for MG AC coaches and Jan shatabdi
18 kW, 130 V, 140 A for under slung AC coaches
22.75 kW (optimised) for RMPU coaches
25 kW, 130 V,193 A for RMPU coaches
How capacity decided?

3. Governing specifications
Specification no
Equipment
RDSO/PE/SPEC/AC/ Rev 0 Amdt 1
3 & 4.5 kW, 110 V brushless alternator with RRU
RDSO/PE/SPEC/AC/ Rev 0 Amdt 1
18 kW alternator
25 kW alternator with RRU
RDSO/PE/SPEC/AC/0015 Rev 0 ,amdt 1&2
ERRU for 4.5/18/25 kW alternators

4. Governing specifications/Drgs
Specification/Drg no
Equipment
RDSO drg SKEL 4024 alt 1
Mounting arrgt and drive
RDSO drg SKEL 3645 alt 1
Alternator V grooved pulley
RDSO drg SKEL 3652 alt 2
Axle V grooved pulley
RDSO/ELPS/SPEC/TL/13
Alternator and Axle pulley
Rubber pad for Axle pulley
RDSO/PE/SPEC/AC/
V Belt
RDSO drg SKEL 3940
Spring tensioning device
RDSO/PE/AC/SK/
25 kW alternator outline

5. Governing specifications/Drgs
Specification/Drg no
Equipment
RDSO drg SKEL 3943 alt 4
Suspension hanger pin
RDSO drg SKEL 4022 alt 3
Safety chain for 18/25 kW
RDSO/PE/SK/AC/
Terminal board for 4.5/25 kW

6. Alternator
Quantity
TL coaches 1 set/coach
All AC coaches except FAC 2 sets/coach
FAC 1 set/coach (being increased to 2/coach)
Used for charging battery set of 56 cells of 800/1100 LA at nominal 110 V and catering AC and TL load of the coach
RRU/ERRU used for
Rectify ac output of alternator
Regulate output of alternator
Prevent reverse flow of current from battery

7. Alternator: Approved vendors
Part I
Part II
4.5 kW
KEL Kundra
Unilec
SIL
PD Steel
HMTD Taloja
Kapsons
Presstech
Best & Crompton
Stesalit
IC Electrical
25 kW
KEL Kundra & Kasargod
IC Electrical*
* Not for RRU

8. MOUNTING ARRANGEMENT

9. Alternator: General technical data
Hetro polar, inductor and self exciting type having NO windings on rotor
Suitable for bi-directional generation
Operating condition -5 to 55 0C and 100% RH
Bogie transom mounted
Universal applicability
Able to operate without battery
Rotor shaft made of EN 24 (hardened and tempered)
Coach wheel Dia: New/fully worn -915/813 mm
Rotor and Alternator pulleys dynamically balanced
Finished shafts to be 100% ultra sonic tested
I/P & O/P sockets terminated on separate terminal posts

10. Alternator: General technical data
RRU is magnetic amplifier type field excitation control.
Insulated cleat provided on frame to support cables
Dual coated enameled winding wires and VPI adopted
Winding star connected (formed in stator overhung)
RRU has un-controlled, 3 phase full wave rectifier
RRU regulate O/P voltage at all speeds RPM and at all loads from 10 A-Irated
Universal RRU when used with other make Alternator MFO permitted tolerance of RPM
Sr no of Alternator: Ist two digits-Yr of mfr, Next two digits- month of mfr & No of m/c manufactured in month

11. Alternator: Scope of supply
Each alternator set comprises of
1 TL/AC alternator with 1/2 V grooved pulleys
Safety chains 2(TL)/3 25 kW
1 RRU/ERRU
Belt tensioning device complete
Axle pulley complete with rubber pad and hardware
Suspension pin complete with hardware
Crimping type sockets for Alternator and RRU/ERRU
Maintenance manual
Items procured separately
V belts 4 (TL), 6+6 (AC)
Nylon suspension bushes 2/set

12. Alternator terminology
Cut-in speed: Alternator speed in RPM at which rectified output is 110 V at no load.
Min speed for full output (MFO): Min Alternator speed in RPM at which it gives rated O/P I at rated V.
Voltage and Current detector: Device to limit voltage and current of alternator to pre-set values.

13. Voltage vs Current characteristic

14. Alternator suspension Bracket

15. Coach Alternators
TL alternator
AC coach alternator

17. 25 kW alternator outline

19. Modified Nylon bush arrangement issued vide RDSO letter no EL/1. 6. 9
Modified Nylon bush arrangement issued vide RDSO letter no EL/ Dt

20. Self Generating System- Alternator

21. Self Generating System- Alternator
Principle of working
Both windings (AC & Field) accommodated in Stator
AC windings distributed in small slots
Field winding concentrated in two slots and each coil spans half the total no of slots.
Rotor consists of stacked stampings like cogged wheel having teeth and slots uniformly distributed on surface skewing rotor axis.
Core of stator (completely embraced by field coils) retain residual magnetism, if excited once by battery.
Flux produced by field coils find its path through rotor
On rotation, rotor offers varying reluctance path for the field flux.
Varying field flux induce alternating voltage in AC coils
Frequency depend on speed and magnitude on speed and level of excitation

23. 25 kW Alternator Suspension pin

24. Self Generating System- RRU
Circuit diagram

25. Self Generating System- RRU
Functions
Rectification of 3 phase AC output of Alternator using full wave rectifier bridge
Regulation of voltage at set value
Regulating output current at set value
Components
3 ph full wave rectifier (Diode D1 to D6) with heat sinks
1 ph full wave rectifier (Diode D16 & D17) on heat sink along with free wheeling diode D18
Sensing diodes (D19 & D20) for current/voltage setting with zener diode Z1

26. Full wave rectifier

27. Alternator-Bearings 4.5 kW 25 kW L 10 life 16 million km at 1500 RPM
Drive end: NU-311 (cylindrical)
Non drive end: 6309
(Deep groove ball)
25 kW
Terminal end NU-312 (cylindrical)
Other end (angular contact ball)
L 10 life 16 million km at 1500 RPM
Make : SKF/FAG
NU-311
6309

28. Alternators- Salient features
4.5 kW
25 kW
Rating
120 V, 37.5 Amp
130 V, 193 Amp
Factory set at (1500 RPM)
128.5V at 1/2 load
128 V at 1/2 load
Efficiency
70% at full load and 1800 RPM
80 % at full load and 1800 RPM
Min RPM for 2 V ac rms
300 NM
Field wdg resistance
4.5+/- 0.5 Ω
8.5+/-1.5 Ω
Stator wdg resistance (phase to phase)
0.4+/ Ω
0.045+/-0.01 Ω
Suspension pin dia
/-0.10 mm
/-0.3 mm
Insulation class F H

29. Alternators- Salient features
Ripple content (max) 5% 3%
Alt pulley width
110.5+/-1.5 mm
200+/- 1 mm
Axle pulley width
210+/- 1 mm
Cut in speed (min)*
357 RPM
400 RPM
MFO (max)*
600 RPM
800 RPM
Alt pulley groove angle
34+/-0.5 0
36+/-0.5 0
Axle pulley groove angle
38+/-0.5 0
38 +/
Tensioning device working length
310 mm
295 mm
Distance of axle pulley from wheel hub mm
228+/-0.5 mm
Weight (max) NM
< 525 kg
* With new wheel dia (915 mm)

30. Alternators- Salient features
Current limit set between
228 & 232 A
Voltage not to dip <120 V at
225 A
Mating of Alt pulley with shaft
> 80 %
Free hanging clearance from RL
178 mm
O/P V tolerance (10 A to full load)
+- 4%
I limiting by potentiometer A
Voltage not to dip below 120 V at
Max Vset through potentiometer
140 V at 800 rpm on 10 A load
Max Iset through potentiometer
232 A
Bearing L10 life
> 16 million km at 1500 RPM

31. Alternators- Salient features
Bearing re-greasing interval
>30 M or 6 lac km
OVR set at V
Size of rotor (D * L)
No of teeth (slot) on rotor 8 12

33. Alternator capacity Assumptions
Cl 3 of UIC 550 OR stipulates : battery to supply full coach load for 3 hrs and lighting load for 5 hrs.
Assumptions
Conversion factors of 0.72 & 0.83 for 3 & 5 hrs discharge (cl 5.5 & 5.6 of IS 6848)
Condemning capacity of battery-80%
100% roof load (excldg NL) from 6-10 PM
50% Rdg lights from PM
20% light load (incldg NL) from 10 PM-4 AM
50 % roof light load from 4-6 AM
100 % fan load for 24 hrs
Ah efficiency of battery-80%
Avg Alternator current -90% 0f capacity
Battery capacity (10 hr)=Total load *3/0.72*0.8=5.2*TL
OR Lighting load*5/0.83*0.8=7.54*lighting load
Alternator capacity
To ensure that battery get fully charged in a night run of 12 hrs with generation to non generation ratio of 2

34. Alternator capacity Alternator capacity Avg load-A
Generation to non generation ratio-2
Non generation period –n hrs
Generation period -2n hrs
Load Ah by direct generation=A*2n
Load Ah through battery=A*n
Battery input=A*n/0.8=1.3*A*n
Total generation required- (2+1.3)*A*n=3.3 *A*n
In case of externally regulated=3.3*A*n/(2*n*0.8)
= 2.06*A
Back

35. Dyna drive for testing Generation /Load sharing of Alternators

36. Alternator RDSO SMI/MS’s
S no
SMI/MS N0
Description
Reference 1
AC/SMI/9
Instruction for re-assembly of NH type bearing of 18 kW KEL make alternator during POH
EL/7.1.21/K Dt 2
RDSO/PE/SMI/AC/ALT/ (Rev.0)
Fits and limits on bearings of alternators and motors used on AC coaches.
EL/7.1.38/1 Dt 3
RDSO/PE/SMI/AC/ALT/0003, 98(Rev.0)
Procedure for measuring bearing clearance of a free bearing. 4
RDSO/PE/SMI/AC/ALT/0004 –98(Rev.0)
Condition monitoring of bearings.
EL/7.1.38/1 Dt

37. Alternator RDSO SMI/MS’s
S no
SMI/MS N0
Description
Reference 5 
RDSO/PE/SMI/AC/ALT/0005–98(Rev.0)
Fitment of outer race of bearings in the housing.
EL/7.1.38/1 Dt 6
RDSO/PE/SMI/AC/ALT/0006– 98(Rev.0)
Testing and checking of new bearings for alternators and motors of AC coaches.
EL/7.1.38/1 Dt 7
RDSO/PE/SMI/AC/ALT/0007–98(Rev.0)
Guidelines to identify genuine and spurious/reconditioned bearings. 8
RDSO/PE/SMI /TL/ / (REV.`0’)
Proper mounting ,maintenance and handling of power and field diodes provided in RRU
April 1999

38. Alternator RDSO SMI/MS’s
S no
SMI/MS N0
Description
Reference 9
RDSO/PE/SMI/AC/0018–99 (Rev.0)
Proper load sharing in AC coaches.
EL/7.1.38/ 10
RDSO/PE/SMI/AC/0019 –2002 (Rev. '0')
Testing procedure for proper working of OV protection provided in 25 kW alternator.
EL/7.1.38/1 11
RDSO/PE/SMI/TL/ (REV.`0’)
SMI for checking shaft of TL alternator
Oct. 2003 12
RDSO/PE/SMI/AC/ (Rev. 0)
Protection of Lead wire of TL & AC Alternator
EL/ dt

39. Alternator RDSO SMI/MS’s
S no
SMI/MS N0
Description
Reference 13
RDSO/PE/SMI/TL/ (Rev-0)
For 4.5/25 kW RRU/ERRU voltage setting on TL and AC Coaches
June-2012 14
RDSO/PE/SPEC/TL/ (Rev-0)
Guideline to use standby circuit in ERRU
Aug-2012 15
RDSO/PE/MS/TL/ (Rev. '0')
Provision of modified terminal box cover for 4.5 kW 110 V TL Alternator
EL/ 16
RDSO/PE/MS/TL/ (Rev. '1')
Provision of OV protection in RRU of alternator used in SG AC coaches.

40. Alternator RDSO SMI/MS’s
S no
SMI/MS N0
Description
Reference 17
RDSO/PE/MS/TL/ (Rev. '0')
Provision of modified terminal board assembly in 4.5/18/25 kW alternators.
EL/ 18
RDSO/PE/MS/TL/ (Rev. '0')
Provision of filter circuit in RRU of 4.5 kW alternators used in TL coaches. 19
RDSO/AC/MS/22
Modification to cable layout from 18 kW alternator terminals to junction box of AC coaches.
EL/7.1.21/K dt 20
RDSO/AC/MS/24
Procedure for brazing winding wire with flexible lead wire on alternators.
EL/7.1.21/K

41. Alternator RDSO SMI/MS’s
S no
SMI/MS N0
Description
Reference 21
RDSO/PE/MS/TL/ 0002 – 99 (REV.0)
Arrangement for anchoring of outgoing cables from alternator TB/box to RRU TB and UF TB of TL alternators
EL/ dt 22
RDSO/PE/G/ (Rev. 0)
Guideline for rewinding of TL/AC Alternator
EL/7.1.38/1
Aug. 2005 23
RDSO/PE/MS/AC/ (Rev. 0)
For protection of lead wire in 4.5 /25 kW Alternator

42. Alternator Tests Test P T R A
Dimensional verification of all assemblies Y
Measurement of stator and field resistance
Temp rise test on Alternator and RRU N
IR test of Alternator and RRU
HV test
OC test
Load test
Current limiting characteristic test
Mechanical over speed and induced voltage test
SC characteristic test
Surge protection test

43. Alternator Tests Test P T R A Efficiency test Y N Environmental test
Hose proof test
OVP test
Special tests
Parallel operation of Alternators
Checking dynamic balancing of rotor and pulley
Temp rise test at 2500 RPM

44. Alternator tests Measurement of winding resistances: Temp rise test:
By suitable resistance measuring device at ambient temp. R20 averaged for 5 m/cs. Not to vary by more than +-7% of declared value.
Temp rise test:
Alternator run at Irated and 2500 rpm and repeated at MFO. Forced air-cooling 6 & 4 m/sec for alternator and RRU respectively. Temp rise by resistance method above ambient of 550 not to exceed 1150& ---- for AC & TL alternator respectively. Locations temp measured by point contact pyrometers. After test overload test at 222/--- A for 1 hr at MFO and 2500 rpm done

45. Alternator tests IR test
Measured before and after HV test between all terminals shorted together and body with 500 V dc megger. Value to be > 20 Mῼ.
HV test
Immediately after temp rise test 1500 ac rms 50 hz (gradually increased from 500 V) applied all shorted external terminals and frame for 1 min. For acceptance duration 5 sec and without temp rise test. ILeakage < 30 mA
Open circuit test
Alternator run at min 5 speeds 9500,900,1500,1800,2500) with field separately excited. O/P voltage vs field excitation curves plotted

46. Alternator tests
Load test : Conducted with resistance load and or with battery. All characteristic tests done at 129 V, 96.5 A at 1500 rpm. Test consists of , No load test, speed vs O/P and Current vs V test.
No load test: Conducted at base load of 10 A. DC O/P voltage recorded at MFO,1500,1800 and 2500 rpm and variation not to exceed 4% of pre set voltage.
Speed vs O/P voltage: Done at full rated and half rated current at speeds from MFO to max speed. V not to vary >+-4% of pre set value.
Current vs voltage: Done at 1800 rpm. I varied from 10 to 193 a keeping speed constant. V not to vary > +-4%.

47. Alternator tests
Current limiting characteristic test: Done after I vs V test. Point when , current doesn't increase even with load increase. Not to exceed 230 A.
Mechanical over speed and induced voltage test: Done just after temp rise or load test. Alt run for 2 mts in each direction with OC stator wdg anf separate excitation at cut-in speed level at speed of 3035 rpm.
Short circuit test: Done on cold m/c. O/P terminals short circuited with an Ammeter and excitation adjusted to achieve 25, 50, 75 and 100% full load. Curves plotted for various speeds.
Parallel operation: Done at 800,1800 and 2500 at 25,50 and 100% load. Difference not to exceed 30 A.

48. Alternator tests OV protection: Time delay of 3 s. Set at 145+-1 V.
Surge protection test: At 1800 rpm, full thrown off and O/P voltage rise recorded. Again full load leaving 10 A resistive load thrown off and V not to rise > 400 V and should drop to normal in 5 S.
Efficiency test : Efficiency at 1800 rpm to be >80%. Speed vs efficiency curves at rated load.
Environmental tests: Done on RRU only. Temp rise (dry and damp heat), in corrosive atmosphere, combined dust humidity and heat and vibration and shock test.
Hose proof test: for RRU, IP 55S of IS

49. Alternator tests Special tests Fire retardant test for terminal board
Ripple content not to exceed 3%. (Vmax-Vmin)/(Vmax-Vmin)*100 %
Mating of pulley with shaft: Done using plug and ring gauges and prussian blue and media
Shorting of power diode: At 1800 rpm and full load for 2”.
OC power diode
Junction temp of semi conductors
Dynamic balancing of rotor and pulleys
MFO at cold and hot condition
MHO measurement
Fire retardant test for terminal board