4. Manufacturing Process of Stator Bar
• Conductor Cutting
• Transposition
• Mechanical Advantage
• Electrical Advantage
5. Manufacturing Process of Stator Bar
• Crossover Insulation
• Stack Consolidation
[70 𝑘𝑔/𝑐𝑚2
, 160˚-180˚ C,2 hours]
• I.S.T. (Inter-strand ShortTest)
6. Manufacturing Process of Stator Bar
• Forming and Marking
• [bars are bent]
• [marking is done for Lugs and extra conductor cutting]
• Extra Conductor Cutting
• [According to marking, extra conductor is cut]
• Lug Mounting
• [Contact Sleeves andWater box Bottom are mounted on marking]
7. Manufacturing Process of Stator Bar
• Brazing
• [Castromask Coating]
• [Main BrazingTemp. - 810˚C]
• [Water Box BrazingTemp - 670˚C]
• Nitrogen PressureTest
• [P > 11 kg/𝑐𝑚2]
• Pickling
• [Bars are dipped in Pickling Solution]
• [for 10 minutes and heated up to 50˚C - 70˚C]
S.N. Ingredient Quantity (Parts by weight(P.B.W.))
1 Water 100
2 SulphuricAcid 10
3 Phosphoric Acid 5
4 Hydrogen peroxide 5
8. Mechanical QualityTests
• WaterTest
• [1 kg/𝑐𝑚2Pressure]
• Thermal ShockTest
• [25 cycles of hot water(90˚C) and cold water(30˚C), (8 minutes each)]
• [To check strength of hollow conductor and loose brazing]
• Helium LeakageTest
• [13 kg/𝑐𝑚2
Pressure]
• [To check minor leakage in brazing]
• [Helium Leakage is detected by using Helium Mass Spectrometer]
9. Insulation
• InsulationTaping
• 1 Layer - CuTape Soldering (Manually)
• 1 Layer - ConductingTape (Manually)
• 1 Layer - Fine Mica Paper (Manually)
• 16 Layers (By CNC machine)
• 4 Layers – Fine Mica Paper
• 12 Layers – Mica Split
[called main Insulation]
10. Vacuum Pressure Impregnation
• Step 1 –Waiting
[Heated using Brine, BarTemp. 65˚C]
• Step 2 –Vacuum
[Pressure of 100 mbar is maintained
Using rough vacuum pumps]
[Fine vacuum Pump takes the pressure
at a very fine value of 0.1 mbar]
[This temp. is maintained for 10 hours ]
P riseTest:
[Stator Bars are left without any input
for 10 minutes]
[Pressure rise ≯ 0.6 mbar]
** Resin is started to be heated at last
3.5 hours of the 10 hours.
11. Vacuum Pressure Impregnation
• Step 3 – Filling
[Hot Resin is filled inside the tray from downwards using Pipes with controlled
Speed.]
[Resin from the tanks is drained to Impregnation tank from lower valves with the
help of Nitrogen Pressure.]
12. Vacuum Pressure Impregnation
• Step 4 – Pressure Super Imposition
[To fill the resin inside the 17 insulation layers]
[Nitrogen Pressure of 4 bar for 2 hours]
• Step 5 – Drainage
[Resin is drained to the resin tanks
maintaining Nitrogen pressure of 2 bars]
• Step 6 – Aeration
[All the vacuum and Nitrogen Pressure is
Released by opening valves.]
• After aeration, bars are taken out and pressed at a closed box fixture on
baking wagon.
• After extra resin is removed, bars are baked in an oven.
13. Electrical QualityTests
• ΔtanδTest
• [To check insulation capacitance]
• [LDIC measurement system]
Voltage applied : 0.2Vn to 1.4Vn in steps of 0.2Vn.
The difference of two adjacent measurements should not exceed 1 × 10−3.
(WhereVn is the rated voltage of the generator)
Vn = 21kV for 600MWTG.
0.2 × 𝑉𝑛 = 0.2 × 21𝑘 = 4.2𝑘𝑉
Let reading in LDIC measurement system is = x = (Tan δ)1
0.4 × 𝑉𝑛 = 0.4 × 21𝑘 = 8.4𝑘𝑉
Let reading in LDIC measurement system is = y = (Tan δ)2
In the two continuous readings the difference x – y = ∆Tan δ < 1 × 10−3
14. Electrical QualityTests
• HighVoltageTest
[Duration 1 minute]
Voltage to be applied in HV test is calculated by following formula:
𝑉 = 2𝑉𝑛 + 1 1.5
Where,
V =Applied overvoltage
Vn = Rated voltage of Generator
ForVn = 21kV
𝑉 = 2 × 21𝑘 + 1 1.5
𝑉 = 64.5𝑘𝑉
16. TG Stator TG Rotor DC Generator atTG test bed
S.R.G.M. Naval Gun and Dummy Rounds
for testing at Defense Block
At Loco Shop SteamTurbine
Experience at B.H.E.L., Haridwar
