Rewinding of 3.3kV, 235kW, 1485 rpm vertical motor at FACT Udyogamandal

Stator rewinding and rotor balancing(3.3 kV): The scope of includes the following: 1. Removing cooling fan cover and fan, dismantling the motor, threading out the rotor from the stator core pack, inspection of stator /end covers/ bearing cups and other parts, debrazing of end connections and removal of old stator copper windings,removing heater, cleaning the stator slots. 2. Conducting stator core flux test(hotspot test). The reports shall be submitted to FACT engineer. If any issues are found after core flux test and it is found that the stator core need restaggering, the work shall be executed as per the schecule 2 . 3. If no issues found during core flux test, the rewinding of the stator core shall be done using class ‘F’ enameled double fiber glass covered electrolytic grade new copper conductors for rewinding coils as per the original shape and dimension by using special jigs and dies, insulating the slot portions using semi catherm insulating materials, moulding the slot portion in hydraulic hot press, applying flexible insulation to the overhang portion, inserting the coils in to the slots, banding the overhang portions in the surge ring, bracing, tinning, soldering, forming the end connection, preheating, conducting vacuum pressure impregnation(VPI), curing, fixing heater coils and heater covers, wiring heater coils to the terminal block, applying finishing varnishes. Good quality, glass laminated (or superior) wedges shall be placed over the coils in slots. Suitable spacer (filler material) shall be inserted between coils at the overhang portion, to avoid vibration of individual coils. 4. Rotor balancing with cooling fan and coupling half and doing dynamic balancing of rotor to balance quality grade of G2.5 at rated RPM. 5. Replacing the drive end and non drive end bearings of the motor. The contractor has to replace the drive end of motor with single-row cylindrical roller bearing NU 321 C3 bearings and non drive end with single-row angular contact ball bearing 7320 C3 bearing. The scope of work include supply of bearings and their replacements. Acceptable makes of bearings: SKF, FAG,NTN, NSK 5. Anabond thread sealing compound shall be applied to the thread of bolts to avoid loosening due to vibration. 6. Assembling of motor, painting of motor using two coats of anti-corrosive epoxy paint over suitable primer, conducting routine tests as per latest and relevant IS standards and No-load trial run at the rated voltage of 3.3 KV. 7. All test reports shall be submitted before dispatching the motor. The test results shall be in compliance with applicable standards / regulations etc. In case of deviations beyond acceptable values, they shall be brought to normal values by carrying out necessary corrective measures without any extra cost to FACT. 8. Routine tests including final no load trial run tests at rated speed and voltage shall be witnessed by FACT’s representative or FACT appointed third party at the contractors own testing facility. 9. The tests that has to be executed after the final assembly is listed in the special terms and conditons of contract. All test results will be approved as per the relevant IS standards only.

Stator core restacking: The work includes mounting the stator body in hydraulic press, removing the core pack from stator body with special tools and machineries after heating the stator yoke with special heating arrangements, segregating the damaged stator core from core pack, removing the old burnt core plate varnishes by chemical treatment, cleaning, removing the surface kinks, replacing damaged core stampings with new one, varnishing the stampings in re-varnishing cum conveyor oven to cure the core plate varnish, staggering the core with special tools and machineries, locking and repositioning the core pack to the stator body by hydraulic press and finally conducting the core flux test to ascertain the restacked core healthiness, cleaning and polishing the slots ready to feeding. Insulating and anti-corrosive coating shall be applied on slots, after cleaning. This work shall be executed after analyzing the stator flux loop test report, visual inspection and after getting approval from concerned engineer in charge. If partial re-staggering is only required, the payment will be done for only half the quantity mentioned. Note : This is an optional item and shall be carried out only after getting clearance from FACT Engineer-in-charge