1. Coils Dismantling and Nucleus Cleaning

a) Old coils are detached from the cavities by the help of wedges and crank levers

b) Isolation materials and varnish residues remaining in the nucleus are cleaned by combustion.

c) The interior sections of the nucleus and the endocavity are purged of their burrs by sandpapering.

d) The nucleus is subjected to magnetic heating test. In case no problems occur, it is
rendered ready for winding by dyeing with prime paint. Partial or completion is
performed on it if problems occur.

2. Installation of the Bobbin Head and the Connective Strap

a) Iron bars in sufficient thickness are rounded and prepared according to the OG bobbin dimensions and these bars are attached to the engine trunk by welding.

b) The rounds are isolated with isolation materials in sufficient thickness.

3. Heaving of Bobbins

a) Guide bands are used in order that the fully conductive bands, which are wrapped around the bobbin for corona losses during the installation of the bobbins on the cavity, are not damaged.

b) The bobbin heads are fastened around the strap with polyglass band and their resistance is thus increased against electromagnetic loads.

c) The bobbins are connected to each other by reinforcing the intervals between the bobbin heads by felts and chocks.

d) Glass laths that support the appropriate compression of the bobbins are placed in cavity bases, bobbin intervals and over the cavities.

e) PT100 heat detector is placed between the bobbin intervals for each phase.

4. Bobbin Test

a) Each time when the bobbins are heaved into the cavity, they are subjected to 1 minute test with AC High Voltage after their connections are made. By this test, it is checked whether the bobbin was damaged during heaving or connection; or whether any problem exists concerning its production or the relevant isolation; and whether problems are present in the full-conductor or semiconductor corona bands. Application voltage is 2xU +1000 Volts.

5. Pitch Lifting

a) Inorder to heave the final bobbins, the top edges of several bobbins, the number of which equal to the that of a pitch, are taken from inside of the cavity and by using a silk band, they are fastened and later lifted upwards in a manner that they remain constant overhead. During the heaving of the bobbins, the top edges are descended in sequence following each heaving and the heaving operation is thus completed.

b) The bobbins are firmly fixated by hammering glass or magnetic laths in the cavities.

6. Making of Bobbin Connections

a) Bobbin seriations are made after the completion of bobbin heaving. For this purpose, copper wire terminals are joined over each other, welding that contains silver additive is made and their isolations are completed by wrapping their outer surfaces.

b) The isolation of bobbin phase entry cables is performed by welding them on the bobbin phase terminals.

c) All terminals all firmly bound with each other with chocks, felts and polyglass bands and the winding operation is thus completed.

7. Kiln-Drying and Varnishing

a) The stator is kiln-dried by subjecting its entirety to a heating up to 130 °C for a period of 15 hours.

b) The varnishing of the stator bobbins taken out from the kiln is performed by immersion or spraying method using kiln varnish.

c) The varnished bobbins are placed in the kiln and dried there by heating up to 130 °C for a period of 15 hours.

8. Final Tests

a) Megger Test: The isolation values of the phases against the chassis and each other are

b) DC resistance test: Their DC resistances are measured by the application of maximum 15 amperes and on 1/10000 sensitivity level.

c) HI-POT & SURGE Test: HI-POT test is performed for checking the high-voltage resistance of the phases against the chassis and each other whereas SURGE test is performed for measuring the high-voltage resistance of the bobbin spirs against each other.