HV MOTORS REWINDING

1. Coils Dismantling and Core 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 core are cleaned by combustion.

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

d) The core 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 Coil Head and the Connective Strap

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

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

3. Heaving of Coils

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

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

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

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

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

4.Coils Test

a) Each time when the coils 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 coil 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 coils, the top edges are descended in sequence following each heaving and the heaving operation is thus completed.

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

6. Making of Coils Connections

a) Coils seriations are made after the completion of coil 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 coil phase entry cables is performed by welding them on the coil 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 coils taken out from the kiln is performed by immersion or spraying method using kiln varnish.

c) The varnished coils 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
measured.

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 coil turn against each other.