Presentation on theme: "Windings for stators and rotors. Winding for stators – AC machines Possible types of windings: According way of insertions in holes/grooves: –axial layout."— Presentation transcript:
Winding for stators – AC machines Possible types of windings: According way of insertions in holes/grooves: –axial layout –radial layout According shape of wires: –circular (formed after insertion into grooves) –special profile (formed before insertion) According number of layers: –single-layer –double-layer
Winding for small drivers (mass- production) up to 500 kW Limited by voltage 1 kV: circular cooper wire cca up to 2 mm dispersed winding – cheap fro production, low efficiency of volume of groove, unknown voltage between turns Higher than 1 kV: winding made from profiled wires – better efficiency of grooves production process - less automation Winding-machines: complicated movement of arm – for dispersed winding Pulling of wires – for profiled wires
Production process wires are wind-up on templates (via machines, not manually!) covering of grooves (textile foil) – isolation function dispersing/scattering of wires fixing of wires by wedges connection of wires at front sides (critical point) binding/bandages – especially at front sides Critical issue: bandages x isolation x mechanical properties Impregnating process of bandages: –drying (at temperature about 130 °C) –plunging bandages into solvent (40 °C) –hardening event. second impregnation
Winding for high voltage drivers typically up to 6 kV - profiled wires forming of turns before assembly grooves – often „opened“, not „closed“ winding – contains integrated isolation system isolation - based on mica (isinglass) isolation – resistance up to 3 kV/mm of electrical stress/intensity Difficult issue: mechanical properties and stress of isolation during forming of turns!
3 – isolation layer 4 – separation layer or wedge 1 – longitudinal part of turn 2 – front-side parts
View of front side part of stator winding – big AC generator, 6,0kV winding
Winding from rod/bars (artificial Roeble’s rods/bars) Principle: parallel wires are permutated lower power-losses due to whirling currents Processing of rods: Forming of wires Assembly of rods (including isolation spacing) Hardening (including of isolation or cement between copper parts) Variants of cooling: Compressed-air cooling (big cross-section of channel), difficult process of forming of turns Liquid-based cooling (hollow tubes)
outlets/ connection longitudinal isolation - diameter of turning - „nose“ - front-side parts Formed single turn for 6,0kV stator
Different channels for cooling systems Cross-section of stator rod with separated/spitted channels Cross-section of stator rod for water (liquid) cooling
Fixing of rods in grooves (1) and (4) Different shapes and cross- sections (2), (3), (5), (6)
Detail of front-side parts for 6,0kV driver Isolation desk/board Separation foil rope from hemp (plant) damping circle Isolation desk/boardCarrier of winding
Protection against partial discharges Basic cause (root cause) not-fixed isolation on wires cavity in isolation material non-homogenous grooves Examples of solving: (synthetic) resin with small particles of graphite („smola“) hardening of isolation system in hot-press or vacuum chambers conductive layer (painting or foil) on the surface of isolation or on the surface of grooves Special issue: output of wires from grooves – semi conductive layer (painting)
Important issues: small tolerance 0,5 mm mechanical solidity filling of cavities by graphite paper Solution: isolation desks/boards axial wedges fixture/brace circles Assembly of winding Very important – mechanical solidity of front-side parts!!!
Winding of rotors of induction (AC) drivers Smaller drivers: winding made from coils dispersed /not oriented winding or Squirrel-cage rotor: The motor rotor shape is a cylinder mounted on a shaft. Internally it contains longitudinal conductive bars (usually made of aluminum or copper) set into grooves and connected at both ends by shorting rings forming a cage-like shape. The name is derived from the similarity between this rings-and-bars winding and a squirrel cage. Bigger drivers: rods with full cross-section (copper) –dispersed (not often), –axially inserted (more often).
Rotors for AC drivers – squirrel cage Small drivers: pouring-off Mass production pouring-off (forms, 40 MPa) preheating, melting, pouring-off, cooling Piece production pouring into mould form (ingot) –preheating up to (500 °C) Advantage Pouring-off enables to make different and difficult shapes of grooves (double cage etc.) Everything is still based on ALUMINUN – Al !!!
Groves for start-up (ramp-up) Profiled grooves – different distribution of current density Double cage called „Boucherot“
Shapes of grooves for AC induction drivers for stators for rotors for hard ramp-up (start-up)
Filling of grooves on rotor by stacks of winding
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