Balancing of big rotors, processing of frames

Balancing of shaft vertical rotors – hydro („lens“ or lentils design) horizontal rotors – AC generators, synchronous rotors (rulers design) principle: –static balancing –dynamic balancing typical dimensions of rotors: –Hydrogen: up to 6 meters height, diameter 6-10 meters –Synchronous gen.: meters length!, diameter 1 meter (limited with the solidity of used steel) Note: some parts of rotor have nearly supersonic velocity!

Balancing of shaft Rotor „DANA“ is more than 60 m long (Nuclear power plant) Vibrations are limited and measured in 8 parallel plains (both static and dynamic balancing)

Balancing of shaft Centrifuge forces/moments, impact on life-time, Caused: by unbalanced mass (most often) oval bearings another reason Solution: add/remove the same mass from opposite site (weight/plumb). Typical material – „modeling clay“ Balancing: static dynamic (can be discovered just during rotation) mixed (both principles) Critical runs: unbalanced mass is on the opposite site

Special (long) rotors, turbo-rotors Auxiliary „bed“ (lunettes) Bending – unwanted, undesirable Issue of long rotors (10 m) Low-speed synchronous drivers –Accurate placing of poles –a lot of poles –RPM = 50 Hz / number of double-poles Poles – fixed by „dovetail“ lock

Turbo-rotors: groves: 9-12 mm width number: (divisible by 4) critical solidness: perimeter speed (circumferential speed) very high (100 m/sec), near to supersonic speed wedge: groves are fixed by bronze wedge

Machining of frames (AC drivers) „hard“ requirements –solidity –Parallelism of frontal surfaces –Perpendicularity (somewhere) –coaxially – aligned surfaces –deformation / not allowed Clamping –Important accuracy (< 0.1 mm) –Mechanical clamps –Electromagnetic clamps –Clamping of tools /induction heating/

Processing of frames Ageing – important for solidity, often are frames stored outside – climatic stress 1st. Basic issue – not rotating parts – difficult to machine 2nd. Basic issue – accuracy of clamping (fixing) minimizing of clamps: –Piece production: big work pieces – special tools and machines necessary –Serial production: often used machining centers with many tools and ONE clamp!

Processing of frames machining center horizontal and vertical tools one clamping table moving in 2 axis (X, Y) processing of frames must be discussed according: length x diameter!!!! (next slide)

1) Frames with length ~ diameter (L~D): Clamping from “inside” (frame – hatching part) 2) Frames with wide-body: D > L Clamping from front-side 1st. step: turning outside parts 2nd. step: turning inside parts 3rd. step – 4th. step: fixing and finishing rotor stack

Cutting of metal sheets/plates used in many procedures – rotor stacks, stator stacks, transformers, coils etc. Cutting machine – scissors/clippers Crowbar clip. (manually driven) Panel/board clip. (hydraulic, big stress) Disc/wheel clip. (sheets for transform.)

Drivers: for cutting: manual, hydro/pneumatic, eccentric principle Forces: up to 85% of tensile strength Very important: space (gap) between cutting edge (tool) and fixed form (shape) Technology issues of cutting