Download Manufacturing of electrical machines – 1. Lecture

Shafts for rotating machines
Sorting of rotating el. machines
• According power • Ac. principle
– Small < 10 kW
– middle-class
up to 1 MW
– big (not correctly
specified)
–
–
–
–
DC
asynchronous
synchronous
Alternative,
ECM etc.
• Ac. application
- traction,
- crane, slow/fast
rotating
- compressors,
- explosion-proof,
etc.)
Sorting of non-rotating machines
(especially chokes, transformers, elmag. chucks)
• Ac. power and
• Ac. design, assembly • Acc. application
voltage
– power plants
– air (transformers)
– low-power, up to
– traction
– oil based
10 kW
– ovens/furnaces
– special (auto– middleclass, up to
transformers,
– electrochemical
1 MW
regulating tr., etc.)
– Etc.
– big
Modern trend – increase of operating temperature (class „F“) very
popular (190°C)
Characterization of production flow
Piece production
– product = big machines or
technology element
– layout designed according
technological requirements
– special production
machines and templates
are used
– exacting preparation of
production and high
requirements on the staff –
qualifications!
Mass-production
– product = small machines
– layout according production
flow!
– Often single-usage technology
equipment (machines)
– just for one operation
– using of „lines“ layout
– more automation
– lower requirements of staff qualification
Manufacturing of shaft
Issue: strength, precision of mechanical
turning, dimensions acc. standards
Initial material:
• rolled- steel rod up to  150 mm
• steel rod calibrated up to  70 mm
(for mass-production)
• forged ingot, heated and hammered
Note: Quality of material is checked, some off-takes
are done and analyzed
Hammered shaft – production
procedure
• casting (founding) – ingots with double mass
• hammering – at circa 700 °C
• pre-heating (possible)
• annealing - 700 - 800 °C (also „tempering), changing of
hardness and mechanical properties
• axis hole – off-taking of samples, analysis, also space for
winding or cooling
Tests of mechanical parameters.: visual, DC current,
ultrasonic, etc.
Mechanical turning of shafts
•
•
•
•
Rolling – between two rollers, presses
Splitting – scissors, sawmill, flame-cutting
Clamping – centering by axis-hole
Mechanical turning:
– Rough turning (big tolerance)
– Finishing of surface (précising) – pads for bearings
Issues: using of more tools, troubles with clamping and accuracy.
Today popular clamping with magnetic chucks or induction
heating.
Cutting of grooves – sometimes by turning, more often by milltool.
Steps of mechanical turning
Finishing of surfaces (polishing)
Sorting of shafts
• smooth (plain) shafts – small machines
• graded shafts (terrace) profile
• shaft with flange – just for rolling-bench
• special design – shaft made from segments
• special surface – grooving – for small machines
Fixing rotor plates on shafts
Plain shaft
Plain shaft with
grooves (fixing)
Plain shaft with
grooves and ruler
Shaft made from
segments – fixing
with „locks“
Complete process of mass production of
shafts for small drivers
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:
– hydro generator: up to 6 meters height, diameter 6-10
meters,
– synchronous generators: 10-12 meters length, diameter
up to 1 meter (limited with the solidity of used steel).
Note: some parts of the rotors have nearly the supersonic velocity!