Electromagnetic Design of a Solid Steel Rotor Motor for Demanding Operation Environments
Aho, Tuomo (2007)
Väitöskirja
Aho, Tuomo
2007
Acta Universitatis LappeenrantaensisURN:ISSN:1456-4491
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-214-499-7
https://urn.fi/URN:ISBN:978-952-214-499-7
Tiivistelmä
The solid-rotor induction motor provides a mechanically and thermally reliable solution for
demanding environments where other rotor solutions are prohibited or questionable. Solid
rotors, which are manufactured of single pieces of ferromagnetic material, are commonly used
in motors in which the rotationspeeds exceed substantially the conventional speeds of
laminated rotors with squirrel-cage.
During the operation of a solid-rotor electrical machine, the rotor core forms a conductor for
both the magnetic flux and the electrical current. This causes an increase in the rotor
resistance and rotor leakage inductance, which essentially decreases the power factor and the
efficiency of the machine. The electromagnetic problems related to the solid-rotor induction
motor are mostly associated with the low performance of the rotor. Therefore, the main
emphasis in this thesis is put on the solid steel rotor designs.
The rotor designs studied in thisthesis are based on the fact that the rotor construction should
be extremely robust and reliable to withstand the high mechanical stresses caused by the
rotational velocity of the rotor. In addition, the demanding operation environment sets
requirements for the applied materials because of the high temperatures and oxidizing acids,
which may be present in the cooling fluid. Therefore, the solid rotors analyzed in this thesis
are made of a single piece of ferromagnetic material without any additional parts, such as
copper end-rings or a squirrel-cage.
A pure solid rotor construction is rigid and able to keep its balance over a large speed range. It
also may tolerate other environmental stresses such as corroding substances or abrasive
particles. In this thesis, the main target is to improve the performance of an induction motor equipped
with a solid steel rotor by traditional methods: by axial slitting of the rotor, by selecting a
proper rotor core material and by coating the rotor with a high-resistive stainless
ferromagnetic material.
In the solid steel rotor calculation, the rotor end-effects have a significant effect on the rotor
characteristics. Thus, the emphasis is also put on the comparison of different rotor endfactors.
In addition, a corrective slip-dependent end-factor is proposed. The rotor designs
covered in this thesis are the smooth solid rotor, the axially slitted solid rotor and the slitted
rotor having a uniform ferromagnetic coating cylinder.
The thesis aims at design rules for multi-megawatt machines. Typically, mega-watt-size solidrotor
machines find their applications mainly in the field of electric-motor-gas-compression
systems, in steam-turbine applications, and in various types of largepower pump applications,
where high operational speeds are required. In this thesis, a 120 kW, 10 000 rpm solid-rotor
induction motor is usedas a small-scale model for such megawatt-range solid-rotor machines.
The performance of the 120 kW solid-rotor induction motors is determined by experimental
measurements and finite element calculations.
demanding environments where other rotor solutions are prohibited or questionable. Solid
rotors, which are manufactured of single pieces of ferromagnetic material, are commonly used
in motors in which the rotationspeeds exceed substantially the conventional speeds of
laminated rotors with squirrel-cage.
During the operation of a solid-rotor electrical machine, the rotor core forms a conductor for
both the magnetic flux and the electrical current. This causes an increase in the rotor
resistance and rotor leakage inductance, which essentially decreases the power factor and the
efficiency of the machine. The electromagnetic problems related to the solid-rotor induction
motor are mostly associated with the low performance of the rotor. Therefore, the main
emphasis in this thesis is put on the solid steel rotor designs.
The rotor designs studied in thisthesis are based on the fact that the rotor construction should
be extremely robust and reliable to withstand the high mechanical stresses caused by the
rotational velocity of the rotor. In addition, the demanding operation environment sets
requirements for the applied materials because of the high temperatures and oxidizing acids,
which may be present in the cooling fluid. Therefore, the solid rotors analyzed in this thesis
are made of a single piece of ferromagnetic material without any additional parts, such as
copper end-rings or a squirrel-cage.
A pure solid rotor construction is rigid and able to keep its balance over a large speed range. It
also may tolerate other environmental stresses such as corroding substances or abrasive
particles. In this thesis, the main target is to improve the performance of an induction motor equipped
with a solid steel rotor by traditional methods: by axial slitting of the rotor, by selecting a
proper rotor core material and by coating the rotor with a high-resistive stainless
ferromagnetic material.
In the solid steel rotor calculation, the rotor end-effects have a significant effect on the rotor
characteristics. Thus, the emphasis is also put on the comparison of different rotor endfactors.
In addition, a corrective slip-dependent end-factor is proposed. The rotor designs
covered in this thesis are the smooth solid rotor, the axially slitted solid rotor and the slitted
rotor having a uniform ferromagnetic coating cylinder.
The thesis aims at design rules for multi-megawatt machines. Typically, mega-watt-size solidrotor
machines find their applications mainly in the field of electric-motor-gas-compression
systems, in steam-turbine applications, and in various types of largepower pump applications,
where high operational speeds are required. In this thesis, a 120 kW, 10 000 rpm solid-rotor
induction motor is usedas a small-scale model for such megawatt-range solid-rotor machines.
The performance of the 120 kW solid-rotor induction motors is determined by experimental
measurements and finite element calculations.
Kokoelmat
- Väitöskirjat [999]