Abstract
For large synchronous machines, the excitation is usually provided by a DC-fed field winding in the rotor. For small synchronous machines, however, this is undesirable, on the one hand because of the complications for supplying DC to the rotor (i.e. slip rings, rectifier), on the other hand because the smaller the dimensions, the less efficient a field winding is in producing a magnetic flux.
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Notes
- 1.
From scaling laws, it can be shown [21] that the ratio of the volumes of material required for permanent magnet excitation to that for DC excitation varies proportionally to the pole pitch; thus for smaller power ratings, permanent magnet excitation allows for a smaller machine.
- 2.
In practice, a machine will always have an already stabilised operating point at delivery.
- 3.
Note that also disassembling and removing the rotor from the stator without magnetically short-circuiting the rotor will result in an irreversible reduction of the induction.
- 4.
When the reluctance of the iron core is not negligible, this reluctance must be added in the denominator of Eq. 20.13.
- 5.
Cf. Reluktanzmotoren kleiner Leistung, Hans-Joachim Gutt; Etz-Archiv, Bd.10, 1988, H.11, pp. 345–354.
- 6.
How do the absolute values of the reactances vary with the pole pitch? Remember the variation of the rated impedance \(Z_{n}\) with the pole pitch for induction machines.
- 7.
J.K. Kostko, Polyphase reaction synchronous motors, JAIEE, 1923, pp. 1162–1168.
- 8.
Why is the loss proportional to |s| and not simply s?
- 9.
The dimensions shown are micrometers.
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Melkebeek, J.A. (2018). Small Synchronous Motors. In: Electrical Machines and Drives. Power Systems. Springer, Cham. https://doi.org/10.1007/978-3-319-72730-1_20
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DOI: https://doi.org/10.1007/978-3-319-72730-1_20
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