Electricity: motive power systems – Synchronous motor systems – Pole changing motor winding circuits
Patent
1988-04-27
1989-09-12
Smith, Jr., David
Electricity: motive power systems
Synchronous motor systems
Pole changing motor winding circuits
318732, 318734, H02P 1912
Patent
active
048663646
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a circuit for changing poles of a rotor of a synchronous machine.
In many branches of industry in which electrical synchronous machines are utilized, it is necessary to change the poles of the rotors. This is particularly important in power plants. When certain hydraulic circumstances exist, e.g. during strong variations of the head or when utilizing the installation as a turbine and as a pump, it is in practice necessary for a turbine-generator assembly to be able to be driven at two different speeds. Alteration of the speed can be effected in an advantageous manner by altering the electrical pole number of the rotor.
As is known, changeover of the poles of the rotor of a synchronous machine is effected by reversing the direction of flow of the excitation current in the windings or coils of certain pole groups, while disconnecting other pole groups.
In the accompanying drawings:
FIGS. 1 and 2 show electrical circuits with and without poles to be disconnected, as are known from the state of the art;
FIG. 3 shows an electrical changeover circuit embodying the present invention; and
FIG. 4 shows an electrical circuit diagram of the changeover circuit according to the invention, with different connection and arrangement of the pole to be disconnected.
In order to change over only a single pole, it is necessary to employ four slip rings, as is illustrated by the circuits of FIG. 1.
The slip rings, which are indicated by reference numerals 1, are connected to reversible pole coils 2, and also to irreversible pole coils 3. Contact brushes 4 act on the slip rings 1 and are connected to an electrical current source indicated diagrammatically by reference numeral 5. An interrupter and reversing switch 6 is provided which, in practice, has the purpose of reversing the polarity of the source which is supplied to the poles and, thereby, of effecting changeover of the poles.
For the case in which, in addition to reversible poles, disconnectible poles are also provided it is for example necessary to employ five slip rings 1, as illustrated in the diagram of FIG. 2. In particular, the fifth slip ring is connected to disconnectible poles 7, which in turn are connected between the irreversible poles and the conductor between the irreversible poles and one of the slip rings 1.
In this case, also, there is provided an interrupter and reversing switch 6, which has the purpose of reversing the polarity of the current supplied for the reversible poles and, simultaneously, excluding the irreversible poles.
As can be seen from the drawings of the prior art arrangements, considerable constructional difficulties arise which can be ascribed to the large number of slip rings and the associated contact brushes. Furthermore, the fact must be taken into account that in the case of five slip rings, each ring to which no electrical current is provided is subjected to considerable wear. Difficulties therefore arise with respect to its replacement and its maintenance.
It is accordingly an object of the present invention to avoid the above-mentioned disadvantages and to provide a circuit for changing the poles of a rotor of a synchronous machine which enables the possibility that reversing and, in some circumstances, disconnecting poles can be effected using only two slip rings.
It is a further object of the invention to substantially simplify the construction of the electrical machine and, for that purpose, to ensure that the two slip rings employed are always supplied with an electrical current, whereby wear of the rings is substantially reduced.
A further object of the invention is to provide a reversing circuit which, in particular, is widely usable and offers the possibility of affecting a large number of constructionally different poles, whereby a further simplification of the machine construction is possible.
An additional object of the present invention is to provide a circuit for changing the poles of a rotor of a synchronous machine which offers the greatest possible accessibility and functional sec
REFERENCES:
patent: 1770871 (1930-07-01), Alger
patent: 3082364 (1963-03-01), Fischer et al.
patent: 4477760 (1984-10-01), Kuznetsov
Vogele, Hans; "Technik der Polumschaltung fur Pumpspechermaschinen grosser Leistung", Brown Boveri Mitteilungen, vol. 61, No. 7 (Jul. 1974), pp. 327-331.
Kontler Peter K.
Smith Jr. David
Tecnomasio Italiano Brown Boveri S.p.A.
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