GB2266197A

GB2266197A - Voltage regulation in a generator

Info

Publication number: GB2266197A
Application number: GB9307458A
Authority: GB
Inventors: Guenter Minden; Klaus Vollmer; Guenter Waltke
Original assignee: Deutsche Aerospace AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1992-04-16
Filing date: 1993-04-08
Publication date: 1993-10-20
Also published as: DE4212906A1; FR2690291A1; GB9307458D0

Abstract

A generator comprises a stator (I) provided with a three-phase winding and a rotor (5) carrying permanent magnets (5a). The stator, or alternatively the rotor, is divided into two halves, which are rotatable relative to each other and coupled together by a rotational direction reversing gear (2). The gear can be operated to displace the two halves by the same amount but in opposite directions, so as to maintain a constant output voltage of the generator irrespective of load and rotational speed. <IMAGE>

Description

2266197 VOLTAGE REGULATION IN A GENERATOR The present invention relates to

a generator excited by permanent magnet means.

Generators of that kind have the disadvantage that the rotational speed dependence and load dependence of the voltage at their output terminals can be regulated out only by an electronic power unit dimensioned in accordance with the nominal rating of the generator.

There is thus a need for a generator which may allow a theoretically loss-free adjustment of the generator voltage so as to achieve a constant output voltage independent of load and of rotational speed.

According to the present invention there is provided a generator comprising a stator provided with winding means, a rotor excitable by permanent magnet means and having the same pole number as the stator, one of the stator and the rotor being axially divided into two relatively rotatable parts and the respective other one of the stator and the rotor being a single part, and means connecting said two parts together and operable to so angularly adjust these parts by relative rotation thereof as to effect regulation of the generator output voltage in a predetermined manner.

Preferably, said means is operable to rotationally displace said two parts by the same amount but in opposite rotational directions, and preferably comprises a rotational direction reversing gear transmission.

In one preferred embodiment the stator is divided into the said two parts and each part carries a respective three-phase current winding, corresponding sections of the windings being connected in series. In that case, the transmission can be carried in a stationary housing of the stator. In another preferred embodiment the rotor is divided into the said two parts and the stator carries a three-phase current winding In that case the transmission is carried in the rotor.

Embodiments of the present invention will now be more particularly described with reference to the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional view of a first generator embodying the invention, with two stator halves rotatable relative to each other; Fig. la is a partial cross-section of the generator of Fig. 1 along the line A-A of Fig. 1; Fig. 2 is a longitudinal sectional view of a second generator embodying the invention, with two rotor halves rotatable relative to each other; Fig. 2a is a partial cross-section of Fig. 2 along the line A-A of Fig. 2; and Fig. 3 is a pair of vector diagrams, in which the indice 1 indicates the first stator or rotor half of the generator of Fig. 1 or Fig. 2 and the indice 2 the second stator or rotor half of the generator.

Referring now to the drawings there is shown in Fig. 1 a generator which is excited by permanent magnets and which comprises a stator consisting of two identically constructed stator halves 1, which are rotatable relative to each other and carry a multi-stranded bipolar or multipolar three-phase current winding. The mutually corresponding winding strands of the two stator halves 1 are electrically connected in series. The stator halves are coupled together by way of a rotational direction reversing gear 2, axle bearings 3 of which are fixedly connected with a housing structure 4 of the generator. A unitary rotor 5 carrying a permanent magnet 5a associated with each stator half is arranged in the stator.

The reversing gear has in principle the effect that the torques transmitted from the unitary rotor 5 to the two stators 1 act counter to one another and therefore only the difference moment acts on the reversing gear 2. The difference moment is taken-up by a worm gear 6. A rotation of the two stator halves 1 relative to one another is undertaken by way of the reversing gear 2 if there is exerted on the worm wheel a torque with a magnitude resulting from the difference moment of the two stator halves 1, the accelerating moment of the masses of the stator halves and the frictional moment to be overcome, divided by the translation ratio of the worm gear. In the absence of reaction of the stator currents on the field distribution in the air gap, which is almost always possible with construction of the magnets in the rotor from Co-Sm or Nd-Fe-B, the moments transmitted from the rotor 5 on magnetic paths to the stator halves 1 are almost equal and the difference moment is small. In this case only the sum of the accelerating moment and the friction moment is to be exerted for the adjusting moment.

The voltage adjustment at the output terminals of the generator is based on the principle of vectorial addition of the sinusoidal part voltages induced in the two stator halves 1, as is evident from Fig.

3. In Fig. 3, 1 m signifies equivalence current of the magnets, Ia stator current, I U equivalent magnetising current, U i induced voltage, U R ohmic voltage drop, U b current-voltage drop, U 1 voltage of first stator half, U 2 voltage of second stator half and U 9 total voltage.

The indices 1 and 2 respectively signify the first stator half and the second stator half. If the rotational angle of the stator halves 1 relative to each other is zero, then voltages of like phase are induced in these; in total the algebraic addition of the part voltages arises and thus the natural maximum. The design of the generator thus has to be such that this case is present at minimum rotational speed and maximum load. If, however, the generator is operated only at part load or at a higher rotational speed, then a reduction of the sum of the two part voltages is necessary in order to keep constant the output voltage. This is possible if, by rotation of the stator halves 1 relative to each other, the two part voltages are no longer of like phase, but are added vectorially. -The particular advantage of this method consists in that with sinusoidal part voltages the sum voltage remains sinusoidally independent of the magnitude of the phase angle.

The relationship el = p mech is present between the mechanical adjustment angle -.mech and the phase angle el of the part voltages.

In this equation, p signifies the pole pair number of the generator.

Through spring biassing of the adjustment angle it can be ensured that the stable rest state of the adjustment angle is 180' el. Thus, in the case of breakdown of the regulating mechanism represented by the reversing gear and worm wheel only a minimum output voltage of the generator is present.

As to be seen from Fig. 2, relative rotation of rotor components - 5 is also possible as a means for influencing the output voltage of a generator excited by permanent magnet means. The generator shown in Fig. 2 comprises a stator 7 with a unitary lamination stack, which is fixedly connected with a housing structure of the generator and which has a laid-in multi-stranded bipolar or multipolar three-phase current winding 8. The generator further comprises a rotor which is divided at half length into two identical rotor halves 9, which carry permanent magnets 9a and are mounted to be rotatable relative to each other and which have a pole pair number matched to the stator 7. The two rotor halves 9 are coupled together by way of a reversing gear 10 arranged in the rotor, axle bearings 11 of the reversing gear being fixedly connected with a driven shaft of the rotor. Since the reversing gear is arranged in the rotating shaft, there is the necessity of having to transmit the adjusting moment to a rotating system, which for example is possible by way of an eddy-current brake 12. The effect of the reversing gear and the moment relationships correspond to the embodiment of Fig. 1. If a torque is exerted on the adjusting equipment represented by the eddy-current brake 12, then the two rotor halves 9 can be adjusted to a desired angle relative to each other.

In departure from the principle described for Fig. 1, the voltage adjustment in this case is based not on the principle of vector addition of part voltages, but on the principle of superimposition of magnetic part fluxes spatially displaced relative to each other. Also valid in this case are the angular relationships shown in Fig. 3 and therewith also the dependence of the output voltage of the generator on the torsion angle. An advantage of this principle resides in the omission of the coil ends between the stator halves in Fig. 1 and thus a saving in axial constructional length.

Claims

1 A generator comprising a stator provided with winding means, a rotor excitable by permanent magnet means and having the same pole number as the stator, one of the stator and the rotor being axially divided into two relatively rotatable parts and the respective other one of the stator and the rotor being a single part, and means connecting said two parts together and operable to so angularly adjust those parts by relative rotation thereof as to effect regulation of the generator output voltage in a predetermined manner.

2. A generator as claimed in claim 1, said means being operable to rotationally displace said two parts by the same amount but in opposite rotational directions.

3. A generator as claimed in claim 2, said means comprising a rotational direction reversing gear transmission.

4. A generator as claimed in any one of the preceding claims, is wherein the stator is divided into the said two parts and each of those parts carries a respective three-phase current winding, corresponding sections of the windings being connected in series.

5. A generator as claimed in claim 4 when appended to claim 3, wherein the transmission is carried by a stationary housing of the stator.

6. A generator as claimed in any one of claims 1 to 3, wherein the rotor is divided into the said two parts and the stator carries a three-phase current winding.

7. A generator as claimed in claim 6 when appended to claim 3, 5 wherein the transmission is carried in the rotor.

8. A generator comprising a stator divided into two substantially identically configured halves which are mounted in a stationary housing to be relatively rotatable and which each carry a three-phase current winding, mutually corresponding sections of the windings being connected in series, an undivided rotor excitable by permanent magnet means and having the same pole number as the -stator halves, and rotational direction reversing gear means interconnecting the stator halves and mounted in bearings carried by the housing, the gear means being actuable to effect angular adjustment of the stator halves is relative to the housing by the same amount but in different rotational directions.

9. A generator comprising a unitary stator carrying a three-phase currenting winding, a rotor excitable by permanent magnet means and divided into two halves which have a pole pair number matched to the stator and are mounted to be relatively rotatable, and reversing gear means interconnecting the rotor halves and mounted in bearings fixedly connected to a shaft of the rotor, the gear means being actuable to effect angular adjustment of the rotor halves relative to the stator by the same amount but in different rotational directions.

10. A generator substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

11. A generator substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.