GB2093640A

GB2093640A - A variable speed drive unit

Info

Publication number: GB2093640A
Application number: GB8100890A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-01-13
Filing date: 1981-01-13
Publication date: 1982-09-02

Abstract

A variable speed drive unit, of the kind in which the output speed varies according to the output load, comprises a rotatable field alternator and a rotatable armature alternator mechanically coupled by a common shaft (1) and a common carcass in the form of a cylinder (7) and electrically coupled via rectifier units fixed respectively to the shaft and to the cylinder (7). The cylinder is free to rotate on supporting bearings (16) and supports a wound stator core (8, 9) of the field alternator. The shaft (1) is supported by bearings (13) and has attached to it at least one pair of poles (2) surrounded by field coils (3) of the field alternator. The shaft (1) also carries a rotor core (4) on which are wound coils (5) of the armature alternator. Field coils (11) on pole pieces (12) are mounted on the cylinder (7) and are connected to the windings (9) of the stator (8) via rectifiers (10). The windings (5) of the rotor (4) are connected to the field coils (3) via rectifiers (6). A shaft (15) is rigid with one of the bearings (16) and, if the shaft (1) is driven, constitutes an output shaft. On the other hand, the shaft (15) may comprise an input shaft if the shaft (1) is to be the output. <IMAGE>

Description

SPECIFICATION A variable speed drive unit This invention relates to a variable speed drive unit of the kind in which the output speed varies according to the output load. For any given input speed, the output speed will decrease as the load increases and increase as the load decreases.

According to the invention a unit of the kind referred to comprises a revolving field alternator and a revolving armature alternator, mechanically coupled by a common shaft and a common carcass (which is free to revolve on supporting bearings) and electrically coupled via rectifier units fixed respectively to the shaft and to the carcass.

How the invention may be put into practice appears from the following description with reference to the accompanying drawings, in which a unit according to the invention is illustrated schematically and by way of example, Figure 1 being a longitudinal sectional elevation of the unit; Figure 2 a view in section on the line A-A of Fig. 1; and Figure 3 a view in section on the line B-B of Fig. 1.

In the illustrated unit a shaft 1 is supported by bearings 1 3 and has attached to it an electromagnetic field system consisting of one or more pairs of poles 2 surrounded by field coils 3 (there would normally be one field coil per pole but it could be more convenient to use one field coil per pair of poles).

Also attached to the shaft 1 is a rotor core 4 of circular formation, having slots near the periphery and parallel to the shaft, into which slots are inserted coils 5 of insulated conductors i.e. similar to the rotor of a wound rotor motor or a revolving armature alternator.

A carcass comprises an outer cylinder 7 having end-plates 14 with bearing journals 1 6 to be supported in a machine frame or other means (not shown) and supports a wound stator core 8 and 9 which is similar to the stator of a normal squirrel cage motor or revolving field alternator. Also supported by the cylinder 7 is a field system 11 and 12. A shaft 1 5 is rigid with one of the journals 16.

When the shaft 1 is driven and revolves relative to the cylinder 7 the magnetic poles 2 induce an electro-magnetic force in the windings 9 of the stator 8. The output from this circuit is fed through a rectifier assembly 10 to the field coils 11 on the pole pieces 1 2.

The magnetic field thus created induces an electromagnetic force in the windings 5 of the rotor 4 and this energises the field coils 3 of poles 2 via the rectifier units 6.

Thus, the greater the relative speed of the input shaft 1 to the cylinder 7, the greater the field strength and thus the torque exerted on the output shaft 1 5.

Alternatively the shaft 1 5 may be the driven input shaft, and then the shaft 1 is the output shaft.

In order to initiate the electromagnetic system, it is necessary to produce a magnetic field in one, or both, of the field systems. This can be accomplished by: (a) Incorporating a permanent magnet in one or more of the pole pieces, or (b) Passing a direct current through one or more of the field coils, prior to assembly and using the residual field, or (c) Magnetising one or both field systems by an external magnetisier after assembly.

Leads may be brought out to slip rings or other current collecting devices to enable a variable resistance or other current controlling device to be connected in series with the field coils of either or both of the electromagnetic field systems. This enables the field current to be controiled which in turn controls the output speed for a given torque or the output torque for a given speed.

The drawings illustrate one advantageous construction by way of example, but many modifications are possible within the scope of the invention, for example it would be possible to have one or each of the field systems at one side of the respective rotor instead of surrounding it.

1. A variable speed drive unit of the kind in which the output speed varies according to the output load, said unit comprising a rotatable field alternator and a rotatable armature alternator, mechanically coupled by a common shaft and a common carcass, which is free to rotate on supporting bearings, and electrically coupled via rectifier units fixed respectively to the shaft and to the carcass.

2. A variable speed drive unit according to claim 1, wherein the carcass comprises a cylinder surrounding the alternators and arranged to drive an output shaft when said common shaft is driven.

3. A variable speed drive unit according to claim 1, wherein the carcass comprises a cylinder surrounding the alternators and arranged to impart drive to the said common shaft when driven by an input shaft to which it is connected.

4. A variable speed drive unit according to claim 2 or claim 3, wherein the cylinder is provided with end plates mounted on said supporting bearings on the said common shaft and wherein the output or input shaft is connected to one of the end plates on the outer surface thereof.

5. A variable speed drive unit according to any preceding claim, wherein the carcass supports a wound stator core of the rotatable field

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A variable speed drive unit This invention relates to a variable speed drive unit of the kind in which the output speed varies according to the output load. For any given input speed, the output speed will decrease as the load increases and increase as the load decreases. According to the invention a unit of the kind referred to comprises a revolving field alternator and a revolving armature alternator, mechanically coupled by a common shaft and a common carcass (which is free to revolve on supporting bearings) and electrically coupled via rectifier units fixed respectively to the shaft and to the carcass. How the invention may be put into practice appears from the following description with reference to the accompanying drawings, in which a unit according to the invention is illustrated schematically and by way of example, Figure 1 being a longitudinal sectional elevation of the unit; Figure 2 a view in section on the line A-A of Fig. 1; and Figure 3 a view in section on the line B-B of Fig. 1. In the illustrated unit a shaft 1 is supported by bearings 1 3 and has attached to it an electromagnetic field system consisting of one or more pairs of poles 2 surrounded by field coils 3 (there would normally be one field coil per pole but it could be more convenient to use one field coil per pair of poles). Also attached to the shaft 1 is a rotor core 4 of circular formation, having slots near the periphery and parallel to the shaft, into which slots are inserted coils 5 of insulated conductors i.e. similar to the rotor of a wound rotor motor or a revolving armature alternator. A carcass comprises an outer cylinder 7 having end-plates 14 with bearing journals 1 6 to be supported in a machine frame or other means (not shown) and supports a wound stator core 8 and 9 which is similar to the stator of a normal squirrel cage motor or revolving field alternator. Also supported by the cylinder 7 is a field system 11 and 12. A shaft 1 5 is rigid with one of the journals 16. When the shaft 1 is driven and revolves relative to the cylinder 7 the magnetic poles 2 induce an electro-magnetic force in the windings 9 of the stator 8. The output from this circuit is fed through a rectifier assembly 10 to the field coils 11 on the pole pieces 1 2. The magnetic field thus created induces an electromagnetic force in the windings 5 of the rotor 4 and this energises the field coils 3 of poles 2 via the rectifier units 6. Thus, the greater the relative speed of the input shaft 1 to the cylinder 7, the greater the field strength and thus the torque exerted on the output shaft 1 5. Alternatively the shaft 1 5 may be the driven input shaft, and then the shaft 1 is the output shaft. In order to initiate the electromagnetic system, it is necessary to produce a magnetic field in one, or both, of the field systems. This can be accomplished by: (a) Incorporating a permanent magnet in one or more of the pole pieces, or (b) Passing a direct current through one or more of the field coils, prior to assembly and using the residual field, or (c) Magnetising one or both field systems by an external magnetisier after assembly. Leads may be brought out to slip rings or other current collecting devices to enable a variable resistance or other current controlling device to be connected in series with the field coils of either or both of the electromagnetic field systems. This enables the field current to be controiled which in turn controls the output speed for a given torque or the output torque for a given speed. The drawings illustrate one advantageous construction by way of example, but many modifications are possible within the scope of the invention, for example it would be possible to have one or each of the field systems at one side of the respective rotor instead of surrounding it. CLAIMS

5. A variable speed drive unit according to any preceding claim, wherein the carcass supports a wound stator core of the rotatable field alternator and wherein the said common shaft carries at least one pair of poles surrounded by at least one field coil of said field alternator.

6. A variable speed drive unit according to claim 5, wherein a permanent magnet is incorporated in at least one of the pole pieces.

7. A variable speed drive unit according to claim 5, wherein a magnetic field is produced in the field system by passing a direct current through one or more of the field coils prior to assembly.

8. A variable speed drive unit according to claim 5, wherein a magnetic field is produced in the field system after assembly by means of an external magnetiser.

9. A variable speed drive unit according to any preceding claim, wherein the carcass supports a field system of the rotatable armature alternator and wherein the said common shaft carries a rotor core on which are mounted coils of said armature alternator.

10. A variable speed drive unit according to claim 9, wherein the rotor core has a circular cross-section with slots in the periphery extending substantially parallel to the common shaft, said coils in the form of insulated conductors being inserted in said slots in the rotor core.

11. A variable speed drive unit according to claim 9 or claim 10 when appended to any one of claims 5 to 8, wherein the windings of the stator core of the rotatable field alternator are electrically connected to field coils on pole pieces of the field system of the rotatable armature alternator via rectifiers.

12. A variable speed drive system according to claim 11, wherein the coils on the rotor core of the rotatable armature alternator are connected to the field coil(s) of the rotatable field alternator via at least one rectifier.

1 3. A variable speed drive unit according to any preceding claim, wherein current controlling means are connected in series with the field coils of either or both of the alternators.

14. A variable speed drive unit according to claim 13, wherein the current controlling means comprise one or more variable resistances.

1 5. A variable speed drive unit substantially as described herein with reference to the drawings.