Magnetic gearing of permanent magnet brushless motors
A permanent magnet brushless 3-phase motor comprises windings R, Y, B, each divided into a plurality of sections 1 - 5 and switch means S 1 -S 12 for selectively connecting the section of the respective winding e.g. R in series and/or parallel with all other sections of that winding R. Control means are provided for actuating the switch means S 1 -S 12 to connect the winding sections 1 - 5 in different configurations while the motor is running to alter the speed/torque characteristics of the motor.
1. A permanent magnet brushless motor comprising:
a stator comprising one or more phases, wherein at least one given phase of the stator includes a plurality of winding sections;
a rotor rotatably mounted relative to the stator and comprising at least one permanent magnet; and
switch means comprising a plurality of switching devices for simultaneously connecting all of the winding sections of the given phase in one of a plurality of different configurations, wherein said switching devices are disposed at opposite ends of each winding section and are arranged to connect each winding section in series and/or parallel with all other winding sections of the given phase.
2. A permanent magnet brushless motor as claimed in claim 1 , wherein:
the switch means is arranged to connect all of the winding sections of the given phase in parallel.
3. A permanent magnet brushless motor as claimed in claim 1 , wherein:
the switch means is arranged to connect all of the winding sections of the given phase in series.
4. A permanent magnet brushless motor as claimed in claim 1 , wherein:
the switch means is arranged to connect some of the winding sections of the given phase in parallel, with at least one other winding section of the given phase being connected in series with the parallel-connected winding sections.
5. A permanent magnet brushless motor as claimed in claim 1 , wherein:
the voltage applied to the winding sections of the given phase is pulse-width modulated.
6. A permanent magnet brushless motor as claimed in claim 5 , wherein:
the voltage applied to the winding sections of the given phase is pulse-width modulated by selectively energising said switch means.
7. A permanent magnet brushless motor as claimed in claim 1 , further comprising:
means for repeatedly actuating said switch means to change said winding sections between different connection configurations to obtain a motor characteristic intermediate that of the connection configurations between which the winding sections are repeatedly switched.
8. A permanent magnet brushless motor as claimed in claim 1 , further comprising:
control means for actuating the switch means to vary the connection configuration of the winding sections whilst the motor is running, in accordance with predetermined operating parameters.
9. A permanent magnet brushless motor as claimed in claim 8 , wherein:
the control means is adapted to vary the connection configuration of the winding sections whilst the motor is running, in accordance with the output of means for sensing an operating parameter of the motor.
10. A permanent magnet brushless motor as claimed in claim 8 , wherein:
the control means is adapted to vary the connection configuration of the winding sections whilst the motor is running, in accordance with the output of means for sensing an operating parameter of the article being driven by the motor.
11. A permanent magnet brushless motor as claimed in claim 8 , wherein:
the control means is adapted to vary the connection configuration of the winding sections of a conducting phase whilst the motor is running, in accordance with the back emf measured across a non-conducting phase or a winding section thereof.
12. A permanent magnet brushless motor as claimed in claim 8 , wherein:
the control means is adapted to vary the connection configuration of the winding sections whilst the motor is running, in accordance with time or an operating cycle or program.
13. A permanent magnet brushless motor as claimed in claim 8 , wherein:
the control means comprises means for manually changing the connection configuration of the winding sections.
14. A permanent magnet brushless motor as claimed in claim 1 , wherein:
all of the winding sections of the given phase are wound in parallel to each other.
15. A permanent magnet brushless motor as claimed in claim 1 , wherein:
the winding sections of the given phase are connected such that current flows through each winding section in the same direction.
16. A permanent magnet brushless motor as claimed in claim 1 , wherein:
one of the winding sections of the given phase comprises a different number of turns from another winding section of the given phase.
17. A permanent magnet brushless motor as claimed in claim 1 , wherein:
one of the winding sections of the given phase comprises a conductor having a different cross-sectional area than the conductor of another winding section of the given phase.