Brushless rotating electrical machine

• US 5,059,876 A
• Filed: 12/12/1989
• Issued: 10/22/1991
• Est. Priority Date: 12/10/1987
• Status: Expired due to Fees

• Current Assignee: Andre K. Agassi
• Original Assignee: Emanuel E. Shah
• Inventors: Shah, Emanuel E.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US07/448,990
• Time in Patent Office: 679 Days
• Field of Search: 318/138, 318/254, 318/700, 318/705, 318/712, 318/715, 318/716, 318/720, 318/721, 318/722, 310/91, 310/156, 310/261, 310/268
• US Class Current: 318/400.09
• CPC Class Codes: H01F 38/18 Rotary transformers
• CPC Class Codes: H02K 29/06 with position sensing devices H02K29/03 takes precedence
• CPC Class Codes: H02P 6/14 Electronic commutators
• CPC Class Codes: H02P 9/302 Brushless excitation

Abstract

A brushless rotating electrical machine based on a novel rotatable transformer. The motor can operate on both AC or DC. The rotatable transformer, termed brushless power unit, transfers power to the rotating armature without any physical contact and the operation of the brushless power unit is independent of speed of armature. A sensor on the armature detects the position of the armature coils in relation to magnetic neutral axis and switches semiconductor switching devices located on the armature to reverse the direction of current in the armature coils to commutate the current and produce a continuous torque. The electronic commutation is also applied to polyphase AC machines to obtain brushless operation. DC excitation system for synchronous machines can obtain brushless operation using the brushless power unit.

Claims

1. A brushless rotating electrical machine for transferring power and having a shaft, comprising:

a rotor member means attached to the machine shaft and includes at least one rotor coil means and a rotor magnetic path means, wherein said rotor coil means is magnetically coupled to said rotor path means and the axis of said machine shaft passes through said rotor coil means;

a stator member means includes at least one stator coil means;

a stationary yoke member means made up of magnetic flux conducting material which forms at least one air gap with the rotor magnetic path means, said stationary yoke member means completes a closed magnetic circuit mutually coupling said rotor means and said stator coil means, said stationary yoke member means is disposed so as too allow free relative motion of said rotor member means with respect to said stator member means and said stationary yoke member means;

said stator member means magnetically couples with said rotor member means in such a way that said stator coil means and said rotor coil means overlap each other and the magnetic circuit is completed by said stationary yoke member means and said at least one air gap; and

means for applying time variant voltage to the coil means of one of said member means, wherein a voltage is induced in the coil means of the other of said member means by virtue of mutual magnetic coupling between the coil means of the two member means and power is transferred from one member means to the other member means for use in said brushless rotating electrical machine.

2. The brushless rotating electrical machine as claimed in claim 1 wherein said stator member means magnetically couples said rotor member means through said stationary yoke member means, said rotor magnetic path means is made up of magnetic flux conducting material and passes through said rotor coil means and said stator coil means, and wherein said stator coil means is located in such a way that the magnetic circuit is closed by said stationary yoke member means passing through said stator coil means and by at least two air gaps.

3. The brushless rotating electrical machine as claimed in claim 1 wherein said rotor magnetic path means comprises a spirally wound sheet of magnetic flux conducting material around the machine shaft making up a cylindrical structure in which the flux travels along the axis of the machine shaft.

4. A brushless rotating electrical machine for transfer of power and having a shaft, comprising:

a rotor member means attached to the machine shaft and includes at least one rotor coil means and a rotor magnetic path means, wherein said rotor coil means is magnetically coupled to said rotor magnetic path means;

a stator member means includes at least one stator coil means, wherein the axis of the machine shaft passes through said stator coil means;

a stationary yoke member means forms at least one air gap with said rotor magnetic path means, said stationary yoke member means completes a closed magnetic circuit mutually coupling said rotor coil means and said stator coil means, and said stationary yoke member means is disposed so as to allow free relative motion of said rotor member means with respect to said stator member means and said stationary yoke member means;

said stationary yoke member means comprises a cylindrical structure occupied by a means capable of carrying magnetic flux and is characterized by a hollow cylinder made up of spirally wound sheet of magnetic flux conducting material;

at least one rotating member attached to the machine shaft and forms said rotor magnetic path means by linking magnetic flux from one end of said cylindrical structure to the other end; and

means for applying time variant voltage to the coil means of one of said member means, wherein a voltage is induced in the coil means of the other of said member means by virtue of mutual magnetic coupling between the coil means of the two member means and power is transferred from one member mans to the other member means for use in said brushless rotating electrical machine.

5. The brushless rotating electrical machine as claimed in claim 4 wherein said stator coil means is wound around said stationary yoke member means making up said cylindrical structure in which the flux travels along the axis of said machine shaft.

6. A brushless rotating electrical machine having a shaft, comprising:

an armature magnetic path means;

a motor armature means attached to the machine shaft and includes a plurality of coils located in a plurality with slots, said motor armature means is magnetically coupled to said armature magnetic path means;

a motor field member means includes a field pole means having a plurality of magnetic poles of opposite polarity with inner polar region located between two poles of opposite polarity, and is further disposed so as to receive said motor armature means which is able to be freely rotated inside the motor field member means, said rotor field member means includes a field magnetic path means;

means for transferring power between a rotating member attached to the motor armature means and a stationary member attached to the motor field member means, said stationary member and said rotating member forming a brushless power unit;

a timing and control unit for directing and controlling a power transfer between a source of power located on the machine shaft and the coils of said motor armature means, said timing and control unit comprises;

(1) a plurality of semiconductor switching devices connected between the coils of said motor armature means and said source of power, wherein said semiconductor switching devices drive the current through the coils of said motor armature means in desired direction by selectively switching said semiconductor switching devices into conduction and out of conduction;

(2) means for generating commutation signals, including a means for detecting the relative position of the coils of the motor armature means with respect to some unique region on the field pole means characterized by a neutral axis between the two opposite field poles, wherein said commutation signals selectively control the semiconductor switching devices, located on the motor armature means, in proper sequence to reverse the direction of current in the coils of said motor armature means at a desired point of rotation in order to effect commutation and thereby generating a required electromechanical action between the motor armature means and the motor field member means; and

(3) a rectifier unit for supplying DC power to the coils of said motor armature means for DC operation.

7. The brushless rotating electrical machine as claimed in claim 6 wherein aid means for generating commutation signals comprises:

a position sensor means and a means to activate the same, wherein said position senor means defines an angular position of said motor armature means by communicating a predetermined logic level to said semiconductor switching devices, to switch a required voltage to the coils of the motor armature means in a selected direction to produce a required torque; and

a shaft position encoding means interposed between said position sensor means and said means to activate the same, wherein said position encoding means controls the timing relationship of the commutation signals produced by sad position sensor means by controlling the action of said means to activate the same on the position sensor means to a predetermined logic truth table determined by the relative position of the position sensor means with respect to some unique region on the motor armature means characterized by the neutral axis between the two field pole means and thereby accurately controlling the switching time and the direction of current flow in each coil of said motor armature means.

8. The brushless rotating electrical machine as claimed in claim 6 wherein said field pole means comprises a means to create magnetic flux including a permanent magnet and a coil energized electromagnet inn at least one north and south pole pair, and said field pole means is connected to the coils of said motor armature means through the brushless power unit in series, shunt, and compound mode for DC operation and in series mode for AC operation.

9. The brushless rotating electrical machine as claimed in claim 6 wherein said semiconductor switching devices are controlled such that each coil of said motor armature means is energized only during a period when it is magnetically coupled by flux under said field pole means and is de-energized when it is in the interpolar region thereby minimizing armature action and eliminating the need for interpoles and compensating windings, and after each coil of said motor armature means passes through the magnetic neutral axis between the two opposite magnetic poles of reverse polarity on said field pole means, at which point the direction of the current in each coil of the motor armature means is reversed to continue the torque in the same direction.

10. The brushless rotating electrical machine as claimed in claim 6 wherein said semiconductors switching devices are controlled by pulse width modulation signals from said means for generating commutation signals, and when pulse width modulation control is not intended, conventional method of using resistor in series with the motor armature means or the motor field member means is used to control the speed of the machine.

11. The brushless rotating electrical machine as claimed in claim 6 further comprises:

a polyphase AC winding means including a plurality of coils capable of generating a rotating magnetic field, said polyphase AC winding means is located on said motor field member means;

a first brushless power unit means comprising a plurality of said brushless power units connected to said polyphase AC winding means, said first brushless power unit means is located on said motor armature means;

said plurality of semiconductor switching devices, located on the timing and control unit, commutates the current in the coils of said polyphase AC winding means, thereby generating slip frequency power output in the coils of said polyphase AC winding means; and

said motor field member means is supplied with voltage at supply frequency whereby a motor action occurs by interaction between the motor armature means and the motor field member means.

12. The brushless rotating electrical machine as claimed in claim 6 further comprises:

a first polyphase AC winding means, located on said motor field member means;

a first brushless power unit means supplying AC power to a second polyphase AC winding means, located on said motor armature means and is supplied with voltage at supply frequency;

a secondary polyphase AC winding means, located on said motor armature means, and coupled to said second polyphase AC winding means;

a second brushless power unit means connected to the secondary polyphase AC winding means;

said plurality of semiconductor switching devices commutates the current in said second polyphase AC winding means thereby generating slip frequency power output in said secondary polyphase AC winding means; and

said secondary polyphase AC winding means is further connected to the second brushless power unit means whereby a slip frequency voltage is induced at a stationary member of the second brushless power unit means which is then injected in the first polyphase AC winding means, and when connected in a schrage type motor configuration, speed and power factor can be controlled.

13. The brushless rotating electrical machine as claimed in claim 6 wherein said motor armature means comprises disc type rotor having radial slots to carry current in the coils of said motor armature means, and said motor field member means produces flux along the axis of the machine shaft to link the coils of said motor armature means,

14. The brushless rotating electrical machine as claimed in claim 6 wherein said motor armature means comprises disc type rotor with radial slots to carry DC excitation.