Three Phase brushless DC motor

Claim 2

A three phase brushless DC motor for precision servo applications, comprising, a stationary armature having three sets of windings symmetrically positioned thereon; a two pole permanent magnet rotor mounted for rotation relative to said armature; photoelectric self commutation means including a square wave generation circuit connected to said sets of windings, half cone reflector means axially mounted to rotate with said rotor for reflecting light projected thereon by a source, a light source for projecting light on said half cone reflector means, three photodetectors connected to said ciRcuit positioned symmetrically about said rotor so as to receive the reflected light, said reflector means and said photodetectors being relatively positioned and said reflector means having a 180* arc of reflection to produce signals in said sets of windings without odd harmonic distortion.

Claim 3

A three phase brushless DC motor according to claim 1 wherein: said photodetectors comprise phototransistors; and said light source comprises a light emitting diode.

Claim 4

A three phase brushless DC motor for precision servo applications, comprising, a stationary armature having three sets of windings symmetrically positioned thereon; a two pole permanent magnet rotor mounted for rotation relative to said armature; photoelectric self commutation means including a square wave generation circuit connected to said sets of windings, reflector means comprising a planar surface inclined with respect to the axis of said rotor axially mounted to rotate with said rotor for reflecting light projected thereon by a source, a circular light source for projecting light on said planar surface reflector means, three photodetectors connected to said circuit positioned symmetrically about said rotor so as to receive the reflected light, a shield mounted about said circular light source to prevent spurious light from being received by said photodetectors, said reflector means and said photodetectors being relatively positioned and said reflector means having a 180* arc of reflection to produce signals in said sets of windings without odd harmonic distortion.

Claim 5

A three phase brushless DC motor for precision servo applications, comprising, a stationary armature having three sets of windings symmetrically positioned thereon; a two pole permanent magnet rotor mounted for rotation relative to said armature; photoelectric self commutation means including a square wave generation circuit connected to said sets of windings, reflector means comprising a planar surface inclined with respect to the axis of said rotor axially mounted to rotate with said rotor for reflecting light projected thereon by a source, a circular light source for projecting light on said planar surface reflector means, three photodetectors connected to said circuit positioned symmetrically about said rotor so as to receive the reflected light, a shield mounted about said circular light source to prevent spurious light from being received by said photodetectors, said reflector means and said photodetectors being relatively positioned and said reflector means having a 180* arc of reflection to produce signals in said sets of windings without odd harmonic distortion.

Claim 6

A three phase brushless DC motor for precision servo applications, comprising, a stationary armature having three sets of windings symmetrically positioned thereon; a two pole permanent magnet rotor mounted for rotation relative to said armature; photoelectric self commutation means including a square wave generation circuit connected to said sets of windings, reflector means comprising a cylindrical reflector mounted axially with respect to said rotor having three reflective strips displaced from one another in the axial direction each describing a 180* arc, three light sources respectively positioned adjacent said three reflector strips, three photodetectors positioned so as to receive, respectively, light reflected from each light source by its adjacent strip, said reflector strips, said light sources and said photodetectors being relatively positioned to produce signals in said sets of windings without odd harmonic distortion.

Claim 7

A three phase brushless DC motor for precision servo applications, comprising, a stationary armature having three sets of windings symmetrically positioned thereon; a two pole permanent magnet rotor mounted for rotation relative to said armature; photoelectric self commutation means including a square wave generation circuit connected to said sets of windings, reflector means comprising a cylindrical reflector mounted axially with respect to said rotor having three reflective strips displaced from one another in the axial direction each describing a 180* arc, three light sources respectively positioned adjacent said three reflector strips, three photodetectors positioned so as to receive, respectively, light reflected from each light source by its adjacent strip, said reflector strips, said light sources and said photodetectors being relatively positioned to produce signals in said sets of windings without odd harmonic distortion.