Electrical isolators

Claim 2

An electrical isolator comprising a transformer with primary and secondary circuits which are electrically isolated from each other, the transformer having a core, the primary circuit including a primary winding on the core and an impedance in series with the primary winding, the secondary circuit including a secondary winding on the core, a high gain amplifier having input and output terminals and connected to amplify voltage induced in the secondary winding and a feedback circuit connected and arranged to conduct a feedback current from the output terminal of the amplifier to produce magnetic flux in the core, which is opposed to flux produced by current in the primary winding, the feedback circuit comprising a feedback impedance and a further winding on the core which are connected in series with each other and connected between the output terminal of the amplifier and a common line.

Claim 3

Apparatus for converting into digital form signals comprising alternating carrier voltages from an angle sensing device, comprising three electrical isolators each comprising a transformer with primary and secondary circuits which are electrically isolated from each other, the transformer having a core, the primary circuit including a primary winding on the core and an impedance in series with the primary winding, the secondary circuit including a secondary winding on the core, a high gain amplifier having input and output terminals and connected to amplify voltage induced in the secondary winding and a feedback circuit connected and arranged to conduct feedback current from the output terminal of the amplifier to produce magnetic flux in the core which is opposed to flux produced by current in the primary winding, two of the isolators having their primary circuits arranged for receiving said alternating carrier voltage signals such that the output signals from their high gain amplifiers represent the sine and cosine of the angle sensed by the sensing device and the third said isolator being for receiving a reference alternating voltage carrier signal, and the apparatus further comprising a digital converter connected to receive said output signals of said two of the isolators for conversion into digital form and the output signal of said third isolator.

Claim 4

Apparatus for converting into digital form signals comprising alternating carrier voltages from an angle sensing device, comprising three electrical isolators each comprising a transformer with primary and secondary circuits which are electrically isolated from each other, the transformer having a core, the primary circuit including a primary winding on the core and an impedance in series with the primary winding, the secondary circuit including a secondary winding on the core, a high gain amplifier having input and output terminals and connected to amplify voltage induced in the secondary winding and a feedback circuit connected and arranged to conduct feedback current from the output terminal of the amplifier to produce magnetic flux in the core which is opposed to flux produced by current in the primary winding, two of the isolators having their primary circuits arranged for receiving said alternating carrier voltage signals such that the output signals from their high gain amplifiers represent the sine and cosine of the angle sensed by the sensing device and the third said isolator being for receiving a reference alternating voltage carrier signal, and the apparatus further comprising a digital converter connected to receive said output signals of said two of the isolators for conversion into digital form and the output signal of said third isolator.

Claim 5

Apparatus as claimed in claim 2 wherein the feedback circuit of said third isolator comprises a pair of back-to-back diodes connected between the output terminal of the high gain amplifier and an inverting input terminal thereof, one side of the secondary winding being connected also to the inverting input terminal and the other side being connected to a common line.

Claim 6

Apparatus for converting into digital form signals comprising alternating carrier voltages from an angle sensing device, comprising at least two electrical isolators each comprising a transformer with primary and secondary circuits which are electrically isolated from each other, the transformer having a core, the primary circuit including a primary winding on the core and an impedance in series with the primary winding, the secondary circuit including a secondary winding on the core, a high gain amplifier having input and output terminals and connected to amplify voltage induced in the secondary winding and a feedback circuit connected and arranged to conduct a feedback current from the output terminal of the amplifier to produce magnetic flux in the core which is opposed to flux produced by current in the primary winding, the feedback circuit comprising a feedback impedance and a further winding on the core which are connected in series with each other and connected between the output terminal of the amplifier and a common line, the isolators having their primary circuits arranged for receiving said alternating carrier voltage signals such that the output signals from their high gain amplifiers represent the sine and cosine of the angle sensed by the sensing device, and the apparatus further comprising a digital converter connected to receive said output signals for conversion into digital form.

Claim 7

Apparatus for converting into digital form signals comprising alternating carrier voltages from an angle sensing device, comprising at least two electrical isolators each comprising a transformer with primary and secondary circuits which are electrically isolated from each other, the transformer having a core, the primary circuit including a primary winding on the core and an impedance in series with the primary winding, the secondary circuit including a secondary winding on the core, a high gain amplifier having input and output terminals and connected to amplify voltage induced in the secondary winding and a feedback circuit connected and arranged to conduct a feedback current from the output terminal of the amplifier to produce magnetic flux in the core which is opposed to flux produced by current in the primary winding, the feedback circuit comprising a feedback impedance and a further winding on the core which are connected in series with each other and connected between the output terminal of the amplifier and a common line, the isolators having their primary circuits arranged for receiving said alternating carrier voltage signals such that the output signals from their high gain amplifiers represent the sine and cosine of the angle sensed by the sensing device, and the apparatus further comprising a digital converter connected to receive said output signals for conversion into digital form.