Abstract An auxiliary winding is located adjacent the main winding of the superconductive coil, the flux relationship between the flux generated by the main winding and by the auxiliary winding being a predetermined factor, for example unity or a whole number factor of proportionality; upon transition from superconductive to resistant state of any portion of the main winding, the IR drop in the superconductive winding will appear as a signal between the superconductive winding and the auxiliary winding, irrespective of inductive voltages. This signal is compared with a voltage drop across a resistance in the supply of the main winding to obtain an alarm which can be used to disconnect the superconductive coil from a supply.
System according to claim 1, wherein the means deriving a current signal comprises a resistance (11) in series circuit with the superconductive coil (2), said signal being the IR drop across said resistance.
Claim 2
Dependent Claim
17 words
System according to claim 1, including a fixed dissipating resistance (9) connected across said superconductive coil (2).
Claim 3
Dependent Claim
82 words
System according to claim 1, wherein said predetermined relationship is a predetermined factor, said auxiliary winding having a lesser number of turns than said coil, said auxiliary winding being located so that the flux cut of said auxiliary winding is equal to the flux cut in said coil; and an amplifier is provided having a gain which is the reciprocal of said factor, said amplifier being connected to have said first signal applied thereto and having its output connected to said comparator.
Claim 4
Dependent Claim
74 words
System according to claim 1, wherein said predetermined relationship is a predetermined factor, said auxiliary winding being located so that the flux cutting said auxiliary winding differs from said total magnetic flux of said superconductive coil by a second factor; and an amplifier is provided having a gain which is the reciprocal of said second predetermined factor and the reciprocal of the ratio of numbers of turns of said auxiliary winding and said coil.