﻿Stability, i.e. the possibility of self-recovery of a superconductor after a quench, is one of the most important features of technical superconductors. The stability of a superconductor is determined quantitatively by some limiting parameters, called indicators or parameters of stability, which delimit the region of safe (stable) operation of the superconductor. The parameters of stability are used in the design and operation of superconducting devices.
In the introductory part of the work, after a short description of the structure and properties of the technical superconductors, there are characterized the most often used stability parameters as well as the methods of their determination.
The essential part of the work starts with the derivation of a heat conduction equation of a new type which can be used for the description of quick-changing heat processes in the superconductors. This equation takes into account the finite velocity of heat flux propagation and the relaxation of heat source capacity.
Further on, there are successively discussed elaborated by the author analytical methods for calculation of the stability parameters, first of all the critical energy of the conductor which is the most frequently used one.
The presented method for calculation of the minimum propagating current allows for the full boiling characteristic of the coolant and permits any dependence of the heat conductivity of the conductor on temperature.
The proposed general analytical method for calculation of the critical energy as equal to the enthalpy increase in the normal zone considers both quasi stationary minimum propagating zones and transient propagating zones. This method takes into account nucleate and film boiling of the coolant.
The analytical method for calculation of the critical energy of thermally insulated superconductors takes into consideration transient heat transfer in the conductor, temperature dependent conductor properties as well as the finite duration and finite length of heat disturbances.
The analytical method for calculation of the critical energy of the conductor remaining in the intimate contact with the coolant allows for transient heat transfer in the conductor and coolant, and the finite duration and finite length of heat disturbances.
In the latter part of the work there is discussed a transient numerical model of the normal zone taking account of the precise temperature dependencies of the conductor thermal conductivity and heat capacity, the current sharing region, transient heat transfer to the coolant as well as the non-linearity of the steady boiling characteristic of the coolant.
Using the elaborated analytical and numerical methods there is also carried out the investigation of influence of basic variables characterizing the superconductor and its operating conditions on the value of stability parameters. On the ground of this investigation a number of general conclusions are drawn. The comparison of the calculated values of the stability parameters with experimental and calculated ones taken from literature is made as well. In most cases the agreement is good.