Abstract
Quench detection is an essential technique to protect superconducting coils from excessive ohm-generated heating after quenching. We previously proposed an electric quench detection method based on detecting active power, which is less susceptive to electromagnetic noise. However, this method is vulnerable to high voltage because it requires a central voltage tap to detect the active power (or cancel the reactive power). In other words, a lead-wire from the tap may short circuit as the result of high voltage. In this paper, we present an electric quench detection method without a central voltage tap. In this method, an inductive voltage detection coil is used instead of a central voltage tap. The inductive voltage measured by the inductive voltage detection coil and that of the superconducting coil are in phase, therefore the inductive voltage (or reactive power) of the superconducting coil can be canceled by offsetting the inductive voltages. Like the previous method, this method can also detect quenching regardless of noise superposition. Through the quench detection tests for a Bi-2223/Ag HTS coil, we show the feasibility of the proposed method for detecting the quench of a large AC superconducting coil.
