The quench behavior of conduction-cooled Y Ba2Cu 3O7-δ (YBCO) coated conductor pancake coils is reported. Two coils, one stabilized with copper and one with brass, are wound with 25m of conductor and instrumented with a heater and a large number of voltage taps and thermocouples. The critical current, minimum quench energy (MQE) and two-dimensional normal zone propagation velocity (NZPV) are measured as a function of I/Ic, where I is the transport current and I c is the critical current. Although the non-uniform temperature and self-field distributions within the coils result in a non-uniform Ic, the heater is able to induce quenches with energies above the MQE and both longitudinal and transverse propagation velocities are measured. In both coils, the longitudinal NZPV (10-40mms- 1) is about one order of magnitude larger than the transverse NZPV (1-2mms- 1). Moreover, a comparison between the Cu-stabilized coil and a short, straight Cu-stabilized sample shows that the one-dimensional longitudinal propagation in the short sample is significantly faster than the longitudinal propagation in the coil. This is due to transverse heat conduction (transverse propagation) which reduces the temperature gradients in the coil but also slows down the longitudinal propagation. Thus, designing a quench detection system based upon data from one-dimensional experiments may result in an unintended level of risk.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Condensed Matter Physics
- Metals and Alloys
- Materials Chemistry
- Electrical and Electronic Engineering