Balanced 20-kA DC Distributor for Magnetized Taylor Couette Systems, Utilizing Thermostatic Controlled Water Valves With CO2Adsorption Charge Sensors as Current Controller

Abstract

A quasi-coaxial system consisting of a central current carrying copper rod and five symmetric return paths takes up to 20 kA. The installation provides a homogeneous magnetic field $\mathbf {B_{\varphi }}$ to a Taylor–Couette flow. One challenging part of the system is the design of the current distributor, which is supposed to divide the return current into several equally weighted lines. The individual components like the copper rods as well as all electrical contacts provide a characteristic resistance, each in the same magnitude of several $ {\mu }\Omega $ . By initial installation this will support an imbalance in the current distribution affecting the symmetry of the magnetic field. So the adjustment of current distribution becomes mandatory to ensure maximum field homogeneity. Controlling the outflow temperature of the required water cooling offers an indirect access to set the current by thermostatically operated valves with CO2 adsorption charge in conjunction with the temperature dependent branch resistance. A numerical investigation proves that a stable current distribution can be achieved by a couple of paralleled thermal controlled heater valves with proportional characteristics. Finally, recent ironless Hall-effect current sensors help to calibrate the system so that the current homogeneity differs less than 1% from optimal state in a wide range of currents.