A controllable power take-off for magnetohydrodynamic generators

Electrical power must be extracted from a magneto-hydrodynamic (MHD) generator by a power take-off (PTO) system that consolidates the current from the MHD channel's electrodes into a single load current.

In the conventional PTO system constructed from diodes and resistors, desired electrode currents cannot be maintained when generator conditions vary. In addition, significant power is dissipated in the resistors used. To overcome these problems, a controllable PTO circuit has been proposed using switching transistors to control the electrode currents.

To study the behavior of the switching PTO, a representative model using a proportional-integral con-troller was simulated and its operation examined. Simulation results verify that the controlled switching method can force the average electrode currents to their desired values as generator parameters vary. It is also found that there is a reduced power loss with the switching PTO circuit. These results indicate that it would be advantageous to replace the conventional PTO method by the controlled switching transistor system.