Power mosfet bank

The power components used to drive the magnet current are an important part of the FFC power supply and can critically affect its performance. All together, these components constitute the power unit indicated in Fig. 12 as the Power Mosfet Bank. 

Fig. 16. Distribution of dissipated electrical power between the magnet and the Power Mosfet bank.

The primary circuit is closed and filled with a special cooling fluid which, driven by a high-capacity pump, cools the magnet and the Power Mosfet banks. The cooling fluid is a commercially available product (Galden ) whose physical characteristics had been optimized for cooling electric devices wherever it is not possible to use water. It is chemically almost inert, absolutely non-toxic, and electrically non-conductive. 

The power bank contains an adequate number (generally several tens) of linear solid-state power devices, such as transistors or power Mosfets. Because of the availability of modern power Mosfets that combine high performance with easy control, classical transistors are nowadays no longer used in applications of this type (in our case, we use channel-N and channel-P Mosfets for the positive and negative power supply sections, respectively). 

The positive section of the power banks shown in Fig. 14 uses 40 type-N power Mosfet devices which can drive currents of up to 400 A. The same banks mount also 4 type-P devices for the negative section. The number of devices in the negative section is much smaller since the negative side is subject to much smaller power requirements. All 44 devices are mounted, together with their electronic control boards, on four special liquid-cooled, copper heat sinks. These, thanks to the excellent thermal conductivity of copper, combined with a design which maximizes the contact area between the copper and the cooling liquid, makes it possible to reach the requested cooling efficiency. 

Currently, three basic high-frequency power amplifiers are in use the parallel connection of a bank of bipolar power transistors, the hybrid connection of parallel bipolar power transistors cascaded with metal oxide silicon field effect transistors (MOSFETs), and the bridge connection of MOSFETs. Each has unique properties and represents a stage in the evolution of ESUs. 

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