Abstract: An inverter type drive unit for feeding AC electric power of variable parameters to an electric motor has an electronic control section, and a power converting and output section which includes one or more identical power modules, each forming a complete 3-phase output stage. The power modules are arranged side-by-side in a multiplying direction and are clamped by retaining devices to a cooling structure. The power modules are connected in parallel to DC input terminals and to AC output terminals via conductive sheets which are insulated from each other. The DC connected conductive sheets cover substantially the entire physical surface area covered by the power modules so as to accomplish an even, simultaneous and low impedance DC current supply to all power modules.

Abstract: This invention propose a way of controlling the flux density in a current transformer to keep the transformer core saturated between two consecutive measurements in a sampling measurement system. Saturation disables transformation of primary to secondary current, and thereby disables losses in the secondary circuit during this time. Both AC and DC currents are possible to measure. The use of saturation of the transformer core also permits the core to be designed physically very small. In order to get effective and accurate low power consuming measurements, both the magnetic fields originating from primary current flowing in the primary winding and external magnetic fields must be symmetrically physically spread in the transformer core. This greatly limits the possible physical arrangement of the primary winding.