Abstract: An electrical short-circuit monitoring arrangement for a three-phase motor, including its supply lines, whose speed is controlled by a constant-current d.c.-link converter. The harmonic ripple voltage superimposed on the motor voltage generated as a consequence of the commutation by the constant-current d.c.-link converter at the output of the converter is determined, filtered, and supplied to a phase-monitoring unit, which when dropping below a selected amplitude variable of the harmonic voltage of at least one phase, triggers the switching module whose switching mechanism activates a disconnect switch to interrupt the motor circuit upon occurrence of a switchoff signal.

Abstract: A circuit arrangement is disclosed for supplying an electric machine from a d-c voltage source. The circuit arrangement comprises a self-commutating inverter having valve branches that can be fired and extinguished and d-c voltage inputs to which electronic switching members are connected. In accordance with the invention, a capacitor is connected to the output of the inverter via a rectifier, and the d-c voltage outputs of the latter are connected via current paths with the poles of the d-c voltage source. To obtain at least partial recovery of the energy stored in the capacitor ohmic resistors are arranged in the current paths. Complete energy recovery is, in turn, realized by arranging controlled electronic valves in the current paths.

Abstract: A method and apparatus for operating a rotating field machine, which is controlled by an inverter of the type which provides only a predetermined limited number of discrete positions of the stator current vector, in such a manner so that when it is desired to position the machine between two of the discrete vector positions, the discrete positions on each side of the desired vector position are alternatively energized resulting in an average position which is the desired vector position. For operation in a system where the vector can only rotate in one direction apparatus is disclosed which permits the alternate energization to occur by moving the vector at the maximum possible speed over the portion of rotation which is outside an area surrounding the desired position and moving it more slowly while inside this area.

Abstract: A commutation circuit for a converter is disclosed. The circuit comprises an intermediate DC link which is coupled at one end to the converter and which includes a smoothing choke. A DC controller is coupled to the other end of the DC link and includes a controlled main valve and a quenching arrangement which is shunted across the main valve and comprises a quenching capacitor in series with controlled quenching valve. In accord with the invention the aforesaid smoothing choke and quenching capacitor serve as the respective quenching capacitor and quenching choke for sum quenching of the controlled valves of the converter.

Abstract: In a d-c control circuit of a type comprising a controllable main valve, a commutation capacitor, a commutation choke and controllable commutation valve, a flyback valve arranged antiparallel to the main valve and a bypass valve, provision is made for connecting between the d-c voltage source and the main valve the primary winding of a transformer whose secondary winding, in series with a blocking diode, is connected parallel to the d-c voltage source. Additionally, provision is also made for connecting the commutation valve antiparallel to the bypass valve. With the d-c control circuit so configured, the load current can now flow in both directions.