Abstract: Circuitry for, and method of operating, an intermediate-link converter of the type wherein two controlled antiparallel-connected converters are connected via an intermediate link having an impressed voltage to an inverter having a plurality of addressable switches in a three-phase bridge circuit. The polarity of the intermediate-link current is interrogated 30.degree. after every change of the addressing combination of the switches of the inverter. If the interrogated polarity of the intermediate-link voltage is larger than a desired value by a predetermined amount, the converter which is arranged in the feeding-in direction is switched off and the other converter, which is arranged in the feedback direction is switched on. In this manner, a load connected to the inverter can feedback energy into a supply network via the intermediate link and a converter operating as an inverter.

Abstract: Method and apparatus for producing a speed-proportional signal from first and second transmitter voltages which are produced by an incremental position generator and shifted 90.degree. with respect to each other in directions which correspond to the direction of rotation of the incremental position generator. An adder and a subtractor are provided for respectively producing a sum signal corresponding to an addition of the transmitter voltages, and a difference signal corresponding to the difference between the transmitter voltages. The sum and difference signals are each differentiated over ranges which correspond to .+-.45.degree. about their respective zero crossing. The differentiated signals are rectified in a controlled manner responsive to the phase of the first and second transmitter voltages. In this manner, a speed-proportional voltage is produced having a polarity which corresponds to the direction of rotation of the position transmitter.

Abstract: An apparatus and method for increasing the maximum speed of rotation of a synchronous machine having constant excitation field strength is disclosed. The synchronous machine is preceded by a converter, which has an adjusted current reference value as an input. The adjusted current reference value comprises an active-current reference value and a reactive-current reference value. For actual speeds n.sub.ist, the absolute value .vertline.n.sub.ist .vertline. of which is above a predetermined value n.sub.o, the amplitude of the active-current reference value is limited to a value which is inversely proportional to the factor .vertline.n.sub.ist .vertline./n.sub.o. The value n.sub.o is a predetermined speed at which the sum of the magnet wheel voltage of the synchronous machine and the voltage drop in the stator winding is maximally equal to the largest possible output voltage of the converter. To obtain the adjusted current reference value, a reactive-current reference value shifted 90.degree.

Abstract: An arrangement for bridging brief network failures in intermediate-link converters converts the kinetic energy in load motors into electrical energy by reducing the frequency of the converter. Such a frequency reduction is performed in accordance with the value of a control deviation signal corresponding to the difference between desired and actual frequencies of operation of the converter. The control deviation signal is produced by the combination of a PI controller which is coupled at its output to an integrator circuit. The integrator circuit controls the frequency and voltage of the converter.

Abstract: A static frequency converter comprising an intermediate DC voltage link, a rectifier, and an inverter having main thyristors in a bridge circuit, across which bypass diodes in a bridge circuit are shunted antiparallel, has a quenching circuit shunted across each bridge arm which includes a quenching thyristor, a commutating capacitor, and a commutating choke. There is a common commutating capacitor for each two bridge arms having a common main terminal and an energy-removing device, assigned to each commutating choke, is connected after the potential change has occurred at the corresponding output terminal of the inverter, at the end of each commutation. Energy stored in the commutating choke is taken out by the energy-removing device and over-voltage of the commutating capacitors is prevented.

Abstract: In a cycloconverter including an intermediate d-c link, a controlled rectifier and a inverter having main thyristors in a bridge circuit with bypass diodes in a bridge connected antiparallel thereto, a quenching circuit including a quenching thyristor and a commutating capacitor is connected parallel to each bridge arm, there being provided for each two bridge circuits having a common main lead a common commutating capacitor and at least one common damping capacitor, the latter connected parallel to a bridge arm to reduce the current dependence of the commutation voltage present at the commutating capacitor.