Abstract: A filter short circuit is detected when the primary voltage of the high-voltage transformer drops below a specified minimum value and does not rise above the specified minimum value during a specified delay period and a filter current is greater than a specified minimum current. No current is drawn from the external current supply for a variable time delay when a filter short circuit is detected. A filter short circuit count is incremented when a filter short circuit is detected. When the count exceeds a specified, variable limit within a specified, variable time span, the indirect converter is disconnected.

Abstract: A voltage supply for an electric filter is disclosed. The supply comprises a high-voltage rectifier, a pulsed voltage circuit including a resonant circuit and a parallel circuit of a thyristor and a diode which controls resonance in the resonant circuit. The thyristor is fired to trigger the resonant circuit and generate an oscillation which is delivered to the filter as a pulsed voltage. In order to prevent damage to the thyristor, it is fired whenever the duration of the current flowing through the diode is shorter than the thyristor recovery time.

Abstract: An electrostatic precipitator is fed high voltage pulses by a pulse generating circuit including a high voltage transformer and a first thyristor switch connected in series with a primary winding of the transformer. Magnetic saturation of the core of the high voltage transformer is prevented by recurrently short circuiting the primary winding of the transformer by means of a second thyristor switch connected in parallel to the primary winding. The second thyristor switch is closed for a period of time extending from a first instant following a high voltage pulse crest to a second instant at or before the start of a pulse generating cycle subsequent to the pulse crest.

Abstract: An embodiment of the present invention provides an excitation arrangement suitable for use in producing a pulse-shaped field of substantially constant intensity. To start-up the current at the beginning of a pulse, a coil (1) is fed with a high voltage (line 3) via an ignitable and blockable power semiconductor (7). For the duration of the pulse, switch-over is then effected to the supply of a lower voltage (line 4) by means of a power transistor (31) controllable to a constant current. Free-running diodes are used to decay the current. One coil end (2) is preferably connected via an FET (7) which is controllable to a constant voltage, to the high voltage; via an FET (30), which is likewise controllable to a constant voltage, to the lower-voltage (4); and via a controllable FET (52) to a reference line (6). Corresponding FET's (50, 51, 31) are provided at the other coil end (5).

Abstract: A method for operating an electrostatic precipitator with a DC voltage and superimposed pulses or superimposed AC voltage in which individual parameters such as amplitudes, pulse repetition frequency, pulse width, etc. are iteratively and continuously varied in such a manner that the sum of the pulse and the DC voltage power approaches a minimum. A computer which calculates, from the dust load and the absorbed electric energies of the filter, control commands for the DC and pulse voltage source is used for this purpose.

Abstract: A protection arrangement for an inverter having fuses connected in series with its d-c inputs is disclosed. In particular, in one form of the arrangement, an electronic voltage monitoring device is provided for monitoring the input d-c voltage to the inverter at the connection points of the inverter inputs and the fuses. If the voltage monitored by the monitoring device falls below a predetermined level, the monitoring device delivers a protection signal to the control unit of the inverter directing the latter to release firing pulses for extinguishing the valves in the valves branches of the inverter.In another form of the arrangement, the voltage monitoring device monitors the voltage across each of the fuses at the d-c inputs of the inverter, and, if a monitored voltage exceeds a predetermined value, delivers a protection signal to the control unit of the inverter.