Method and apparatus for shutting down an inverter

Claim 3

The method according to claim 1 and further comprising, upon a shutdown command, changing the control voltage for the control set in a direction toward the smallest possible output voltage of the inverter.

Claim 4

A circuit for shutting down an inverter with controlled main valves, the control terminals of which are connected via an enabling unit to a control set having as an input a control voltage determining the firing angle of the firing pulses comprising: (a) the enabling unit including at its input a group of first inhibit gates, one for each main valve, the inputs of which are addressed by the firing signals for the main valves and in common by a change blocking signal, a bistable multivibrator for each two gates having the outputs of said gates as inputs and a group of second inhibit gates, one for each main valve, at its output having as inputs the outputs of said bistable multivibrators and, as a common input, a blocking command; (b) means for monitoring the output signals of said bistable multivibrators to indicate the valve state of the main valves and to generate a zero voltage signal when firing signals for the main valves connected to a d-c bus of the inverter are present simultaneously; (c) ANDing means having as inputs a shutdown command and the zero voltage signal and providing as an output blocking signal for said first inhibit gates; and (d) delay means addressed by said change blocking signal having as an output said blocking command for for said second inhibit gates.

Claim 5

A circuit for shutting down an inverter with controlled main valves, the control terminals of which are connected via an enabling unit to a control set having as an input a control voltage determining the firing angle of the firing pulses comprising: (a) the enabling unit including at its input a group of first inhibit gates, one for each main valve, the inputs of which are addressed by the firing signals for the main valves and in common by a change blocking signal, a bistable multivibrator for each two gates having the outputs of said gates as inputs and a group of second inhibit gates, one for each main valve, at its output having as inputs the outputs of said bistable multivibrators and, as a common input, a blocking command; (b) means for monitoring the output signals of said bistable multivibrators to indicate the valve state of the main valves and to generate a zero voltage signal when firing signals for the main valves connected to a d-c bus of the inverter are present simultaneously; (c) ANDing means having as inputs a shutdown command and the zero voltage signal and providing as an output blocking signal for said first inhibit gates; and (d) delay means addressed by said change blocking signal having as an output said blocking command for for said second inhibit gates.

Claim 6

A circuit according to claim 3 and further including means for switching the control voltage for the control set to a value for the minimum output voltage of the inverter upon a shutdown command.