Fault protection for GTO voltage-source inverters
AssigneeGeneral Electric Company
InventorWilliam McMurray
Life of this patent
Estimating the term…
Abstract
A crowbar circuit is provided in an inverter for diverting overcurrents from the inverter switches. The crowbar circuit includes a crowbar switch and a crowbar winding which is magnetically coupled with the inverter snubber reactors. The size and the coupling of the crowbar winding are chosen so as to reduce or make negative the di/dt of the snubber reactors when the crowbar switch is turned on.
Claims19
A phase leg of an inverter, comprising:
- a plurality of series-connected controlled turn-off phase leg switches for coupling to a dc power supply in a series aiding direction and providing an ac output;
- inductive snubber means for limiting di/dt during turn-on of said phase leg switches connected in series with said phase leg switches and having an inductance L.sub.1 ;
- a crowbar inductance having an inductance L.sub.2 and magnetically coupled to said inductive snubber means with a mutual inductance M;
- and
- a unidirectionally-conducting crowbar switch connected in said direction in series with said crowbar inductance, said crowbar switch adapted to be turned on upon the onset of an overcurrent fault so as to thereupon conduct crowbar inductance current;
- said inductances L.sub.1, L.sub.2 and M cooperatively reducing the rate of current increase in said phase leg switches when said crowbar switch is turned on.
A voltage-source inverter comprising:
- a plurality of parallel-connected phase legs, each leg including a plurality of series-connected phase leg switches for coupling to a dc power supply and inductive snubber means for limiting di/dt during turn-on of said phase leg switches connected in series with said phase leg switches and having an inductance L.sub.1, and providing an ac output;
- a plurality of crowbar inductances, each having an inductance L.sub.2 and magnetically coupled, respectively, to each of said inductive snubber means, respectively, with a mutual inductance M, respectively,;
- and
- a crowbar switch coupled to said crowbar inductances for permitting current flow in said crowbar inductances upon the onset of an over-current fault;
- said inductances L.sub.1, L.sub.2 and M cooperatively reducing the rate of current increase in each respective leg when said crowbar switch is turned on.
A method for providing overload protection in a voltage-source inverter, said inverter including at least one phase leg having a plurality of series-connected phase leg switches for coupling to a dc power supply of voltage e.sub.1 and an inductive snubber means for limiting di/dt during turn on of said phase leg switches connected in series with said phase leg switches and having an inductance L.sub.1, said inverter further including a crowbar inductance having an inductance L.sub.2 magnetically coupled to said inductive snubber means with a mutual inductance M, and a crowbar switch connected in series with said crowbar inductance, said crowbar inductance receiving a voltage e.sub.2 when said crowbar switch is turned on, said method comprising the steps of:
- (1) detecting an overcurrent fault;
- (2) turning on said crowbar switch so that at least a portion of said overcurrent flows in said crowbar inductance;
- and
- (3) turning off said phase leg switches by reducing current in said inductive snubber means to substantially zero by virtue of said inductances L.sub.1, L.sub.2 and M satisfying the relationship L.sub.2 (e.sub.1 /e.sub.2)<M<L.sub.2 (e.sub.2 /e.sub.1).
A method for providing overload protection in a voltage-source inverter, said inverter including at least one phase leg having a plurality of series-connected phase leg switches for coupling to a dc power supply of voltage e.sub.1 and an inductive snubber means for limiting di/dt during turn on of said phase leg switches connected in series with said phase leg switches and having an inductance L.sub.1, said inverter further including a crowbar inductance having an inductance L.sub.2 magnetically coupled to said inductive snubber means with a mutal inductance M, and a crowbar switch connected in series with said crowbar inductance, said crowbar inductance receiving a voltage e.sub.2 when said crowbar switch is turned on, said method comprising the steps of:
- (1) detecting an overcurrent fault;
- (2) turning on said crowbar switch so as to divert from said inductive snubber means through said crowbar inductance at least a portion of said overcurrent;
- and
- (3) limiting current in said phase leg switches and in said inductive snubber means by virtue of said inductances L.sub.1, L.sub.2 and M satisfying the relationship M<L.sub.1 (e.sub.2 /e.sub.1).
Dependencies are inferred from the claim text.