Frequency Converter

A frequency converter, comprising:

• a first phase connection for the connection of a first phase of a three-phase AC grid voltage, a second phase connection for the connection of a second phase of the three-phase AC grid voltage, and a third phase connection for the connection of a third phase of the three-phase AC grid voltage;
• a three-phase bidirectional power converter that is electrically connected to the first phase connection, the second phase connection and the third phase connection and that is designed to generate a DC voltage from the three-phase AC grid voltage, wherein the bidirectional power converter has three bridge branches, wherein a respective one of the three bridge branches comprises:
• a first semiconductor switching device having a control input and a second semiconductor switching device having a control input, wherein the first semiconductor switching device and the second semiconductor switching device are connected in series between a first conductor, which carries a positive intermediate circuit potential, and a second conductor, which carries a negative intermediate circuit potential, and a connection node of the first semiconductor switching device and of the second semiconductor switching device is electrically connected to an associated phase connection of the phase connections;
• and
• a gate driver that is designed to generate a first drive signal and a second drive signal based on a potential of the associated phase connection of the phase connections, wherein the control input of the first semiconductor switching device has the first drive signal applied to it and the control input of the second semiconductor switching device has the second drive signal applied to it;
• and
• a monitoring unit that is designed to detect a failure of at least one mains phase of the three-phase AC grid voltage,
• wherein
• the monitoring unit has the respective first drive signals applied to it and is designed to detect the failure of the at least one mains phase of the three-phase AC grid voltage based on a temporal profile of the respective first drive signals.