Switching module

A switching module comprising:

• at least one combination of two input terminals, to which AC voltage of a set cycle that is set in advance is applied, and two output terminals, which are connected to a power conversion circuit;
• a combination of the two input terminals and the two output terminals selected from the at least one combination of the two input terminals and the two output terminals includes:
• a first bidirectional switch connected in series between one of the two input terminals and one of the two output terminals;
• a second bidirectional switch connected in series between another one of the two input terminals and another one of the two output terminals;
• an ammeter to detect a current value of a current flowing between the one of the two input terminals and the first bidirectional switch;
• and
• a determiner to determine whether the first bidirectional switch has a short circuit failure, wherein the determiner opens the first bidirectional switch and closes the second bidirectional switch from a first time point over a first testing period, which has a length of less than or equal to one-half of the set cycle, to obtain the current value and determine that the first bidirectional switch has a short circuit failure when the obtained current value is greater than or equal to a preset first current threshold value, and when determining from the current value, which is obtained from the first time to when the first testing period elapses, that the first bidirectional switch is functioning normally, the determiner opens the first bidirectional switch and closes the second bidirectional switch from a second time point, which is after a period corresponding to at least one cycle of the set cycle elapses from the first time point and when a polarity of the AC voltage differs from that at the first time point, to obtain the current value and determine that the first bidirectional switch has a short circuit failure when the obtained current value is greater than or equal to the first current threshold value.

A switching module comprising:

• at least one combination of two input terminals, to which AC voltage of a set cycle that is set in advance is applied, and two output terminals, which are connected to a power conversion circuit;
• a combination of the two input terminals and the two output terminals selected from the at least one combination of the two input terminals and the two output terminals includes:
• a first bidirectional switch connected in series between one of the two input terminals and one of the two output terminals;
• a second bidirectional switch connected in series between another one of the two input terminals and another one of the two output terminals;
• a first voltmeter to detect a first voltage value corresponding to an electric potential difference of an electric potential between the one of the two input terminals and the first bidirectional switch and an electric potential between the another one of the two input terminals and the second bidirectional switch;
• a second voltmeter to detect a second voltage value corresponding to an electric potential difference of an electric potential between the one of the two output terminals and the first bidirectional switch and an electric potential between the another one of the two output terminals and the second bidirectional switch;
• and
• a determiner to determine whether the first bidirectional switch has a short circuit failure;
• wherein
• the determiner executes a first determination process that opens the first bidirectional switch and closes the second bidirectional switch from a first time point over a first testing period, which has a length of less than or equal to one-half of the set cycle, obtains the first voltage value and the second voltage value to repetitively determine whether a first differential value of the first voltage value and the second voltage value is less than or equal to a preset first voltage threshold value, and determines that the first bidirectional switch has a short circuit failure when successively determining that the first differential value is less than or equal to the first voltage threshold value for a number of times that is greater than or equal to a preset first number threshold value, and the determiner executes a second determination process that opens the first bidirectional switch and closes the second bidirectional switch from a second time point, which is after a period corresponding to at least one cycle of the set cycle elapses from the first time point and when a polarity of the AC voltage differs from that at the first time point, over a second testing period, which has a length of less than or equal to one-half of the set cycle, obtains the first voltage value and the second voltage value to repetitively determine whether a second differential value of the first voltage value and the second voltage value is less than or equal to the first voltage threshold value, and determines that the first bidirectional switch has a short circuit failure when successively determining that the second differential value is less than or equal to the first voltage threshold value for a number of times that is greater than or equal to the first number threshold value.