Resistance welder controller

A resistance welder controller comprising:

• a control unit that controls a welding current flowing through an inverter transformer;
• a current detection unit that detects the welding current flowing through the inverter transformer;
• a usage rate calculation unit configured to active:
• a usage rate measurement mode in which an energizing time and a point time interval of the welding current that has been detected for each point is measured and a usage rate of the inverter transformer using the energizing time and point interval time is calculated;
• and
• an average usage rate measurement mode in which the energizing time and the point time interval of the welding current that has been detected for each point or for a fixed time is measured, an average energizing time or an average point time interval for each of a plurality of points or for the fixed time is calculated, and the usage rate of the inverter transformer is calculated using the average energizing time or the average point time interval that have been calculate;
• a storage unit that stores an equivalent current curve indicating a relationship between a current value of the welding current and the usage rate of the inverter transformer when the inverter transformer is operated at a rated capacity;
• and
• a determination unit that determines whether a relationship between the current value of the detected welding current and the calculated usage rate of the inverter transformer in either of the usage rate measurement mode or the average usage rate measurement mode exceeds the rated capacity of the inverter transformer based on the equivalent current curve, continues an operation of the control unit when the relationship between the current value of the detected welding current and the calculated usage rate of the inverter transformer does not exceed the rated capacity of the inverter transformer, and stops the operation of the control unit when the relationship between the current value of the detected welding current and the calculated usage rate of the inverter transformer exceeds the rated capacity of the inverter transformer.