| 摘要 |
PROBLEM TO BE SOLVED: To automatically disconnect the primary of a transformer from a power source when a load is not connected to its secondary and, when the load is connected, detecting this to connect the primary to the power source. SOLUTION: An auxiliary winding 6 is formed on a transformer to detect the change of the saturation magnetization of a transformer core. When a load does not exist it operates an interruption circuit connected between a power source and primary to cut off. After the cut off, a current flows in the primary winding 5 from an inquiry circuit 30 for a very short time to determine in the same operation whether the load exists or not, and it resets the interruption circuit from the cut off condition when the load exists. |
