Capacitive welder and method for charging same
The capacitive welder includes a charging circuit, a welding transformer, a capacitor, a discharging switching element connected in parallel with a primary winding of the welding transformer and the capacitor that are connected in series, a bypass switching element connected in parallel with the primary winding, welding electrodes connected in parallel with a secondary winding of the welding transformer, and a control circuit for bringing the welding transformer into a reset allowing state by allowing a reset current to flow in the primary winding using the input power introduced through the charging circuit without supplying an ON signal to the bypass switching element, and then supplying the ON signal to the bypass switching element such that the capacitor is charged through the bypass switching element by the input power introduced through the charging circuit.
1. A capacitive welder comprising:
a charging circuit having a switching element;
a welding transformer having a primary winding and a secondary winding;
a capacitor to which an input electric power is introduced via the charging circuit;
a discharge switching element connected in parallel with the primary winding and the capacitor, the primary winding being connected in series to the capacitor;
a bypass switching element connected in parallel with the primary winding;
welding electrodes connected in parallel with the secondary winding of the welding transformer; and
a control circuit configured to bring the welding transformer into a reset allowing state by causing a reset current to flow in the primary winding using the input electric power introduced through the charging circuit without supplying an ON signal to the bypass switching element, and then supply the ON signal to the bypass switching element such that the capacitor is charged through the bypass switching element by the input electric power introduced through the charging circuit.
2. The capacitive welder according to claim 1 , wherein when the welding transformer is brought into the reset allowing state and the current starts flowing in the bypass switching element from the charging circuit, the control circuit controls the switching element in the charging circuit such that the bypass switching element is brought into a conduction state with a shorter on-time width than a maximum on-time width of when the current flows in the primary winding of the welding transformer before the switching element of the charging circuit is brought into the reset allowing state.
3. The capacitive welder according to claim 2 , wherein when a voltage of the capacitor that is charged with the current flowing through the primary winding becomes equal to or greater than a predetermined voltage for reset determination, when the current flowing through the primary winding becomes equal to or greater than a predetermined current for reset determination, when a differential voltage between the voltage of the capacitor and a previous voltage of the capacitor becomes equal to or greater than the predetermined voltage for reset determination, when a differential current between the current flowing through the primary winding and a previous current flowing through the primary winding is equal to or greater than the predetermined current for reset determination or when a predetermined time elapses since the current starts flowing through the primary winding, then the control circuit determines that the welding transformer is in the reset allowing state and supplies the on-signal to the bypass switching element.
4. The capacitive welder according to claim 1 , wherein when a voltage of the capacitor that is charged with the current flowing through the primary winding becomes equal to or greater than a predetermined voltage for reset determination, when the current flowing through the primary winding becomes equal to or greater than a predetermined current for reset determination, when a differential voltage between the voltage of the capacitor and a previous voltage of the capacitor becomes equal to or greater than the predetermined voltage for reset determination, when a differential current between the current flowing through the primary winding and a previous current flowing through the primary winding is equal to or greater than the predetermined current for reset determination or when a predetermined time elapses since the current starts flowing through the primary winding, then the control circuit determines that the welding transformer is in the reset allowing state and supplies the ON signal to the bypass switching element.
5. The capacitive welder according to claim 1 , wherein the discharge switching element includes a thyristor, and the bypass switching element includes a thyristor.
6. The capacitive welder according to claim 1 , wherein bias magnetism does not proceed in the welding transformer during the reset allowing state, even if a welding process is carried out continuously.
7. The capacitive welder according to claim 1 , wherein no current flows in the bypass switching element before the welding transformer is brought into the reset allowing state.
8. The capacitive welder according to claim 1 , wherein the primary winding has a larger impedance than the bypass switching element.
9. A method of charging a capacitive welder, the capacitive welder including:
a charging circuit having a switching element;
a welding transformer having a primary winding and a secondary winding;
a capacitor to which an input electric power is introduced via the charging circuit;
a discharge switching element connected in parallel with the primary winding and the capacitor, the primary winding being connected in series to the capacitor;
a bypass switching element connected in parallel with the primary winding; and
welding electrodes connected in parallel with the secondary winding of the welding transformer,
the method comprising:
bringing the welding transformer into a reset allowing state by causing a reset current to flow into the primary winding using the input electric power introduced through the charging circuit without supplying an ON signal to the bypass switching element; and then supplying the ON signal to the bypass switching element such that the capacitor is charged through the bypass switching element by the input electric power introduced through the charging circuit.
10. The method according to claim 9 , wherein when the welding transformer is brought into the reset allowing state and the current starts flowing in the bypass switching element from the charging circuit, the switching element in the charging circuit is controlled such that the bypass switching element is brought into a conduction state with a shorter on-time width than a maximum on-time width of when the current flows in the primary winding of the welding transformer before the switching element of the charging circuit is brought into the reset allowing state.
11. The method according to claim 10 , wherein when a voltage of the capacitor that is charged with the current flowing through the primary winding becomes equal to or greater than a predetermined voltage for reset determination, when the current flowing through the primary winding becomes equal to or greater than a predetermined current for reset determination, when a differential voltage between the voltage of the capacitor and a previous voltage of the capacitor becomes equal to or greater than the predetermined voltage for reset determination, when a differential current between the current flowing through the primary winding and a previous current flowing through the primary winding is equal to or greater than the predetermined current for reset determination or when a predetermined time elapses since the current starts flowing through the primary winding, then it is determined that the welding transformer is in the reset allowing state and the on-signal is supplied to the bypass switching element.
12. The method according to claim 9 , wherein when a voltage of the capacitor that is charged with the current flowing through the primary winding becomes equal to or greater than a predetermined voltage for reset determination, when the current flowing through the primary winding becomes equal to or greater than a predetermined current for reset determination, when a differential voltage between the voltage of the capacitor and a previous voltage of the capacitor becomes equal to or greater than the predetermined voltage for reset determination, when a differential current between the current flowing through the primary winding and a previous current flowing through the primary winding is equal to or greater than the predetermined current for reset determination or when a predetermined time elapses since the current starts flowing through the primary winding, then it is determined that the welding transformer is in the reset allowing state and the on-signal is supplied to the bypass switching element.
13. The method according to claim 9 , wherein bias magnetism does not proceed in the welding transformer during the reset allowing state, even if a welding process is carried out continuously.
14. The method according to claim 9 , wherein no current flows in the bypass switching element before the welding transformer is brought into the reset allowing state.
15. The method according to claim 9 , wherein the primary winding has a larger impedance than the bypass switching element.