Abstract A method of starting a current-fed inverter used as a high-frequency induction heating power supply and having a DC cut-off capacitor in the load circuit first supplies successive gate pulses which are spaced apart by small periods of time to a pair of thyristors of a power inverter unit until a turn-on current for the thyristors exceeds a latching current. When a voltage between output terminals of the power inverter unit reaches a predetermined thyristor reverse-biasing voltage, the successive gate pulses are no longer supplied to the thyristor pair. Then, successive gate pulses are supplied to a another pair of thyristors of the power inverter unit. The foregoing operation is repeated for successive thyristor pairs in a predetermined order until the period of oscillation of successive gate pulses supplied to the thyristor pairs is progressively shortened into conformity with a prescribed inverter oscillation period. With this method, no starter (with separate power supply) is required, and the prescribed inverter oscillation period can be quickly and reliably reached.
A method of starting a current-fed inverter with self-excitation for supplying AC power to an inverter load having a DC cut-off capacitor, the current-fed inverter having a power inverter unit composed of a plurality of thyristors and having AC output terminals, said starting method comprising the steps of: (a) applying successive gate pulses to a pair of the plurality of thyristors from a time when a starting signal is generated at least until a turn-on current for the pair of thyristors exceeds a latching current; (b) detecting a voltage between the AC output terminals and comparing the detected voltage with a preset voltage corresponding to a thyristor reverse-biasing voltage; (c) generating a pulse each time the detected and preset voltages are equal to each other; and (d) supplying gate pulses in synchronism with the generated pulses to the thyristors of the power inverter unit in a prescribed order until a period of oscillation of the gate pulses is equal to a predetermined inverter oscillation period.
Claim 2
Independent Claim
165 words
A method of starting a current-fed inverter with self-excitation for supplying AC power to an inverter load having a DC cut-off capacitor, the current-fed inverter having a power inverter unit composed of a plurality of thyristors and having AC output terminals, said starting method comprising the steps of: (a) applying successive gate pulses to a pair of the plurality of thyristors from a time when a starting signal is generated at least until a turn-on current for the pair of thyristors exceeds a latching current; (b) detecting a voltage between the AC output terminals and comparing the detected voltage with a preset voltage corresponding to a thyristor reverse-biasing voltage; (c) generating a pulse each time the detected and preset voltages are equal to each other; and (d) supplying gate pulses in synchronism with the generated pulses to the thyristors of the power inverter unit in a prescribed order until a period of oscillation of the gate pulses is equal to a predetermined inverter oscillation period.
Claim 3
Dependent Claim
40 words
A method according to claim 1, wherein the first pulse of the gate pulses supplied to the thyristors of the power inverter is arranged so as to maximize an initial DC voltage within the current-fed inverter output by the thyristors.
Claim 4
Dependent Claim
43 words
A method according to claim 1, wherein the step of applying successive gate pulses comprises supplying a burst of gate pulses from a burst pulse generator such that the period of the burst of pulses is much shorter than the inverter oscillator period.