Three phase controlling system

In a three phase load control system including:

• first and second bilateral switching circuits respectively connected in two of the three phase lines between a load and a power supply therefor,
• trigger means for applying gating signals to said first and second bilateral switching circuits, and
• a synchronizing circuit for providing electrical signals in synchronism with the frequency of the power supply voltage for said trigger means to provide a prescribed time base from which retard angles for the gating signals from said trigger circuit are referenced,
• the improvement wherein said synchronizing circuit contains means for controlling said trigger means so that the gating signals, which are applied to the one of said bilateral switching circuits which is connected in the one of said two phase lines having the later phase, are advanced by a constant degree with respect to said later phase, and the gating signals, which are applied to the other of said bilateral switching circuits, are synchronized with the phase of the phase line in which said other bilateral switching circuit is connected, and wherein said synchronizing circuit comprises a three phase transformer having
• primary windings connected in a Y-configuration to the three-phase lines of said power supply,
• a first secondary winding associated with the primary winding of the phase of the phase line in which said other bilateral switching circuit is connected, and providing the time base control of said trigger means for the gating signals for said other bilateral switching circuit, and
• second and third secondary windings, associated with the other two phases of the remaining two phase lines, connected in series and providing the time base control of said trigger means for the gating signals for said one bilateral switching circuit.

In a three phase load control system including:

• first and second bilateral switching circuits respectively connected in two of the three phase lines between a load and a power supply therefor,
• trigger means for applying gating signals to said first and second bilateral switching circuits, and
• a synchronizing circuit for providing electrical signals in synchronism with the frequency of the power supply voltage for said trigger means to provide a prescribed time base from which retard angles for the gating signals from said trigger circuit are referenced,
• the improvement wherein said synchronizing circuit contains means for controlling said trigger means so that the gating signals, which are applied to the one of said bilateral switching circuits which is connected in the one of said two phase lines having the later phase, are advanced by a constant degree with respect to said later phase, and the gating signals, which are applied to the other of said bilateral switching circuits, are synchronized with the phase of the phase line in which said other bilateral switching circuit is connected, and wherein said synchronizing circuit comprises three impedance elements connected in a Y-configuration to the three-phase lines of said power supply, the opposite ends of the impedance element which is connected to the phase line in which said other bilateral switching circuit is connected providing the time base control of said trigger means for the gating signals for said other bilateral switching circuit, and the ends of the remaining two impedance elements which are connected to the remaining two phase lines providing the time base control of said trigger means for the gating signals for said one bilateral switching circuit.