One of the zero-trigger thyristor power adjustment circuits

The output waveform of the thyristor zero trigger circuit is a sine wave, so it does not produce electromagnetic interference like the phase shift trigger circuit
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This is the basic circuit for zero trigger thyristor power regulation . In the figure, the voltage regulator tube VS acts as a clamp and provides a path for charging the capacitor Ci; the function of VD is to prevent the capacitor Cz from reverse charging during the negative half cycle of the power supply; the resistors Rz and R4 are current-limiting resistors to limit the control electrode current. In the figure, the power-on time 1 and the power-off time 2 depend on the opening and closing time of the switch (or control contact) SA. That is, the load power is controlled by SA .