Solid state relay motor drive circuit

Circuit working principle:
    (1) Soft start control: During the starting time, the DC current of the XSSR primary
increases linearly from zero to control the current of the secondary AC motor so that it increases linearly
from zero to the rated value. , thereby achieving soft start.
    The power-on delay function is composed of RP, cl delay components and inverting amplifier. The moment the power is turned on
, the electrolytic capacitor C. The voltage on is zero,
the voltage at the input terminal of the inverting amplifier gradually decreases from +12 V, and the voltage at the output terminal gradually increases from ov. The length of the delay
is determined by hydrazine'. adjust. The normally closed contact of the relay is connected in parallel at c. The purpose is
to discharge the charge on the capacitor immediately after shutting down .
    (2) Phase failure protection: The three-phase power supply
is sent to the primary of the optocoupler and the indicator light emitting diode through the voltage-reducing resistor, bridge rectifier and voltage regulator tube ZD respectively. Three optocouplers
are connected in secondary series. As long as a phase failure occurs or the voltage of a certain phase is lower than 180 V,
all three-phase power will be automatically cut off and the indicator light-emitting diode will go out.
    (3) Balance adjustment and voltage setting: RP. , RPs, and RP6 respectively fine-tune
the primary current of XSSR to balance the three phases. RP2 is used as the initial voltage setting, which determines
the voltage on the load at the moment of startup, and is generally set as Ov. RP3
is not determined as the final output voltage. It determines the working voltage after the motor
enters a stable state and can be adjusted according to actual needs.