Multi-purpose thyristor rectifier and speed regulating circuit

This power supply has the following uses.
    ① Provide a 0-220V adjustable DC power supply, which can be used to adjust the speed of tens of kilowatts of DC motors. In addition,
a 170V 3A non-adjustable DC power supply is provided, which can be used as the excitation power supply of the DC motor or the arc starting power supply of the electric welding machine.
    ②After appropriate switching, a low voltage and high current of 350V, O~lfl;OA can be supplied for DC welding.
    In the figure, voltage relay KAi is used to prevent overcurrent when the motor reverses at high speed; voltage loss relay KA2 is used to
protect against loss of excitation and prevent overrun.