Soft starting method and system thereof in the way of wave-skipping with stepped frequency and stepless voltage regulating for a motor

A system configured for using a soft starting method in the way of wave-skipping with stepped frequency and stepless voltage regulating for a motor, characterized in that:

• the method includes:
• trigger signals generated by a control system act on five sets of anti-parallel thyristor valves connected between a power supply and the motor to conduct a pair of thyristors thereof according to a set frequency and a set sequence, and
• the motor is started from a standstill status to full speed in the way of wave-skipping by controlling the sets of the thyristor valves to realize the maximum torque of the motor, and make the motor complete the starting from a static state to full speed, and the system comprises:
• an actuator and a control device, wherein
• the actuator includes a plurality of sets of thyristor valves, with the two thyristors from each set of thyristor valves forming an anti-parallel group, connecting between the power supply and the motor, and
• the connections include:
• a 1st set of valves connected between the power network and the motor through a input end and a 1st output end;
• a 2nd set of valves connected between the power network and the motor through a 2nd input end and a 2nd output end;
• a 3rd set of is valves connected between the power network and the motor through a 3rd input end and a 3rd output end;
• a 4th set of valves connected between the 3rd input end and the 2nd output end;
• and a 5th set of valves connected between the 2nd input end and the 3rd output end.

A soft starting method in the way of wave-skipping with stepped frequency and stepless voltage regulating for a motor, wherein:

• trigger signals generated by a control system act on five sets of anti-parallel thyristor valves connected between a power supply and the motor to conduct a pair of thyristors thereof according to a set frequency and a set sequence, and
• the motor is started from a standstill status to full speed in the way of wave-skipping by controlling the sets of the thyristor valves to realize the maximum torque of the motor, and make the motor complete the starting from a static state to full speed,
• wherein setting the frequency and sequence includes:
• firstly, while starting, selectively removing half-waves in a waveform of the supply source by means of a ¼f trigger signal, making the fundamental wave of the voltage of the motor become ¼ of the power frequency, and making the voltage steadily increase to ¼ rated voltage, to realize the motor starting from 0 Hz to 12.5 Hz;
• secondly, selectively removing half-waves in the waveform of the supply source, by means of a ½f trigger signal, making the fundamental wave frequency of the voltage and current of the motor become ½ of the power frequency, to making the rotation speed of the motor increase in full speed from ¼, to realize the motor starting from 12.5 Hz to 25 Hz;
• and
• thirdly, applying all of the half-waves of the waveform of the supply source to the motor, through the trigger signal of the power frequency, making the rotation speed increase in full speed from ½, to realize the motor starting from 25 Hz-50 Hz;
• wherein the method of half-wave removal selection includes:
• a step (1) of:
• dividing a cluster of 6 trigger signals from the control system into 3 groups respectively connecting the sets of valves of the actuator, wherein each set of valves has two signals at the same time, the starting points of the signals from the adjoining two groups are at intervals of a rated cycle, and conduction is in accordance with the following sequences:
• a first 1st set of valves is in positive conduction and a 3rd set of valves is in opposite conduction simultaneously;
• a 2nd set of valves is in positive conduction and the 1st set of valves is in opposite conduction simultaneously;
• and the 3rd set of valves is in positive conduction and the 2nd set of valves is in opposite conduction simultaneously, and the fundamental wave frequency of AC voltage at the output end is made to be approximately ¼ of a rated frequency;
• and
• a step (2) of:
• the cluster of 6 trigger signals from the control system is divided into 3 groups respectively connecting the sets of valves of the actuator, wherein each set of valves has two signals at the same time, the starting points of the signals from the adjoining two groups are at intervals of a rated cycle, and conduction is in accordance with the following sequences:
• a 1st set of valves is in positive conduction and a 5th set of valves is in opposite conduction simultaneously;
• a 4th set of valves is in positive conduction and the 1st set of valves is in opposite conduction simultaneously;
• the 5th set of valves is in positive conduction and the 4th set of valves is in opposite conduction simultaneously, and the fundamental wave frequency of AC voltage at the output end is made to be approximately ½ of a rated frequency.