High power motor simple program control circuit

The working principle of the circuit (only the relevant parts in manual mode are drawn): Figure a
shows the principle of the primary loop circuit; Figure b shows the traditional typical secondary circuit
circuit ; Figure e shows the improved version with program mandatory nature Secondary circuit schematic
diagram. First, analyze the shortcomings of the traditional secondary circuit.
Judging from the circuit form in Figure b, it seems to be completely reasonable, and everyone is familiar with its working principle. However
, among many operators, the quality is different. Suppose that an operator mistakenly presses the run
button to start the equipment. From the principle of Figure b, when the QAz run button is pressed, even
if the equipment is pressed through the QA, start button according to the operation procedure of starting first and then running, the above
misoperation can completely cause the running contactor C: to enter the working pull-in state. The state becomes
direct start, causing the starting current to be very large at this time and damaging the equipment. For this reason, the author designed
the circuit shown in Figure c, which can completely prevent the occurrence of the previous accident.