2Y-Y-2△-△ connection four-speed motor contactor control circuit

The circuit is shown in Figure 3-120. If the motor capacity is small (rated current is less than 5A), an intermediate relay
(with a larger number of contacts) can be used instead of the contactor. This circuit can realize forward operation at four speeds and the highest speed reverse operation. The
circuit is interlocked through the normally closed auxiliary contacts of each contactor to ensure that two speeds cannot be started at the same time and cause a short circuit
accident . This circuit allows pressing any start button to immediately obtain the corresponding speed without having to press the stop button in advance,
and without having to consider the speed of the motor during operation. In the figure, SB1 and SB6, SB2 and SB7, SB3 and SBs, SB4 and
SBa, SBs and SBao are all linkage buttons.