Cam controller starting circuit

158. A cam controller is often used to control the starting, speed and forward and reverse rotation of a winding asynchronous motor with a small capacity.
    The cam controller starting circuit is shown in Figure 3-158. The cam controller handwheel has a total of 11 positions (see the contact opening and
closing table in the figure). The middle position is "0", and the motor does not move. There are five positions on the left and right, indicating the opening and closing status of the contacts during forward and reverse rotation
. "×" in the table indicates that the contact is closed, and the absence of this mark indicates that the contact is open. The cam controller has a total of 12 pairs of contacts. The top
4 pairs of contacts SAi~SA4 are used to control the forward and reverse rotation of the motor. The 4 contacts are equipped with arc extinguishing covers; the middle 5 pairs of contacts
xZl~x25 are used as switching resistors. Use; the bottom three pairs of auxiliary contacts SAs~SA7 are used in the control circuit.