Analysis of the one-button start and stop circuit of the motor

There are many kinds of motor control circuits. Friends who like circuit research often like to ponder various control circuits. While satisfying their own hands-on ability, they also have a full sense of accomplishment.

What I want to share with you today is the classic circuit - one-button start and stop. Many friends say that this circuit is not very practical. But it is indeed used in work.

For example, many belt-driven production lines use one-button start and stop. For non-standard manufacturers who consider cost, saving material costs is the best way.

Well, without further ado, I will go straight to the diagram and explain. There are currently two versions of this circuit diagram, let's take a look at them one by one.

The components to be used are two intermediate relays and one contactor (two open and one closed auxiliary contacts). The contactor drives the motor to operate and control related equipment. The intermediate relay is responsible for start-stop coordination conversion.

Circuit analysis: Press the SB start button (remember this button is a self-resetting normally open button) ➠ KM normally closed auxiliary contact ➠ KA2 relay normally closed contact ➠ to KA1 relay coil ➠ KA1 related contacts will move.

The third KM upper KA1 normally open contact is closed ➠ KA2 normally closed ➠ KM coil ➠ energized and attracted ➠ upper KM auxiliary normally open contact self-protection ➠ motor running. At this time, releasing the SB button will not affect KM, because it is energized and skips the control range of SB.

When SB is released, remember that KA1 will be de-energized, that is, the relevant contacts are still reset. The difference is that the state of the KM auxiliary contacts in the first and second circuits has changed (this is the key point).

Since the status of each contact has changed when km is started, it indirectly paves the way for kA2 to be energized. When the button is pressed again, KA1 is blocked, KA2 is used, and the closed contact of km No. 6 is passed, KA1 is normally closed, KA2 coil, KA2 is energized, and the relevant contacts should be activated, and the KA2 auxiliary contact on the 3-way KM coil is disconnected, which causes the KM coil to lose power, the self-protection is released, and the motor stops.

After km loses power, its related contacts return to their initial state to prepare for the next start. So far, a working cycle - one-button start and stop is completed.

The picture below is another version, which is actually almost the same, just in a different position.