How to interlock and size selection of AC contactor?

How to interlock and size selection of AC Contactor?

Ac contactors work by using electromagnetic force and spring force to connect and disconnect contacts. Ac contactor has two working states: power off (release) and power on (action). When the attraction coil is energized, the static iron core generates electromagnetic attraction, the armature is attracted, and the connecting rod connected with the armature drives the contact to move, so that the normally closed contact circuit breaker is energized; When the attraction coil is powered off, the electromagnetic attraction disappears, the armature is reopened, the normally open contact is closed, the position spring is released, all contacts are reset, and the contactor is in the power off state.

Ac contactors are used to connect and disconnect loads. It is combined with thermal overload relays to protect operating electrical equipment. Combined with relay control loop, remote control or interlock related electrical equipment. Working principle of anti-sway AC contactor When the coil of anti-sway AC contactor is energized, the coil current will generate a magnetic field, so that the static iron core will generate electromagnetic attraction to attract the moving iron core, driving the AC contactor, normally closed contact is disconnected, normally open contact is closed, the two are interrelated.

When the coil is powered off, the electromagnetic attraction disappears, the armature is released under the action of the release spring, so that the contact is restored, normally open contact is disconnected, normally closed contact is closed. DC contactors work in a similar way to temperature switches. The interlocking mode is that the normally closed contact of KM1 anti-dazzle AC contactor is in series with the coil circuit of KM2 anti-dazzle AC contactor, and the normally closed contact of KM2 anti-dazzle AC contactor is in series with the coil circuit of KM1 anti-dazzle AC contactor.

However, if the contacts of the AC contactor are welded, the electrical interlock will not work. Therefore, mechanical interlocking contactors must also be used where there are strict requirements. The two anti-sway AC contactors put their auxiliary normally closed contact reserves into the control circuit on the other side and lock each other so that the two anti-sway AC contactors cannot be pulled in at the same time.

This circuit is relatively simple. The general principle is to ensure that the motor can not be connected when it is rotating forward, and can not be connected when it is rotating forward. Otherwise, the anti-swinging AC contactor will short-circuit the three-phase AC at the lower mouth of the contactor at the same time, and locking should be added in the circuit. In addition, both forward rotation and reverse rotation need to stop the motor at any time, so the stop button should be in series, the start button should be in parallel.

Therefore, the normally closed contacts of KM1 are in series in the KM2 coil circuit, and the normally closed contacts of KM2 are in series in the KM1 coil circuit. Once KM1 gains forward power, KM2 cannot gain power, thus objectively preventing the occurrence of short circuit accidents.

We have many years of experience in the ac contactor industry and can introduce relevant content to you from different aspects. If you are interested in ac contactor, you can contact us.