Basics of ac contactors

[sam_s.pitt]

I know that in a typical ac contactor ac power generates a magnetic field and pulls a movable electromagnet to close contacts. The question is that when the ac power changes the polarity, the magnetic field vanishes, so why contacts do not open? (of course not exactly at the time when the voltage=0, due to hysteresis, but there is a moment in which the magnetic field in electromagnet parts is zero and they do not pull each other).

 

[FlapJack]

https://www.electro-tech-online.com/threads/how-is-an-a-c-relay-works.24186/

"An AC-powered relay has what is known as a "shading coil" (Google), which is a shorted turn on the relay's solenoid. A current is induced in this shorted turn which is 90 degrees out of phase with the main coil's current, and provides just enough magnetic field to keep the armature engaged during the zero crossing of the current in the main coil."

 

[smijesh]

A ring will be placed parallel to the axis of solenoid in all AC solenoid actuator. This is the major difference between AC solenoid and DC solenoid actuator. If AC exited to the main coil and magnetic force generated in the solenoid, the plunger pulls. At the same time induced current flow in the ring and generate the magnetic field opposite to the main solenoid coil. While negative cycle of AC magnetic field generated by the ring and main solenoid coils cancels each other, this sequence follow every cycle of AC. So no chattering due to AC