AC Contactors

ok let me try

there is a coil in contractors when this coil energize it acts like a magnet and that is why they attract power contacts.contactor does not have any kind of rectifier circuit.

i thinks this is it if not tell me so

Thank u very much KJK/USA.

"For contactors energized with alternating current, a small part of the core is surrounded with a shading coil, which slightly delays the magnetic flux in the core. The effect is to average out the alternating pull of the magnetic field and so prevent the core from buzzing at twice line frequency"

This actually I had through before ,but couldn't get how i actually happens.

If you could,pls clarify.

Can 220V dc in switchboards be replaced with 220V ac?.Can the relays be manufactured for 220v ac control supply?

I know this may be some silly questions!.

Re: If you could,pls clarify. <shading coil>

I googled on ["shading coil" explanation diagram] and got 4700 or so hits. The first one is this--it's a little technical and the diagram is a little hard to see, but it may provide the clarification you need.

In my simple terms, the AC magnetic field from the part of the magnetic core not surrounded by the shading coil is at a certain phase angle. The shading coil adds some inductance around part of the magnet, which changes its phase angle relative to the other part of the magnetic field. With the two fields somewhat out of phase, you avoid a point in time (120 times a second) when the magnetic field is zero.

Re: Can 220V dc in switchboards be replaced with 220V ac?.Can the relays be manufactured for 220v ac control supply?

Well, generally speaking, yes. How easy and whether doing it serves a worthwhile function are the real questions. If you seriously want to do that (and what some help) you'll need to tell us a lot more.

I can't immediately think of a good reason for doing that. If I was stuck with an AC source and still had a good reason for running the DC switchboard, I'd be more inclined to rectify the AC to make DC and run the panelboard using that.

just noticed this topic..

Can 220V dc in switchboards be replaced with 220V ac?.Can the relays be manufactured for 220v ac control supply?

Yes you can get 220v AC coils, you can also get 440volts ones too! The only problem with converting DC to AC and using the existing contactors with their coils is they will chatter. You have already been given an excellent explanation of why shading rings/coils are used on AC contactor coils, so if you intend to power your existing switchboard with AC, change out the coils only. But why would you convert?