Starter Contactor Rating

Not possible without knowing a bucketful of information that hasn't been supplied.

There is no way that British Standard 7671 is unavailable in that pert of the world.

Presumably they are rated at the voltage and current of a 22Kw star delta starter, what ever they may be.

Contactor ratings will also depend on the short circuit protection by fuse or MCCB Most of the switchgear manufacturers have given chart based type 2 coordination for Contactor selection . Please refer these are available in the Internet

The contactor rating selection will depends of you contactor position in you Star/Delta construction.

I do not recommend referent to motor power ( data commonly use ) but more to current draw by motor in regards of his nominal voltage.

As you may be already know for the same motor rating in kW you may have different current level in regard of voltage.

The current level in regard of shall be printed on the motor name plate.

When you get the nominal line current the contactor rating selection is easier. You will have bellow a Star/Delta construction Type 2 coordination

Generally Line contactor ( KM1 ) is rated for nominal line current and the Star contactor ( KM3 ) is also rated for this line nominal current

Concerning Delat contactor (KM2 ) we can select a contactor able to sustains nominal line current divided by 1.732 ( square root of 3 )

Then to avoid fast wear or issue in your Star/Delta starter I will strongly recommend to use mechanical interlock between Star and Delta contactor ( you will avoid to switch them in the same time ) and associate to this mechanical interlock an electrical interlock.

I will strongly recommend using both interlock mechanical and electrical to have a reliable installation.

I will also strongly recommend to scrupuluously follow phase order to avoid transiant voltage when you swich from Star to Delta mode.

I see also there is some reference to contactor rating is related to short rating protection. This is important when you are using coordination table.

In the schematic bellow the overload protection shall be rated for line nominal current.

It is important to know each manufacturer generate coordination table and you shall scrupulously follow product association listed in these table to have the coordination type mentioned in the table.

Hope this will answer to your request.

I notice I have done an inversion in my previous post.

You should replace Star contactor ( KM3 ) by Delta contactor ( KM3 ) and also Delta contactor ( KM2 ) by Star contactor ( KM2 )

I really appologize for this error.