Motor starter idea

It's obvious that English is not your primary language, but I for one am having difficulty understanding your question. Can you try to provide more information?

Are you asking why someone would have two pumps in series as a booster station? If so, it is not an electrical issue, it is a mechanical one.

thanks for your reply

yes english languge my second languge but i think this is not make different

how do you know that ?

any how

what i need to know is why we do use the motor starter i mean in big pumps we should provide motor starter panel in switchgear why we don't use it in the small pumps ?

your cooperation is highly apperciated

The power to start a large motor (especially a compressor) is much greater (order of 6X) than the power to keep it running, even under fully rated mechanical load. Some motors have "starter' windings and a centrifugal switch to disconnect them once the motor is up to speed (otherwise they may burn up). Some motors require a separate, higher rated starting feed input. It does not pay to guess - check with the manufacturer's instructions and specifications if in doubt.