Can I use WestBengal Govt EWS certificate for central Govt jobs ?
As per most of the central government job notifications in general there are no such mentions of state and central government EWS. In general it is provided that a applicant who is applying for the job needs to provide the certificate in a provided time. So you don't have to worry about it and you can obviously submit the EWS certificate for central government jobs.
Also before apply you should thoroughly check the notification of central government job you wish to apply in. If it is separately provided that you have to provide the EWS certificate issued by central government then you have to do it else you can go with the state government certificate.
I hope this answer helps. All the very best for your future endeavors!