overload relay

No you should not do that. An MCB is designed for short circuit protection whereas an oveload relay protects from over-current conditions persisting for some time.So use both. Electronic relays have more protection features than mechanical thermal overload types - so it is prefarable to use the former.
Seimens India & Seimens Germany provide a vide range of overload cum MCB suitable for motors up to a limited kw capacity. The exact suitable match to your requirement can be looked in to their catalog, look for 3uv-- serese.
You may, but this should strictly be a "For the Time Being Arrangement". Choose a MCB of current rating 5 times higher than the motor rated current.
You might want to explore what most major manufacturers now call a self protected motor starter. These are actually IEC style circuit breakers. UL has now approved them as both overload and overcurrent protection if applied correctly. In most cases the voltage to ground must be 300 volts or less. In other words if the supply is 480 volts, it must be wye connected. I know for a fact that AB, Siemens, and Sprecher & Schuh all have UL Listed models available.
MCB stands for Motor Circuit Breaker or also called a MPCB - Motor Protective (Protection) Circuit Breaker.

A MCB is a circuit breaker which is designed to provide both fault protection and overload protection for a motor in a single unit.

Here are some examples:


Bill Mostia
William(Bill) L. Mostia, Jr. P.E.
Worldwide Excellence in Dependable Automation
[email protected] (b) [email protected] (h)
www.exida.com 281-334-3169
These opinions are my own and are offered on the basis of Caveat Emptor.

Bouchard, James \[CPCCA\]

I would take exception to saying that a 480 wye connected system is operating at less than 300 volts. Also you would have a problem finding motors that operate at that voltage.

James Bouchard