If synchronous motors installed , it will reduce the electric bill of the industry. Why?

First, you need to check with your utility company what they bill you for. Generally utility companies bill you for kwh (kilo watt hour) and kvarh (kilo volt ampere reactive) but some utility companies may not charge you for kvarh. In such a case it is useless to install a synchronous motor. Synchronous motors and capacitor banks when installed in parallel with the incoming utility feeders reduce the reactive power (kvar) drawn from the system.