I have Glycol Pumps installed at my plant for glycol circulation. The pump motor is inverter duty motor rated 40HP, 480V, 1775 RPM & 48.2 Amps. The motor is run through a VFD as the circulation rate is not fixed but the speed is controlled manually (not a feedback control loop). The motor is currently running at 800 rpm but the rpm needs to be decreased. Up to what minimum rpm I can run the motor safely?