Normally, when a high flow rate causes the pump motor to trip off-line it is due to the motor not having enough horsepower to allow the pump to reach the end of its curve. You could check the pump curve to determine where the pump hydraulic horsepower required matches the horsepower of the motor supplied.
I have heard about this when the unit requires two heater feed pumps to be on line at a time. The proposed solution was to put a pressure control on the heater feed pump discharge that closed off the pass flow control valves to keep the pressure on the heater feed pump high enough to prevent the pump from tripping the motor. I do not have any experience with this arrangement as we installed a large enough motor so that this would not be a problem.
