Abstract: The present invention discloses a system for pumping a fluid into a common pressure outlet. The system contains a plurality of reciprocating pumps. A separate sensor coupled to one cylinder of each pump provides an electrical signal each time the piston in that cylinder is at a predetermined position. A speed control circuit is provided to independently adjust the speed of each pump. Manual speed control for each pump is provided through a separate throttle for each pump. A pump control circuit coupled to each of the throttles, sensors and speed control circuit controls the operation of the system. An operator determines which of the pumps to operate by closing appropriate bypass switches provided at the pump control circuit, turns on the first (master) pump and adjusts its associated throttle to operate the pump at a desired speed. The operator then turns on each of the remaining (slave) pumps.

Abstract: An apparatus and method for controlling a motor used for rotating a drill stem is disclosed. Silicon control rectifier based system regulates the power to the motor. A control unit coupled to the SCR regulator and the motor monitors the motor input current, voltage and speed levels. If during operation the motor current exceeds a predetermined value and at the same time the motor voltage or speed falls below a predetermined value, the control unit activates an alarm condition and causes the SCR regulator to controllably ramp down the current supply to the motor and then reduces the motor speed reference.